Hernodynamic Effects of Calibrated Stenosis of the Superior Mesenteric Artery in Conscious Rats with Portal Vein Stenosis OLrVIER SOUBRANE:,
ALAINBRAILI~ON. HAN-CHIEII LIN, GEHHAFtD'T KLEBER AND DIDIERLEBREC
Laboratorre d 'Hemod,vnamrqiie Splarich ti rque, Utirte de Recherclies de Physiopathologie Hepatrque (INSERM U-24),Hbpital Reaulon, 921 18 ('/ichv, France
Because superior mesenteric arterial blood flow is increased in portal hypertension and plays a role in elevated portal pressure, mechanical reduction of artery diameter should induce decreases in portal pressure and superior mesenteric arterial blood flow. In this study, calibrated superior mesenteric artery stenosis (induced with a 22-gauge needle) was performed in rats simultaneously with portal vein stenosis or 2 wk after creation of portal vein stenosis. Hemody namic studies were performed 3 wk after induction of portal vein stenosis in conscious, unrestrained rats. At that time, neither weight loss nor digestive tract alterations were observed in rats with arterial stenosis. In neither group of rats with arterial stenosis was portal tributary blood flow significantly different from that of normal rats; nor was it significantly lower than in rats with portal vein stenosis without arterial stenosis. In both groups of rats with arterial stenosis, portal pressure was significantly lower (12.1 1.6 mm Hg and 12.5 -C 1.8 mm Hg, respectively) than in rats subjected to portal vein stenosis (15.4 1.5 mm Hg) but significantly higher than in controls (7.2 f 1.0 m m Hg). In rats with arterial stenosis, cardiac index was also significantly lower than that in rats with portal vein stenosis but higher than that in controls. In conclusion, this study shows that both early and late superior mesenteric artery stenosis significantlyreduce the degree of portal hypertension and the hyperkinetic state of rats with extrahepatic portal hypertension. Thus we can speculate that superior mesenteric artery stenosis might provide a new therapeutic approach for portal hypertension. (HEPATOLOGY 1992;16:1447-1451).
* *
Because portal hypertension IS partly a result of elevated portal tributary blood flow (1. 2 ) . reduction of
Keceived January 29, 1992. accepted July 20. 1992. 'rhiti work was presented in part at the 4 l s t Annual Meeting nfthe American Association for the Study of Liver Diseases i n ('himgo, Novrrntwr 3-6. 1990. and published in abstract form tH~Psrol.ix:v 1990.12:854~ 0. Soubrane and G. Kleber held fellowships from the Fondatlon piiur la Kecherche M6dicale; H.C. Lin was supported b? the French government. the Veterans General Hospital-Taipei, and National Sciencc (:ouncil. Taiwan. R.0.C' Address reprint requests to. Dr D I r h r w . INSERM Ii24. Hnpitel Rraujnn Clichy, France. 31/1/41321
this circulation should induce a decrease in portal pressure (PP; mm Hg). Most vasoconstrictive substances increase the vascular resistance of various splanchnic organs and thus reduce both portal tributary blood flow (PTBF) and PP (3-5).Theoretically these vasoconstrictive effects can be mechanically induced by reducing the diameter of the superior mesenteric artery (SMA).Because the diameter of this artery is enlarged in portal hypertension, reduction of its caliber should decrease both PTBF flow and PP. The aim of this study was to evaluate the hernodynamic effects of limitation or reduction of SMA diameter in conscious rats with extrahepatic portal hypertension.
MATERIAL AND METHODS Animals. Thirty-three adult male Sprague-Dawley rats I Charles River, Saint-Aubin-les-Elbeuf, France) were divided into four groups. Three groups had portal hypertension induced by portal vein stenosis and one underwent sham surgery ( n = 8). Of the three groups of rats with portal vein stenosis, two had calibrated stenosis of the SMA (seebelow) created concomitantly with portal vein stenosis (n = 8; early stenosis) or 2 wk after induction of portal vein stenosis (n = 7; late stenosis). The third group had only portal vein stenosis = 10). Portal vein stenosis was induced in anesthetized rats weighng 160 to 200 gm as described previously (6). A polyethylene catheter (0.96mm external diameter) was passed along the portal vein, and 3-0 silk was used to ligate both the catheter and the portal vein. The catheter was then removed. Calibrated superior mesenteric stenosis was induced while rats were under ether anesthesia. Median laparotomy was performed, and then the SMA was subjected to stenosis under light microscopy. The first part of the SMA was exposed from the right side of the mesentery, and a 22-gauge needle was placed alongside the artery. Accordingly, the diameter of the SMA was approximately 0.7 mm. A section of 4-0 silk was tied firmly around both the needle and the SMA. The needle was then immediately withdrawn, leaving a stenotic artery. When stenosis of the SMA was performed during surgery to create portal vein stenosis, the diameter of the ligature was the same as that of the artery. This procedure prevented the enlargement of the diameter of the SMA that occurs in portal hypertension. When this procedure was performed 2 wk after portal vein stenosis, SMA stenosis was obtained. In two rats, after hemodynamic measurements were obtained, SMA
In
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SOUBRANE ET AL.
