Research in
Res Exp Med (1992) 192:367-372
Experimental Medicine 9 Springer-Verlag 1992
Gastric mucosal blood flow distribution in the CCl4-induced cirrhotic rat a model of portal hypertensive gastropathy? K. Kotzampassi and E. Eleftheriadis Department of Surgery, University of Thessaloniki, GR-54006 Thessaloniki, Greece Received December 12, 1991 / accepted May 20, 1992
Summary. Because the carbon tetrachloride-induced cirrhotic rat model is considered to be the closest to the clinical situation of the cirrhotic patient, the discovery of congestive gastropathy in such rats would enable the development of a useful research model. By the use of laser-Doppler technology, gastric mucosal blood flow was assessed on 14 defined points of the stomach in 16 cirrhotic and 16 matched healthy rats, in an effort at in vivo mapping of the gastric mucosal microcirculation. Our findings of mucosal congestion in the cirrhotic stomach (reduced mucosal blood flow in the gastric corpus) are well matched with the distribution of gastric mucosal blood flow in the cirrhotic patient. These findings suggest that a rat's gastric mucosa could be used for studies of portal hypertensive gastropathy.
Key words: Experimental cirrhosis - Gastric mucosal blood flow - Laser-Doppler flowmetry
Introduction It is well established that there are congestive morphological and microcirculatory changes in the gastric mucosa in portal hypertension patients having welldeveloped portal venous collaterals due to hyperdynamic circulatory state characterized by increased cardiac output and peripheral vasodilation [2, 9, 10, 17, 18, 21, 24]. Similar morphologic and functional changes produced by portal vein ligation have been described in a portal hypertension rat model [27, 28, 30], but the relationship between the hemodynamic circulatory state and level of gastric mucosal perfusion is still a matter of controversy [13, 20, 25], Although the model of portal hypertensive rat due to carbon tetrachloride (CCl4)-induced liver cirrhosis is closer to the clinical situation of the cirrhotic patient [19], few data are available about its influence on the gastric mucosal microvasculature and microcirculation [20]. Correspondence to: E. Eleftheriadis
368 T h u s , t h e o b j e c t i v e o f t h e p r e s e n t s t u d y w a s to d e t e r m i n e t h e m i c r o c i r c u l a t o r y a l t e r a t i o n s o b s e r v e d in t h e g a s t r i c m u c o s a of t h e C C 1 4 - i n d u c e d c i r r h o t i c rat in r e l a t i o n to t h a t o f t h e health}, rat. T h e n o n - i n v a s i v e l a s e r - D o p p l e r t e c h n i q u e w a s u s e d f o r this in v i v o m a p p i n g o f g a s t r i c m u c o s a l b l o o d - f l o w d i s t r i b u t i o n .
Materials and methods
Animals' Thirty-two male Wistar rats (200-240 g) were used in this study. The animals were housed together for a l-week adaptation period, kept at a room temperature of 24~ with an alternating 12-h light-dark cycle, and had free access to tap water and standard rat food. Animals were deprived of food 18 h before the experiment, but allowed free access to water.
induction of CCl4 cirrhosis Cirrhosis of the liver was induced in 4-week old rats (80-100 g) by s.c. injection of CC14 and olive oil in a 1 : 1 solution and in a dose of 0.2 ml/100 g b. wt. twice a week for 8 weeks, following a previously described method [16.29]. In order to shorten the time required to induce cirrhosis, the rats received phenobarbitone diluted in the drinking water (35 rag/100 ml) from 1 week prior to starting eel4 administration.
