Europ.J.clin.Invest. 5, 401-408 (1975)
The Effect of Propranolol and Phentolamine on Serum Gastrin Concentration in Response to Respiratory Acidosis in No& Man H. Kaesst, G. Utz, U. Teckentrup, A.M. Hauck, and M. Darner Department of Internal Medicine, University of Heidelberg, Germany Received: September 12, 1974, and in revised form: January 28, 1975
Abstract. Serum gastrin concentration and basal acid secretion were studied in normal subjects under the influence of respiratory acidosis induced by C02 rebreathing. During the intragastric instillation of 100 ml/h 0.5 M bicarbonate a significant increase of gastrinaemia from 130 to 158 pg/ml (p < 0.01) occurred in ten subjects during respiratory acidosis (pC02 62 torr, pH 7.25). Under. the intragastric instillation of 100 ml/h 0.1 N HCl the rise of gastrin concentration in response to C02 rebreathing (pC02 68 torr, pH 7.20) was not significant. The relationship between the decrease of pH and the increase of the gastrin concentration was shifted in the direction of a greater systemic acidosis compared to the results performed in the presence of a neutral intragastric pH. 50 pg/kg propranolol intravenously produced a decrease of gastrin concentrations from 145 to 127 pg/ml (p < 0.01) and a total suppression of hypergastrinaemia in respons'e to C02 rebreathing, suggesting activation of beta-cell receptors in respiratory acidosis. The infusion of phentolamine in a dose of 0.6 to 1.8 mg/min. resulted in a rise of gastrin concentration from 140 to 165 pg/ml (p c 0.01) which was not further elevated during respiratory acidosis. The basal acid secretion showed a significant rise in response to C02 rebreathing, which was abolished by the administration of propranolol.
Key words: Gastrin, respiratory acidosis, propranolol, phentolamine, acid secretion
Recently it has been speculated that gastrin release and gastric secretion induced by central nervous stimulation are related to cholinergic and adrenergic impulses ( 1 - 4). Hayes e t al. (5) described hypergastrinaemia in two subjects with pheochromocytoma, which dropped to normal concentrations following the exstirpation of the tumour. A rise of gastrin concentration was observed in dog and man during the administration of epinephrine ( 5 , 6). Stadil and Rehfeld (6) reported, that the rise of gastrin concentration after exogenous administration of epinephrine was suppressed by pretreatment with a beta-adrenergic blocking agent. On the other side, the hypergastrinaemia in two subjects with pheochromocytoma was abolished by phenoxybenzamine, suggesting a stimulatory alpha-adrenergic action on the release of gastrin (5). Indirect and direct evidence indicate, that in respiratary and metabolic acidosis the plasma concentrations of norepinephrine and epinephrine are elevated in relationship to the degree of the derangement of the acid-base state (7, 8). Therefore, studies on gastrinaemia were performed during respiratory acidosis induced by C02 rebreathing in normal subjects. Furthermore, the effect of blockade of alpha-cell receptors with phentolamine and of beta-cell receptors with propranolol
A' preliminary report has been given at the 8th Ann. Meeting of the European Society for Clinical Investigation, Rotterdam 1974
was studied to characterize the mechanism by which catecholamines affect the gastrin concentration.
Methods 35 healthy male volunteers, aged 20 - 33 years (average 26) were studied. After an overnight fast the subjects were put on a bed and a slow infusion of 0.9 X NaCl into an antecubital vein was started to allow the collection of venous blood. A nasogastric tube was placed at the fundic region of the stomach in the experiments performed with the intragastric instillation of bicarbonate and hydrochloric acid. In the experiments for the investigation of the gastric juice the position of the naso-gastric tube in the distal antrum was checked by radioscopy. For the intragastric instillation of bicarbonate and HC1 an infusion pump (Braun, Melsungen, Typ 1850) was used. After a control period of 75 - 105 min., C02 rebreathing was started in order to induce respiratory acidosis. For this purpose the test person was connected with a closed circuit-spirometer system. The system contained approximately 128 1 at the beginning and was filled with more than 95 X oxygen (rest nitrogen) to prevent hypoxia during the rebreathing period. The oxygen concentration in the inspired air never went below 75 X during the whole rebreathing period. C02 rebreathing was stopped when pC02 had reached 60 torr. A subsequent observation period of 60 min. finished the experiment.