HEPATOLOGY
TABLE 1. Splanchnic hernodynamic values in rats subjected to portal vein stenosis with or without stenosis of the SMA Portal vein and superior mesenteric artery stenosis Sham-operated
Portal vein stenosis
Early (n = 8)
Late
Parameters
(n = 8)
PP (mm Hg) PTBF ( m l * m i n - ' . 100 g m - ' ) Portal territory vascular resistance (dyn*sec.cm-' x l o 3 . 100 g m - ' )
7.2 t 1.0" 5.1 t 1.5 163 ? 16
15.4 t 1.5' 8.8 t 1.7' 90 2 6"
12.1 * 1.6'*' 6.0 ? 1.3' 121 t 7
12.4 5 1.7'8' 6.5 ? 1.0' 106 ? l@
Hepatocollateral vascular resistance
123 2 48
151
2
32
164 t 27
157 ? 49
87
2
' 6
60 2 28'
72 2 10'
(dyn.sec.cm-' x lo3.100 g m - ' ) Mesenteric systemic shunting (%Id
< 0.5
(n
=
10)
(n = 7)
~~
"Results are mean 2 S.D. 'Significantly different from those in sham-operated rats. 'Significantly different from rats with portal vein stenosis without SMA stenosis. dMeasured in four rats of each group.
pressure was measured in each side of the stenosis. This measurement was obtained, while rats were under ether anesthesia, with a 0.3-mm external diameter sharpened catheter, which was inserted into a small ileal artery under light microscopy. In these two rats, both pressures in SMA were similar to aortic pressure. Arterial stenosis was verified in all rats at autopsy after hemodynamic measurements were taken (see below). Preliminary studies showed that all rats that underwent SMA stenosis with a needle smaller than 22 gauge experienced diarrhea and intestinal necrosis and died within a few days of surgery. Protocols used in this laboratory were approved by the French Agricultural Office in conformity with European legislation for research involving animals. Hemadynumic Studies. Three weeks after induction of portal vein stenosis, three catheters were placed in fasted rats while they were under light ether anesthesia. Through a midline laparotomy, an ileal vein was isolated and a 4-cm Silastic catheter (Dow Corning, Midland, MI) was inserted. The tip of the catheter was gently placed in the distal part of the superior mesenteric vein. Then a polyethylene catheter of 0.7 mm external diameter (PE-10 catheter; Biotrol Pharma, Paris, France) was introduced into the lumen of the aorta through the left femoral artery. After neck incision, a 4.3-cm Silastic catheter was introduced into the right common carotid artery and gently advanced up to the left ventricle. Correct ventricular position was verified by monitoring of ventricular pressures and verified at necropsy. The catheters were tunneled toward the back of the neck, and the incisions were closed with catgut. Animals were allowed to recover for 4 hr before hernodynamic measurements, which were taken from conscious and unrestrained rats resting quietly in their cages, were made. Radioactive microspheres were used to determine cardiac output (CO) and organ blood flows (7). Aortic and portal catheters were connected to a pressure monitor for measurements of heart rate, mean arterial pressure (MAP; mm Hg) and PP. Microspheres labeled with l13Sn (16 1 km diameter, specific activity = 10 mCi/gm, DuPont-New England Nuclear, Boston, MA) were suspended in 10%dextran and sonicated for 10 min before injection. A precounted aliquot of 0.2 ml containing approximately 60,000 microspheres was injected into the left ventricle and flushed with 0.5 ml over 30 sec. Starting 5 sec before the microsphere injection, the reference blood sample was withdrawn from the femoral artery catheter into a motor-driven syringe at a rate of 1 mumin for 1 min.