Laser-Doppler flowmetry The principle on which laser-Doppler flowmetry is based has been described elsewhere in detail [23]. The laser-Doppler flowmeter used was the Periflux PF2B (Perimed, Sweden) - a 2mW helium-neon laser operated at 628.2nm - into which a fiberoptic probe (PF 302, 2.35 mm diameter) was plugged for the study. All measurements were performed with a signal processing Periflux filter at 4 kHz and the time constant of the output amplifier at 0.2 s, and expressed as perfusion units, 1 perfusion unit being equal to I V [23]. The laser-Doppler flowmetry readings were continuously transferred and stored through an A / D conventor (DT2801 series, Data Translation, Marlboro, Mass., USA) to a serially connected IBM PS2 personal computer running the Perisoft (Perimed, Sweden) software for further analysis and statistical processing.
Study design One week after termination of CCI~ 9-week treatment. 16 cirrhotic rats and 16 age-matched (14-week-old) controls were studied. After light pentobarbital-sodium (35 mg/kg b. wt.) anesthesia, a midline laparotomy was performed and an Angiocath 22G catheter was inserted into the caudal aorta to record arterial pressure. The portal vein was also cannulated with the same 22G catheter for portal pressure measurements in order to confirm the development of portal hypertension. Both catheters were secured in place by the use of cyanoacrylate glue and connected to highly sensitive pressure transducers S10/SI 1 (Gaeltec) respectively connected to a lineal pen recorder Multitrace 2 (Lectromed).
Gastric rnucosal microcirculation measurements During the same laparotomy, immediately after a stable pressure signal was received, the stomachs of both cirrhotic and control rats were dissected along the greater curvature from the forestomach to the first duodenal portion. A 5-ml 0.9% NaC1 rinse (37~ was gently poured on the mucosa for possible debris removal and the laser-Doppler probe was then placed against the mucosa at a standard distance of 0.6ram by means of a micromanipulator until optical coupling was achieved, which was identified by a green light signal on the flowmeter. Blood flow was measured for a 1-min period at each of 14 defined sites of the stomach (Fig. 1). The
369
Fig. 1. The 14 positions of the rat's stomach at which laserDoppler measurements were performed whole procedure lasted 20 min, after which the rats were euthanized. A segment of the liver was obtained for histological documentation of cirrhosis.
Statistical analysis All data were expressed as means • SD. Student's t-test for unpaired measurements was performed for statistical evaluation of the difference between the mean values of arterial and portal pressure in cirrhotics and controls. One-way analysis of variance was conducted using the one-factor ANOVA for repeated measurements (Stat-View, BrainPower, Calif,, USA) for comparison among the laser-Doppler flowmetry values in cirrhotics and controls. Probability values of P < 0.05 were considered as significant. Student's t-test for unpaired measurements was then conducted for comparison of the values between the respective points of measurements on the anterior and posterior stomach wall, both in cirrhotics and in controls, as well as between the same points of the stomachs of cirrhotics versus controls.
Results A l l 16 rats t r e a t e d with CCl4 e x h i b i t e d m a c r o s c o p i c a l l y m i c r o n o d u l a r cirrhosis, d o c u m e n t e d histologically. T h e m e a n p o r t a l p r e s s u r e of this g r o u p was 7.9 + 3.1 m m H g o r 229.16% h i g h e r t h a n for t h e c o n t r o l s (2.4 + 1 . 9 m m H g ) ( P < 0,001). H o w e v e r , t h e r e was n o significant d i f f e r e n c e in m e a n a r t e r i a l p r e s s u r e b e t w e e n cirrhotics (110 _+ 8.4 m m H g ) a n d c o n t r o l s (111 + 4.5 m m H g ) , which r e m a i n e d stable t h r o u g h o u t t h e p e r i o d o f t h e study. M e a n + S D signal levels at e a c h site o f t h e s t o m a c h in b o t h s t u d y g r o u p s a r e s h o w n in Fig. 2. B e c a u s e t h e S t u d e n t ' s t-test r e v e a l e d t h a t is no significant differe n c e b e t w e e n the a n t e r i o r a n d p o s t e r i o r walls at a n y p a r t i c u l a r p o i n t o f t h e
60
i
i
i
~
~
i
L
i
i
i
50
9~
40
~_ 2o ~0
I
3
!