H. Kaess et a l . : Effect of Propranolol and Phentolamine
4 02
The period of rebreathing was 32 min. on average (range 17 - 45 min.). Under the administration of phentolamine, this period was significantly reduced to 15 min. (range 10 20 min.) while propranolol had no effect (average 34 min., range 22 - 45 min.) . Samples of peripheral venous blood and capillary blood for blood gas analysis were taken before the introduction of the naso-gastric tube, at regular intervals during the control period, at intervals of 2 - 10 min. during the C02 rebreathing period and at 15, 30, and 60 min. during the subsequent observation period. Concomitantly to the collection of blood samples pulse rate and arterial pressure were recorded. Blood to determine pB and pC02 was collected from an ear lobe which was "arterialized" by inducing local hyperaemia with cutaneous application of Finalgon 10 min. prior to the collection. This method was found sufficiently reliable by Ulmer et a t . (9) as well as in our own preliminary tests in comparison with arterial samples when the determination was performed immediately after the collection of the specimen. The serum of venous samples was stored at -15OC until assayed for glucose, free fatty acids and gastrin. Propranolol (DocitonR, Rheinpharma) , a betablocking substance was diluted in 10 r n l saline and injected intravenously in 3 min. Phentolamine (RegitinR, Ciba) , an alpha-blocking substance was infused intravenously by means of an infusion pump (Braun, Melsungen, Typ B 70202) in a solution of 1 mg/ml during the last 30 min. of the control period, during the C02 rebreathing period and the subsequent observation period. Six types of experiments were performed, 1 . in 10 subjects the investigation was done during intragastric instillation of 0.5 M NaHCO3. After a loading dose of 50 ml, 100 ml/h were infused during the whole experiment. 2 . In the Same 10 subjects the bicarbonate solution was replaced by 0.1 N Hc1. 3 . 50 pg/kg propranolol were given 10 min. before starting the C02 rebreathing period in 10 subjects. 4. Phentolamine in a dose of 0.6 1.8 mg/min. was infused intravenously in 8 subjects. The dosage of phentolamine was adjusted to an acceleration of the pulse rate of 10 - 20 beats/min. over the control period. In the series performed under the effect of propranolol and phentolamine ( 3 and 4 ) the subjects received an intragastric instillation of 0.5 M bicarbonate as described above. 5. In 9 subjects the gastric juice was collected in 15 min. fractions during a control period of 75 min. and during a period of 90 min. after starting the C02 rebreathing period. 6. Ten subjects, in whom the gastric secretion was studied in the same manner as in series 5 , received 50 pg/kg propranolol 10 min. before the C02 rebreathing period.
-
-
Most subjects complained about some discomfort such as headache at the end of the C02 rebreathi n g period. Side effects after propranolol were
not revealed. Following phentolamine nasal congestion was observed. Serum gastrin concentration was determined by radioimmunoassay as described previously (10). The coefficient of variation calculated from triplicate determinations of a control serum (96 pg/ml) was 12 ;b in 3 different assays and 4.8 a to 8.4 % within the assays. The concentration of glucose in the serum was examined with the glucose-oxidase method (Boehringer, Mannheim) and the concentration of free fatty acids was measured by titration using an autoanalyzer after extraction following the method of Dole ( 1 1 ) . The blood gas analysis was carried out for pH and pC02 with a microelectrode (Eschweiler, Kiel). The volume of each fraction of gastric juice was recorded. The acid concentration was determined by titration with 0.1 N NaOH to pH 7.0 using the autotitrator PTT 2 Radiometer, Copenhagen. The paired T test was used to test differences between the serum concentrations of glucose, free fatty acids, pC02, pH in the control and the C02 rebreathing period. For the statistical analysis of differences in gastrin concentration the Friedman test (%*) was employed?. For the relation between the gastrin concentration and pH a linear regression was calculated as well as the correlation coefficient. Mean values are given with the standard error of the mean (SEM).