*
Immediately after hemodynamic measurements were taken, the mesenteric component of portal-systemic shunts was quantified in four rats from each group (8). 141Ce-labeled microspheres were injected and flushed with 0.4 ml saline solution into the portal venous system through the superior mesenteric vein catheter over 20 sec. The animals were then killed with pentobarbital, and individual organs were dissected. Radioactivity in each organ and the reference blood sample was counted in a gamma scintillation counter (Compteur Gamma 4000; Intertechnique, Plaisir, France). Hemdynamic Calculutiom. CO was calculated with the following formula: CO (ml/min) = (Radioactivity injected [cpm])/Reference sample radioactivity (cpm) x ' 1 (mumin). Cardiac index (CZ)was derived with the following formula: CI ( m l . m i n - * *100 g m - ' ) = CO/100 gm. Regional blood flow was calculated according to the following formula: Organ blood flow (ml min- 100 gm-') = (Organ radioactivity [cpm])/Radioactivity injected [cpm]) x CI. PTBF was taken as the sum of spleen, stomach, intestine, colon, mesentery and pancreas blood flows. SMA blood flow was taken as the sum of intestine, mesentery (with pancreas) and ascending colon blood flows. Blood flow from portal territories other than the SMA was taken as the sum of spleen, stomach and descending colon blood flows. Systemic vascular resistance (SVR) was calculated according to the following formula: SVR ( d y n . s e c . ~ m - ~ * l OgOn - ' x lo3) = (MAP x BO)/CI. Central venous pressure was not taken because it is known to be 0 mm Hg in rats. Portal tributary vascular resistance fPTVR)was calculated as follows: PTVR (dyn sec . cm-5 * 100 gm- x lo3) = (MAP - PP x 80)PTBF. Superior mesenteric vascular resistance was calculated as the sum of the parallel resistances in the intestines, mesentery (with pancreas) and ascending colon. These organ vascular resistances were calculated as follows: Organ vascular resistance (dyn * sec * cm-5 x lo3) = ([MAP - PPI x 80)/Organ blood flow. Because pressure beyond the arterial stenosis may slightly differ from that before the stenosis, the calculated superior mesenteric vascular resistance might be lower than that reported in this article (see below). Vascular resistance from blood flow from portal territories other than the SMA was calculated as the sum of parallel resistances of the spleen, stomach and descending colon. Hepatocollateral vascular resistance (HCR) was calculated as follows: HCR ( d y n . ~ e c . c m - 100 ~ * g n - ' x lo3) = (PP x 80)PTBF. The degree of mesenteric-systemic shunting (MSS) was calculated with the following formula: MSS (%) = (Lung
-
1449
SI'PEI
ALAINBRAILI~ON. HAN-CHIEII LIN, GEHHAFtD'T KLEBER AND DIDIERLEBREC
Laboratorre d 'Hemod,vnamrqiie Splarich ti rque, Utirte de Recherclies de Physiopathologie Hepatrque (INSERM U-24),Hbpital Reaulon, 921 18 ('/ichv, France
Because superior mesenteric arterial blood flow is increased in portal hypertension and plays a role in elevated portal pressure, mechanical reduction of artery diameter should induce decreases in portal pressure and superior mesenteric arterial blood flow. In this study, calibrated superior mesenteric artery stenosis (induced with a 22-gauge needle) was performed in rats simultaneously with portal vein stenosis or 2 wk after creation of portal vein stenosis. Hemody namic studies were performed 3 wk after induction of portal vein stenosis in conscious, unrestrained rats. At that time, neither weight loss nor digestive tract alterations were observed in rats with arterial stenosis. In neither group of rats with arterial stenosis was portal tributary blood flow significantly different from that of normal rats; nor was it significantly lower than in rats with portal vein stenosis without arterial stenosis. In both groups of rats with arterial stenosis, portal pressure was significantly lower (12.1 1.6 mm Hg and 12.5 -C 1.8 mm Hg, respectively) than in rats subjected to portal vein stenosis (15.4 1.5 mm Hg) but significantly higher than in controls (7.2 f 1.0 m m Hg). In rats with arterial stenosis, cardiac index was also significantly lower than that in rats with portal vein stenosis but higher than that in controls. In conclusion, this study shows that both early and late superior mesenteric artery stenosis significantlyreduce the degree of portal hypertension and the hyperkinetic state of rats with extrahepatic portal hypertension. Thus we can speculate that superior mesenteric artery stenosis might provide a new therapeutic approach for portal hypertension. (HEPATOLOGY 1992;16:1447-1451).