I
I
I
4
5
6
7
points of measurement
Fig. 2. Gastric mucosal blood distribution in control versus cirrhotic rats. * P < 0.05; ** P < 0.001; D, controls; I , cirrhotics
370 stomach, only seven points of measurements are illustrated in Fig. 2. Corpus mucosal blood flow was significantly reduced in cirrhotics compared with controis and the distal stomach had a higher reduction of flow (P = 0.001) in relation to that of the proximal in cirrhotics versus controls (P = 0.05). In contrast to the corpus mucosal blood flow. antral blood flow exhibited a slight, but not statistically significant, increase. The greater curvature, which was highly perfused in controls, had a statistically significant decline in mucosal blood flow, in contrast to the lesser curvature, which - being purely perfused in normal rat exhibited a slight, but not statistically significant, increase in flow in cirrhotics. The highest significant difference in perfusion of all parts of the stomach was observed in the main portion of the anterior and posterior corpus mucosa, which being the highest perfused areas in controls - exhibited a highly statistically significant reduction in flow (34.7%). Discussion Splanchnic hemodynamic response to portal hypertension has been the subject of several recent studies [3, 4, 6, 9, 13]. According to these studies, it is now accepted that systemic circulation becomes hyperdynamic, that is, with increased cardiac output, splanchnic blood flow. and decreased vascular resistance. However, the effect of these hemodvnamic alterations on total and mucosal gastric blood flow is still controversial. The present study, conducted in portal hypertensive rats due to liver cirrhosis, revealed that corpus mucosal blood flow was significantly reduced, while antral mucosal blood flow was only slightly increased. Similar findings were also reported in cirrhotic humans with portal hypertensive gastropathy changes, the gastric mucosal blood flow being measured through the endoscope by use of the laser-Doppler technique [9, 11, 18]. In another clinical study, gastric mucosal hemodynamics were assessed by the use of the hydrogen clearance technique for blood-flow measurement and reflectance spectrophotometry for mucosal blood volume and oxygen saturation measurements: blood flow and oxygen saturation were found to be significantly decreased compared to control subjects, but gastric mucosal blood volume was unaltered [1]. These findings matched in well with the existence of a significantly increased number of open arteriovenous anastomoses, documented, in cirrhotic human stomachs (in the gastric corpus and not in the antrum) with casting techniques by Hashizume [15] as well as with the presence of dilated submucosal precapillaries, capillaries, and veins and straight pattern of arterioles, causing the gastric mucosa to have a mosaic-like appearance [10, 15, 17, 21, 24]. At experimental level, Manabe [20] also demonstrated a striking increase of gastric submucosal arteriovenous shunts in the gastric corpus, leading to the reduction of effective mucosal blood flow, both in portal-vein-ligated and in CC14induced cirrhotic rabbits. Nagamine et al. [22] and Satani et al. [26] also concluded that the decreased mucosal blood flow found in dogs was due to arteriovenous shunting induced by the hyperdynamic state. On the other hand, two other investigators studied gastric mucosal blood flow in a chronic portal hypertension rat model and found it to be increased [5, 25]. Geraghty et al. [13], working on a partially ligated portal vein model, showed by the use of autoradiography that corpus mucosal blood flow was significantly reduced 3 days after portal vein
371 ligation, but this reduction was not sustained at the 7th and 28th days, the level of perfusion being higher on the 28th day. They also found no significant difference of flow in the antral mucosa at any study period. The discrepancy between the results of all these studies could be explained by the differences (1) in the method of.portal hypertension production, (2) in the time of the study after portal hypertension establishment, and (3) in the bloodflow m e a s u r e m e n t technique used [27]. In recent work, Kravetz et al. [19] have documented that findings of studies in prehepatic models of portal hypertension are dissimilar to those in rats with portal hypertension due to cirrhosis of the liver. Our model of CC14-induced cirrhosis is considered to be closer to the clinical situation of the patients with liver cirrhosis, in both histological and functional aspects [12]. Although there is a discrepancy in the degree of portal-systemic shunt development, ranging from 0.2% to 85%, according to different studies [7, 8, 14, 31], this could be due to the different degree of disease evolution and the presence of ascites. In any case, it is evidence that there is a degree of flow increase towards the stomach [12, 19], a redistribution of the blood flow within the gastric wall [13], and a diminished microcirculation on the gastric corpus mucosa, exactly as also occurs in man. This finding in the CC14-induced cirrhotic rat seems to be of great clinical importance, because it appears it could be used as a model for the study of portal hypertensive gastropathy. As there is to date no experimental model of portal hypertensive or congestive gastropathy with a background of liver cirrhosis, further investigation could be planned for the pharmacological manipulation of this complex entity.