ResuZts Under the intragastric instillation of bicarbonate, a significant increase of pC02 from 42 to 62 torr (p < 0.01) and a significant decrease of pH from 7.43 to 7.25 (p < 0.01) associated with a significant increase of gastrinaemia from 130 to 158 pg/ml (p < 0.01) occurred in response to C02 rebreathing (Fig. 1 ) . In the subsequent observation period gastrinaemia decreased slowly, while pC02 and pH reached normal values within 15 min. During the intragastric acidification with 0.1 N HC1 a greater acidosis was obtained in response to C02 rebreathing as indicated by the decrease of pH from 7.39 to 7.20 (Fig. 2 ) . The rise of the gastrin concentration was diminished to between 132 and 152 (p > 0.05). In five of the ten subjects an increase of gastrinaemia of more than 15 pg/ml occurred at the end of the rebreathing period, whereas in the other persons a smaller increase or a decrease was observed. Pretreatment with propranolol resulted in a decrease of the gastrin concentration in the control period (Fig. 3 ) . The first value of the C02 rebreathing period was significantly lowered. During the C02 rebreathing period the gastrin concentration remained unchanged. During the administration of phentolamine gastrinaemia rose significantly from 142 to 165 'The contribution of Professor H. Immich, Institute for Documentation and Statistics Heidelberg to these calculations is gratefully recognized.
H. Kaess e t az.: Effect of Propranolol and Phentolamine
I-
50ml 0.5 M NaHC03
7.4
30- 1
7.2 20-
-;
. -
The Effect of Propranolol and Phentolamine on Serum Gastrin Concentration in Response to Respiratory Acidosis in No& Man H. Kaesst, G. Utz, U. Teckentrup, A.M. Hauck, and M. Darner Department of Internal Medicine, University of Heidelberg, Germany Received: September 12, 1974, and in revised form: January 28, 1975
Abstract. Serum gastrin concentration and basal acid secretion were studied in normal subjects under the influence of respiratory acidosis induced by C02 rebreathing. During the intragastric instillation of 100 ml/h 0.5 M bicarbonate a significant increase of gastrinaemia from 130 to 158 pg/ml (p < 0.01) occurred in ten subjects during respiratory acidosis (pC02 62 torr, pH 7.25). Under. the intragastric instillation of 100 ml/h 0.1 N HCl the rise of gastrin concentration in response to C02 rebreathing (pC02 68 torr, pH 7.20) was not significant. The relationship between the decrease of pH and the increase of the gastrin concentration was shifted in the direction of a greater systemic acidosis compared to the results performed in the presence of a neutral intragastric pH. 50 pg/kg propranolol intravenously produced a decrease of gastrin concentrations from 145 to 127 pg/ml (p < 0.01) and a total suppression of hypergastrinaemia in respons'e to C02 rebreathing, suggesting activation of beta-cell receptors in respiratory acidosis. The infusion of phentolamine in a dose of 0.6 to 1.8 mg/min. resulted in a rise of gastrin concentration from 140 to 165 pg/ml (p c 0.01) which was not further elevated during respiratory acidosis. The basal acid secretion showed a significant rise in response to C02 rebreathing, which was abolished by the administration of propranolol.