* *
Because portal hypertension IS partly a result of elevated portal tributary blood flow (1. 2 ) . reduction of
Keceived January 29, 1992. accepted July 20. 1992. 'rhiti work was presented in part at the 4 l s t Annual Meeting nfthe American Association for the Study of Liver Diseases i n ('himgo, Novrrntwr 3-6. 1990. and published in abstract form tH~Psrol.ix:v 1990.12:854~ 0. Soubrane and G. Kleber held fellowships from the Fondatlon piiur la Kecherche M6dicale; H.C. Lin was supported b? the French government. the Veterans General Hospital-Taipei, and National Sciencc (:ouncil. Taiwan. R.0.C' Address reprint requests to. Dr D I r h r w . INSERM Ii24. Hnpitel Rraujnn Clichy, France. 31/1/41321
this circulation should induce a decrease in portal pressure (PP; mm Hg). Most vasoconstrictive substances increase the vascular resistance of various splanchnic organs and thus reduce both portal tributary blood flow (PTBF) and PP (3-5).Theoretically these vasoconstrictive effects can be mechanically induced by reducing the diameter of the superior mesenteric artery (SMA).Because the diameter of this artery is enlarged in portal hypertension, reduction of its caliber should decrease both PTBF flow and PP. The aim of this study was to evaluate the hernodynamic effects of limitation or reduction of SMA diameter in conscious rats with extrahepatic portal hypertension.
MATERIAL AND METHODS Animals. Thirty-three adult male Sprague-Dawley rats I Charles River, Saint-Aubin-les-Elbeuf, France) were divided into four groups. Three groups had portal hypertension induced by portal vein stenosis and one underwent sham surgery ( n = 8). Of the three groups of rats with portal vein stenosis, two had calibrated stenosis of the SMA (seebelow) created concomitantly with portal vein stenosis (n = 8; early stenosis) or 2 wk after induction of portal vein stenosis (n = 7; late stenosis). The third group had only portal vein stenosis = 10). Portal vein stenosis was induced in anesthetized rats weighng 160 to 200 gm as described previously (6). A polyethylene catheter (0.96mm external diameter) was passed along the portal vein, and 3-0 silk was used to ligate both the catheter and the portal vein. The catheter was then removed. Calibrated superior mesenteric stenosis was induced while rats were under ether anesthesia. Median laparotomy was performed, and then the SMA was subjected to stenosis under light microscopy. The first part of the SMA was exposed from the right side of the mesentery, and a 22-gauge needle was placed alongside the artery. Accordingly, the diameter of the SMA was approximately 0.7 mm. A section of 4-0 silk was tied firmly around both the needle and the SMA. The needle was then immediately withdrawn, leaving a stenotic artery. When stenosis of the SMA was performed during surgery to create portal vein stenosis, the diameter of the ligature was the same as that of the artery. This procedure prevented the enlargement of the diameter of the SMA that occurs in portal hypertension. When this procedure was performed 2 wk after portal vein stenosis, SMA stenosis was obtained. In two rats, after hemodynamic measurements were obtained, SMA
In
1447
1448
SOUBRANE ET AL.
HEPATOLOGY
TABLE 1. Splanchnic hernodynamic values in rats subjected to portal vein stenosis with or without stenosis of the SMA Portal vein and superior mesenteric artery stenosis Sham-operated
Portal vein stenosis
Early (n = 8)
Late
Parameters
(n = 8)
PP (mm Hg) PTBF ( m l * m i n - ' . 100 g m - ' ) Portal territory vascular resistance (dyn*sec.cm-' x l o 3 . 100 g m - ' )
7.2 t 1.0" 5.1 t 1.5 163 ? 16
15.4 t 1.5' 8.8 t 1.7' 90 2 6"
12.1 * 1.6'*' 6.0 ? 1.3' 121 t 7
12.4 5 1.7'8' 6.5 ? 1.0' 106 ? l@
Hepatocollateral vascular resistance
123 2 48
151
2
32
164 t 27
157 ? 49
87
2
' 6
60 2 28'
72 2 10'
(dyn.sec.cm-' x lo3.100 g m - ' ) Mesenteric systemic shunting (%Id
< 0.5
(n
=
10)
(n = 7)
~~
"Results are mean 2 S.D. 'Significantly different from those in sham-operated rats. 'Significantly different from rats with portal vein stenosis without SMA stenosis. dMeasured in four rats of each group.