References 1. Adachi H, Maruyama M, Naito H, et al (1986) Study of gastric mucosal changes and mucosal hemodynamics in patients with liver cirrhosis. Dig Dis Sci 31 : $70 2. Baxter JN, Dobbs BR (1988) Portal hypertensive gastropathy. J Gastroenterol Hepatol 3 : 635-644 3. Benoit JN, Granger DN (1986) Splanchnic hemodynamics in chronic portal hypertension. Semin Liver Dis 6 : 287-298 4. Benoit JN, Granger DN (1988) Intestinal microvascular adaptation to chronic portal hypertension in the rat. Gastroenterology 94 : 471-476 5. Benoit JN, Womack WA, Kurthins RJ, Wilborn WH, Granger DN (1986) Chronic portal hypertension: effects on gastrointestinal blood flow distribution. Am J Physiol 250: G535539 6. Bosch J, Enriquez R, Groszmann RJ, Storer EH (1983) Chronic bile duct ligation in the dog: hemodynamic characterization of a portal hypertension model. Hepatology 3 : 10021007 7. Bredfeldt JE, Vorobioff J, Riley EM, Groszmann RJ (1983) Portal venous inflow modulates portal hypertension in cirrhotic rats: further evidence for the "forward flow" theory (abstr). Gastroenterology 84 : 1365 8. Caramelo C, Fernandez-Munoz D, Santos JC, et al (1986) Effect of volume expansion on hemodynamics, capillary permeability and renal function in conscious cirrhotic rats. Hepatology 6 : 129-134 9. Eleftheriadis E, Kotzampassi K, Alvanou A, Aletras H (1989) Blood flow and vascular changes in human portal hypertensive gastric mucosa. Hellenic J Gastroenterol 2: 284-289 10. Eleftheriadis E, Kotzampassi K, Tzartinoglou E, Alvanou A, Aletras H (1989) Congestive gastropathy and antral varices: is there an association? Endoscopy 21:208-211
372 11. Eleftheriadis E, Kotzampassi K, Aletras H (1990) The microcirculatorv status of portal hypertensive gastric mucosa in "normal" and post-sclerotherapy patients. Am J Gastroenterol 85 : 1538-1539 12. Fernandez-Munoz D. Caramelo C, Santos JC. et al (1985) Systemic and splanchnic hemodynamic disturbances in conscious rats with experimental liver cirrhosis without ascites. Am J Physiol 249 : G316-320 13. Geraghty JG, Angerson WJ, Carter DC (1989) Autoradiographic study of the regional distribution of gastric mucosal blood flow in portal hypertensive rats. Gastroenterology 97 : 1108-1114 14. Groszmann RJ, Vorobioff J, Riley EM (1982) Splanchnic hemodynamics in portal-hypertensive rats: measurements with labeled microspheres. Am J Physiol 242 : G156-160 15. Hashizume M, Tanaka K, Inokuchi K (1983) Morphology of gastric microcirculation in cirrhosis. Hepatology 3 : 1008-1012 16. Kitano S, Koyanagi N, Sugimachi K, Kobayashi M, Inokuchi K (1982) Mucosal blood flow and modified vascular responses to norepinephrine in the stomach of rats with liver cirrhosis. Eur Surg Res 14 : 221-230 17. Kotzampassi K, Eleftheriadis E, Aletras H (1990) The mosaic-like pattern of portal hypertensive gastric mucosa after variceal eradication by sclerotherapy. J Gastroenterol Hepatol 5 : 659-663 18. Kotzampassi K, Eleftheriadis E. Aletras H (1992) Gastric mucosal blood flow in portal hypertension patients - a laser-Doppler flowmetry study. Hepato-Gastroentero139 : 39-42 19. Kravetz D, Bosch J, Arderiu M, Pizcueta MP. Rodes J (1989) Hemodynamic effects of blood volume restitution following a hemorrhage in rats with portal hypertension due to cirrhosis of the liver: influence of the extent of portal-systemic shunting. Hepatology 9 : 808-814 20. Manabe T, Suzuki T, Honjo I (1978) Changes of gastric blood flow in experimentally induced cirrhosis of the liver. 