Key words: Gastrin, respiratory acidosis, propranolol, phentolamine, acid secretion
Recently it has been speculated that gastrin release and gastric secretion induced by central nervous stimulation are related to cholinergic and adrenergic impulses ( 1 - 4). Hayes e t al. (5) described hypergastrinaemia in two subjects with pheochromocytoma, which dropped to normal concentrations following the exstirpation of the tumour. A rise of gastrin concentration was observed in dog and man during the administration of epinephrine ( 5 , 6). Stadil and Rehfeld (6) reported, that the rise of gastrin concentration after exogenous administration of epinephrine was suppressed by pretreatment with a beta-adrenergic blocking agent. On the other side, the hypergastrinaemia in two subjects with pheochromocytoma was abolished by phenoxybenzamine, suggesting a stimulatory alpha-adrenergic action on the release of gastrin (5). Indirect and direct evidence indicate, that in respiratary and metabolic acidosis the plasma concentrations of norepinephrine and epinephrine are elevated in relationship to the degree of the derangement of the acid-base state (7, 8). Therefore, studies on gastrinaemia were performed during respiratory acidosis induced by C02 rebreathing in normal subjects. Furthermore, the effect of blockade of alpha-cell receptors with phentolamine and of beta-cell receptors with propranolol
A' preliminary report has been given at the 8th Ann. Meeting of the European Society for Clinical Investigation, Rotterdam 1974
was studied to characterize the mechanism by which catecholamines affect the gastrin concentration.
Methods 35 healthy male volunteers, aged 20 - 33 years (average 26) were studied. After an overnight fast the subjects were put on a bed and a slow infusion of 0.9 X NaCl into an antecubital vein was started to allow the collection of venous blood. A nasogastric tube was placed at the fundic region of the stomach in the experiments performed with the intragastric instillation of bicarbonate and hydrochloric acid. In the experiments for the investigation of the gastric juice the position of the naso-gastric tube in the distal antrum was checked by radioscopy. For the intragastric instillation of bicarbonate and HC1 an infusion pump (Braun, Melsungen, Typ 1850) was used. After a control period of 75 - 105 min., C02 rebreathing was started in order to induce respiratory acidosis. For this purpose the test person was connected with a closed circuit-spirometer system. The system contained approximately 128 1 at the beginning and was filled with more than 95 X oxygen (rest nitrogen) to prevent hypoxia during the rebreathing period. The oxygen concentration in the inspired air never went below 75 X during the whole rebreathing period. C02 rebreathing was stopped when pC02 had reached 60 torr. A subsequent observation period of 60 min. finished the experiment.
H. Kaess et a l . : Effect of Propranolol and Phentolamine
4 02
The period of rebreathing was 32 min. on average (range 17 - 45 min.). Under the administration of phentolamine, this period was significantly reduced to 15 min. (range 10 20 min.) while propranolol had no effect (average 34 min., range 22 - 45 min.) . Samples of peripheral venous blood and capillary blood for blood gas analysis were taken before the introduction of the naso-gastric tube, at regular intervals during the control period, at intervals of 2 - 10 min. during the C02 rebreathing period and at 15, 30, and 60 min. during the subsequent observation period. Concomitantly to the collection of blood samples pulse rate and arterial pressure were recorded. Blood to determine pB and pC02 was collected from an ear lobe which was "arterialized" by inducing local hyperaemia with cutaneous application of Finalgon 10 min. prior to the collection. This method was found sufficiently reliable by Ulmer et a t . (9) as well as in our own preliminary tests in comparison with arterial samples when the determination was performed immediately after the collection of the specimen. The serum of venous samples was stored at -15OC until assayed for glucose, free fatty acids and gastrin. Propranolol (DocitonR, Rheinpharma) , a betablocking substance was diluted in 10 r n l saline and injected intravenously in 3 min. Phentolamine (RegitinR, Ciba) , an alpha-blocking substance was infused intravenously by means of an infusion pump (Braun, Melsungen, Typ B 70202) in a solution of 1 mg/ml during the last 30 min. of the control period, during the C02 rebreathing period and the subsequent observation period. Six types of experiments were performed, 1 . in 10 subjects the investigation was done during intragastric instillation of 0.5 M NaHCO3. After a loading dose of 50 ml, 100 ml/h were infused during the whole experiment. 2 . In the Same 10 subjects the bicarbonate solution was replaced by 0.1 N Hc1. 3 . 50 pg/kg propranolol were given 10 min. before starting the C02 rebreathing period in 10 subjects. 4. Phentolamine in a dose of 0.6 1.8 mg/min. was infused intravenously in 8 subjects. The dosage of phentolamine was adjusted to an acceleration of the pulse rate of 10 - 20 beats/min. over the control period. In the series performed under the effect of propranolol and phentolamine ( 3 and 4 ) the subjects received an intragastric instillation of 0.5 M bicarbonate as described above. 5. In 9 subjects the gastric juice was collected in 15 min. fractions during a control period of 75 min. and during a period of 90 min. after starting the C02 rebreathing period. 6. Ten subjects, in whom the gastric secretion was studied in the same manner as in series 5 , received 50 pg/kg propranolol 10 min. before the C02 rebreathing period.