pressure was measured in each side of the stenosis. This measurement was obtained, while rats were under ether anesthesia, with a 0.3-mm external diameter sharpened catheter, which was inserted into a small ileal artery under light microscopy. In these two rats, both pressures in SMA were similar to aortic pressure. Arterial stenosis was verified in all rats at autopsy after hemodynamic measurements were taken (see below). Preliminary studies showed that all rats that underwent SMA stenosis with a needle smaller than 22 gauge experienced diarrhea and intestinal necrosis and died within a few days of surgery. Protocols used in this laboratory were approved by the French Agricultural Office in conformity with European legislation for research involving animals. Hemadynumic Studies. Three weeks after induction of portal vein stenosis, three catheters were placed in fasted rats while they were under light ether anesthesia. Through a midline laparotomy, an ileal vein was isolated and a 4-cm Silastic catheter (Dow Corning, Midland, MI) was inserted. The tip of the catheter was gently placed in the distal part of the superior mesenteric vein. Then a polyethylene catheter of 0.7 mm external diameter (PE-10 catheter; Biotrol Pharma, Paris, France) was introduced into the lumen of the aorta through the left femoral artery. After neck incision, a 4.3-cm Silastic catheter was introduced into the right common carotid artery and gently advanced up to the left ventricle. Correct ventricular position was verified by monitoring of ventricular pressures and verified at necropsy. The catheters were tunneled toward the back of the neck, and the incisions were closed with catgut. Animals were allowed to recover for 4 hr before hernodynamic measurements, which were taken from conscious and unrestrained rats resting quietly in their cages, were made. Radioactive microspheres were used to determine cardiac output (CO) and organ blood flows (7). Aortic and portal catheters were connected to a pressure monitor for measurements of heart rate, mean arterial pressure (MAP; mm Hg) and PP. Microspheres labeled with l13Sn (16 1 km diameter, specific activity = 10 mCi/gm, DuPont-New England Nuclear, Boston, MA) were suspended in 10%dextran and sonicated for 10 min before injection. A precounted aliquot of 0.2 ml containing approximately 60,000 microspheres was injected into the left ventricle and flushed with 0.5 ml over 30 sec. Starting 5 sec before the microsphere injection, the reference blood sample was withdrawn from the femoral artery catheter into a motor-driven syringe at a rate of 1 mumin for 1 min.
*
Immediately after hemodynamic measurements were taken, the mesenteric component of portal-systemic shunts was quantified in four rats from each group (8). 141Ce-labeled microspheres were injected and flushed with 0.4 ml saline solution into the portal venous system through the superior mesenteric vein catheter over 20 sec. The animals were then killed with pentobarbital, and individual organs were dissected. Radioactivity in each organ and the reference blood sample was counted in a gamma scintillation counter (Compteur Gamma 4000; Intertechnique, Plaisir, France). Hemdynamic Calculutiom. CO was calculated with the following formula: CO (ml/min) = (Radioactivity injected [cpm])/Reference sample radioactivity (cpm) x ' 1 (mumin). Cardiac index (CZ)was derived with the following formula: CI ( m l . m i n - * *100 g m - ' ) = CO/100 gm. Regional blood flow was calculated according to the following formula: Organ blood flow (ml min- 100 gm-') = (Organ radioactivity [cpm])/Radioactivity injected [cpm]) x CI. PTBF was taken as the sum of spleen, stomach, intestine, colon, mesentery and pancreas blood flows. SMA blood flow was taken as the sum of intestine, mesentery (with pancreas) and ascending colon blood flows. Blood flow from portal territories other than the SMA was taken as the sum of spleen, stomach and descending colon blood flows. Systemic vascular resistance (SVR) was calculated according to the following formula: SVR ( d y n . s e c . ~ m - ~ * l OgOn - ' x lo3) = (MAP x BO)/CI. Central venous pressure was not taken because it is known to be 0 mm Hg in rats. Portal tributary vascular resistance fPTVR)was calculated as follows: PTVR (dyn sec . cm-5 * 100 gm- x lo3) = (MAP - PP x 80)PTBF. Superior mesenteric vascular resistance was calculated as the sum of the parallel resistances in the intestines, mesentery (with pancreas) and ascending colon. These organ vascular resistances were calculated as follows: Organ vascular resistance (dyn * sec * cm-5 x lo3) = ([MAP - PPI x 80)/Organ blood flow. Because pressure beyond the arterial stenosis may slightly differ from that before the stenosis, the calculated superior mesenteric vascular resistance might be lower than that reported in this article (see below). Vascular resistance from blood flow from portal territories other than the SMA was calculated as the sum of parallel resistances of the spleen, stomach and descending colon. Hepatocollateral vascular resistance (HCR) was calculated as follows: HCR ( d y n . ~ e c . c m - 100 ~ * g n - ' x lo3) = (PP x 80)PTBF. The degree of mesenteric-systemic shunting (MSS) was calculated with the following formula: MSS (%) = (Lung
-
1449
SI'PEI