8urg Gynecol Obstet 147 : 753-757 21. McCormack TT, Sims J, Eyre-Brook I, et al (1985) Gastric lesions in portal hypertension: inflammatory gastritis or congestive gastropathy? Gut 26:1226-1232 22. Nagamine K, Inokuchi K, Sakata H, et al. (1986) Development of erosive gastritis in a canine model of esophageal varices. Japan J Surg 16:218-224 23. Nillson GE (1990) Perimed's LDV flowmeter. In: Shepherd AP, Oberg PA (eds) Laser Doppler flowmetry. Kluwer, Boston, pp 57-72 24. Papazian A, Braillon A, Dupas J t , Sevenet F, Capron JP (1986) Portal hypertensive gastric mucosa: an endoscopic study. Gut 27 : 1199-1203 25. Pique JM, Leung FW, Kitahora T, et al (1988) Gastric mucosal blood flow and acid secretion in portal hypertensive rats. Gastroenterology 95 : 727-733 26. Santani H, Yaman H, Kakegawa T (1986) Studies on hemorrhagic gastritis after gastric devascularization using portal hypertensive dogs. Nippon Gakkai Zasshi 10:218-224 27. Sarfeh 1J, Tarnawski AS (1987) Gastric mucosal vasculopathy in portal hypertension (editorial). Gastroenterology 93:1129-1131 28. Sarfeh IJ, Tarnawski A, Hajduczek A, et al (1988) The portal hypertensive gastric mucosa: histologic, ultrastructural, and functional analysis after aspirin-induced damage. Surgery 104:79-85 29. Tamayo RP (1983) Is cirrhosis of the liver experimentally produced by CCI~ an adequate model of human cirrhosis? Hepatology 3:112-120 30. Tarnawski AS, Sarfeh IJ, Stachura J, et al (1988) Microvascular abnormalities of the portal hypertensive gastric mucosa. Hepatology 8 : 1488-1494 31. Vorobioff J, Bredfeldt JE. Groszmann RJ (1984) Increased blood flow through the portal system in cirrhotic rats. Gastroenterology 87:1120-1126
Res Exp Med (1992) 192:367-372
Experimental Medicine 9 Springer-Verlag 1992
Gastric mucosal blood flow distribution in the CCl4-induced cirrhotic rat a model of portal hypertensive gastropathy? K. Kotzampassi and E. Eleftheriadis Department of Surgery, University of Thessaloniki, GR-54006 Thessaloniki, Greece Received December 12, 1991 / accepted May 20, 1992
Summary. Because the carbon tetrachloride-induced cirrhotic rat model is considered to be the closest to the clinical situation of the cirrhotic patient, the discovery of congestive gastropathy in such rats would enable the development of a useful research model. By the use of laser-Doppler technology, gastric mucosal blood flow was assessed on 14 defined points of the stomach in 16 cirrhotic and 16 matched healthy rats, in an effort at in vivo mapping of the gastric mucosal microcirculation. Our findings of mucosal congestion in the cirrhotic stomach (reduced mucosal blood flow in the gastric corpus) are well matched with the distribution of gastric mucosal blood flow in the cirrhotic patient. These findings suggest that a rat's gastric mucosa could be used for studies of portal hypertensive gastropathy.