-
-
Most subjects complained about some discomfort such as headache at the end of the C02 rebreathi n g period. Side effects after propranolol were
not revealed. Following phentolamine nasal congestion was observed. Serum gastrin concentration was determined by radioimmunoassay as described previously (10). The coefficient of variation calculated from triplicate determinations of a control serum (96 pg/ml) was 12 ;b in 3 different assays and 4.8 a to 8.4 % within the assays. The concentration of glucose in the serum was examined with the glucose-oxidase method (Boehringer, Mannheim) and the concentration of free fatty acids was measured by titration using an autoanalyzer after extraction following the method of Dole ( 1 1 ) . The blood gas analysis was carried out for pH and pC02 with a microelectrode (Eschweiler, Kiel). The volume of each fraction of gastric juice was recorded. The acid concentration was determined by titration with 0.1 N NaOH to pH 7.0 using the autotitrator PTT 2 Radiometer, Copenhagen. The paired T test was used to test differences between the serum concentrations of glucose, free fatty acids, pC02, pH in the control and the C02 rebreathing period. For the statistical analysis of differences in gastrin concentration the Friedman test (%*) was employed?. For the relation between the gastrin concentration and pH a linear regression was calculated as well as the correlation coefficient. Mean values are given with the standard error of the mean (SEM).
ResuZts Under the intragastric instillation of bicarbonate, a significant increase of pC02 from 42 to 62 torr (p < 0.01) and a significant decrease of pH from 7.43 to 7.25 (p < 0.01) associated with a significant increase of gastrinaemia from 130 to 158 pg/ml (p < 0.01) occurred in response to C02 rebreathing (Fig. 1 ) . In the subsequent observation period gastrinaemia decreased slowly, while pC02 and pH reached normal values within 15 min. During the intragastric acidification with 0.1 N HC1 a greater acidosis was obtained in response to C02 rebreathing as indicated by the decrease of pH from 7.39 to 7.20 (Fig. 2 ) . The rise of the gastrin concentration was diminished to between 132 and 152 (p > 0.05). In five of the ten subjects an increase of gastrinaemia of more than 15 pg/ml occurred at the end of the rebreathing period, whereas in the other persons a smaller increase or a decrease was observed. Pretreatment with propranolol resulted in a decrease of the gastrin concentration in the control period (Fig. 3 ) . The first value of the C02 rebreathing period was significantly lowered. During the C02 rebreathing period the gastrin concentration remained unchanged. During the administration of phentolamine gastrinaemia rose significantly from 142 to 165 'The contribution of Professor H. Immich, Institute for Documentation and Statistics Heidelberg to these calculations is gratefully recognized.
H. Kaess e t az.: Effect of Propranolol and Phentolamine
I-
50ml 0.5 M NaHC03
7.4
30- 1
7.2 20-
-;
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