Key words: Experimental cirrhosis - Gastric mucosal blood flow - Laser-Doppler flowmetry
Introduction It is well established that there are congestive morphological and microcirculatory changes in the gastric mucosa in portal hypertension patients having welldeveloped portal venous collaterals due to hyperdynamic circulatory state characterized by increased cardiac output and peripheral vasodilation [2, 9, 10, 17, 18, 21, 24]. Similar morphologic and functional changes produced by portal vein ligation have been described in a portal hypertension rat model [27, 28, 30], but the relationship between the hemodynamic circulatory state and level of gastric mucosal perfusion is still a matter of controversy [13, 20, 25], Although the model of portal hypertensive rat due to carbon tetrachloride (CCl4)-induced liver cirrhosis is closer to the clinical situation of the cirrhotic patient [19], few data are available about its influence on the gastric mucosal microvasculature and microcirculation [20]. Correspondence to: E. Eleftheriadis
368 T h u s , t h e o b j e c t i v e o f t h e p r e s e n t s t u d y w a s to d e t e r m i n e t h e m i c r o c i r c u l a t o r y a l t e r a t i o n s o b s e r v e d in t h e g a s t r i c m u c o s a of t h e C C 1 4 - i n d u c e d c i r r h o t i c rat in r e l a t i o n to t h a t o f t h e health}, rat. T h e n o n - i n v a s i v e l a s e r - D o p p l e r t e c h n i q u e w a s u s e d f o r this in v i v o m a p p i n g o f g a s t r i c m u c o s a l b l o o d - f l o w d i s t r i b u t i o n .
Materials and methods
Animals' Thirty-two male Wistar rats (200-240 g) were used in this study. The animals were housed together for a l-week adaptation period, kept at a room temperature of 24~ with an alternating 12-h light-dark cycle, and had free access to tap water and standard rat food. Animals were deprived of food 18 h before the experiment, but allowed free access to water.
induction of CCl4 cirrhosis Cirrhosis of the liver was induced in 4-week old rats (80-100 g) by s.c. injection of CC14 and olive oil in a 1 : 1 solution and in a dose of 0.2 ml/100 g b. wt. twice a week for 8 weeks, following a previously described method [16.29]. In order to shorten the time required to induce cirrhosis, the rats received phenobarbitone diluted in the drinking water (35 rag/100 ml) from 1 week prior to starting eel4 administration.
Laser-Doppler flowmetry The principle on which laser-Doppler flowmetry is based has been described elsewhere in detail [23]. The laser-Doppler flowmeter used was the Periflux PF2B (Perimed, Sweden) - a 2mW helium-neon laser operated at 628.2nm - into which a fiberoptic probe (PF 302, 2.35 mm diameter) was plugged for the study. All measurements were performed with a signal processing Periflux filter at 4 kHz and the time constant of the output amplifier at 0.2 s, and expressed as perfusion units, 1 perfusion unit being equal to I V [23]. The laser-Doppler flowmetry readings were continuously transferred and stored through an A / D conventor (DT2801 series, Data Translation, Marlboro, Mass., USA) to a serially connected IBM PS2 personal computer running the Perisoft (Perimed, Sweden) software for further analysis and statistical processing.
Study design One week after termination of CCI~ 9-week treatment. 16 cirrhotic rats and 16 age-matched (14-week-old) controls were studied. After light pentobarbital-sodium (35 mg/kg b. wt.) anesthesia, a midline laparotomy was performed and an Angiocath 22G catheter was inserted into the caudal aorta to record arterial pressure. The portal vein was also cannulated with the same 22G catheter for portal pressure measurements in order to confirm the development of portal hypertension. Both catheters were secured in place by the use of cyanoacrylate glue and connected to highly sensitive pressure transducers S10/SI 1 (Gaeltec) respectively connected to a lineal pen recorder Multitrace 2 (Lectromed).
Gastric rnucosal microcirculation measurements During the same laparotomy, immediately after a stable pressure signal was received, the stomachs of both cirrhotic and control rats were dissected along the greater curvature from the forestomach to the first duodenal portion. A 5-ml 0.9% NaC1 rinse (37~ was gently poured on the mucosa for possible debris removal and the laser-Doppler probe was then placed against the mucosa at a standard distance of 0.6ram by means of a micromanipulator until optical coupling was achieved, which was identified by a green light signal on the flowmeter. Blood flow was measured for a 1-min period at each of 14 defined sites of the stomach (Fig. 1). The
369
Fig. 1. The 14 positions of the rat's stomach at which laserDoppler measurements were performed whole procedure lasted 20 min, after which the rats were euthanized. A segment of the liver was obtained for histological documentation of cirrhosis.
Statistical analysis All data were expressed as means • SD. Student's t-test for unpaired measurements was performed for statistical evaluation of the difference between the mean values of arterial and portal pressure in cirrhotics and controls. One-way analysis of variance was conducted using the one-factor ANOVA for repeated measurements (Stat-View, BrainPower, Calif,, USA) for comparison among the laser-Doppler flowmetry values in cirrhotics and controls. Probability values of P < 0.05 were considered as significant. Student's t-test for unpaired measurements was then conducted for comparison of the values between the respective points of measurements on the anterior and posterior stomach wall, both in cirrhotics and in controls, as well as between the same points of the stomachs of cirrhotics versus controls.
Results A l l 16 rats t r e a t e d with CCl4 e x h i b i t e d m a c r o s c o p i c a l l y m i c r o n o d u l a r cirrhosis, d o c u m e n t e d histologically. T h e m e a n p o r t a l p r e s s u r e of this g r o u p was 7.9 + 3.1 m m H g o r 229.16% h i g h e r t h a n for t h e c o n t r o l s (2.4 + 1 . 9 m m H g ) ( P < 0,001). H o w e v e r , t h e r e was n o significant d i f f e r e n c e in m e a n a r t e r i a l p r e s s u r e b e t w e e n cirrhotics (110 _+ 8.4 m m H g ) a n d c o n t r o l s (111 + 4.5 m m H g ) , which r e m a i n e d stable t h r o u g h o u t t h e p e r i o d o f t h e study. M e a n + S D signal levels at e a c h site o f t h e s t o m a c h in b o t h s t u d y g r o u p s a r e s h o w n in Fig. 2. B e c a u s e t h e S t u d e n t ' s t-test r e v e a l e d t h a t is no significant differe n c e b e t w e e n the a n t e r i o r a n d p o s t e r i o r walls at a n y p a r t i c u l a r p o i n t o f t h e
60
i
i
i
~
~
i
L
i
i
i
50
9~
40
~_ 2o ~0
I
3
!
I
I
I
4
5
6
7
points of measurement
Fig. 2. Gastric mucosal blood distribution in control versus cirrhotic rats. * P < 0.05; ** P < 0.001; D, controls; I , cirrhotics
370 stomach, only seven points of measurements are illustrated in Fig. 2. Corpus mucosal blood flow was significantly reduced in cirrhotics compared with controis and the distal stomach had a higher reduction of flow (P = 0.001) in relation to that of the proximal in cirrhotics versus controls (P = 0.05). In contrast to the corpus mucosal blood flow. antral blood flow exhibited a slight, but not statistically significant, increase. The greater curvature, which was highly perfused in controls, had a statistically significant decline in mucosal blood flow, in contrast to the lesser curvature, which - being purely perfused in normal rat exhibited a slight, but not statistically significant, increase in flow in cirrhotics. The highest significant difference in perfusion of all parts of the stomach was observed in the main portion of the anterior and posterior corpus mucosa, which being the highest perfused areas in controls - exhibited a highly statistically significant reduction in flow (34.7%). Discussion Splanchnic hemodynamic response to portal hypertension has been the subject of several recent studies [3, 4, 6, 9, 13]. According to these studies, it is now accepted that systemic circulation becomes hyperdynamic, that is, with increased cardiac output, splanchnic blood flow. and decreased vascular resistance. However, the effect of these hemodvnamic alterations on total and mucosal gastric blood flow is still controversial. The present study, conducted in portal hypertensive rats due to liver cirrhosis, revealed that corpus mucosal blood flow was significantly reduced, while antral mucosal blood flow was only slightly increased. Similar findings were also reported in cirrhotic humans with portal hypertensive gastropathy changes, the gastric mucosal blood flow being measured through the endoscope by use of the laser-Doppler technique [9, 11, 18]. In another clinical study, gastric mucosal hemodynamics were assessed by the use of the hydrogen clearance technique for blood-flow measurement and reflectance spectrophotometry for mucosal blood volume and oxygen saturation measurements: blood flow and oxygen saturation were found to be significantly decreased compared to control subjects, but gastric mucosal blood volume was unaltered [1]. These findings matched in well with the existence of a significantly increased number of open arteriovenous anastomoses, documented, in cirrhotic human stomachs (in the gastric corpus and not in the antrum) with casting techniques by Hashizume [15] as well as with the presence of dilated submucosal precapillaries, capillaries, and veins and straight pattern of arterioles, causing the gastric mucosa to have a mosaic-like appearance [10, 15, 17, 21, 24]. At experimental level, Manabe [20] also demonstrated a striking increase of gastric submucosal arteriovenous shunts in the gastric corpus, leading to the reduction of effective mucosal blood flow, both in portal-vein-ligated and in CC14induced cirrhotic rabbits. Nagamine et al. [22] and Satani et al. [26] also concluded that the decreased mucosal blood flow found in dogs was due to arteriovenous shunting induced by the hyperdynamic state. On the other hand, two other investigators studied gastric mucosal blood flow in a chronic portal hypertension rat model and found it to be increased [5, 25]. Geraghty et al. [13], working on a partially ligated portal vein model, showed by the use of autoradiography that corpus mucosal blood flow was significantly reduced 3 days after portal vein
371 ligation, but this reduction was not sustained at the 7th and 28th days, the level of perfusion being higher on the 28th day. They also found no significant difference of flow in the antral mucosa at any study period. The discrepancy between the results of all these studies could be explained by the differences (1) in the method of.portal hypertension production, (2) in the time of the study after portal hypertension establishment, and (3) in the bloodflow m e a s u r e m e n t technique used [27]. In recent work, Kravetz et al. [19] have documented that findings of studies in prehepatic models of portal hypertension are dissimilar to those in rats with portal hypertension due to cirrhosis of the liver. Our model of CC14-induced cirrhosis is considered to be closer to the clinical situation of the patients with liver cirrhosis, in both histological and functional aspects [12]. Although there is a discrepancy in the degree of portal-systemic shunt development, ranging from 0.2% to 85%, according to different studies [7, 8, 14, 31], this could be due to the different degree of disease evolution and the presence of ascites. In any case, it is evidence that there is a degree of flow increase towards the stomach [12, 19], a redistribution of the blood flow within the gastric wall [13], and a diminished microcirculation on the gastric corpus mucosa, exactly as also occurs in man. This finding in the CC14-induced cirrhotic rat seems to be of great clinical importance, because it appears it could be used as a model for the study of portal hypertensive gastropathy. As there is to date no experimental model of portal hypertensive or congestive gastropathy with a background of liver cirrhosis, further investigation could be planned for the pharmacological manipulation of this complex entity.
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