Effect of Secretin on Bile Formation in Sheep

Abstract

The rate of flow of bile increased rapidly when pure natural secretin was infused into the portal vein of conscious, standing sheep. The increment in flow was related significantly to the logarithm of the rate of administration but was not affected by the simultaneous infusion of sodium taurocholate into the portal vein. When secretin and taurocholate were given together the rate of flow of bile was five times that during the control period of bile salt deprivation. Secretin stimulated the secretion of total fatty acids into the bile of sheep when they were deprived of recirculated bile salts and also when they received an infusion of taurocholate into the portal vein. The mean maximum rate of total fatty acid secretion was 38 per cent higher during infusion of secretin with taurocholate than during infusion of taurocholate alone. When taurocholate was infused into the portal vein at 37 ,umole/min or less, it was transferred quantitatively into the bile, and secretin did not appear to affect this process. However, when taurocholate was infused alone at 112 ,umole/min it was not transferred quantitatively into the bile, but the efficiency of this transfer was increased by the simultaneous infusion of secretin. The concentration in the bile of total fatty acids and of bile salts decreased during infusion of secretin, but no significant changes occurred in the concentration of sodium. The infusion of secretin caused no significant changes in the osmolality of the bile in five sheep, but in three experiments on a sixth sheep it caused a highly significant increase in osmolality. When secretin was infused into the portal vein, no changes occurred in the arterial pressure, pulse rate, portal venous pressure or respiratory rate. These experiments indicate that secretin could play a significant role in regulating bile secretion in the sheep.Secretin may be an important stimulus to the secretion of water and electrolytes into the bile in carnivorous and omnivorous animals [Still, McBean and

Regulation of Output of Electrolytes in Bile and Pancreatic Juice in Sheep

“…4). The flow of bile, and the output of sodium, potassium, chloride, and bicarbonate increased during the infusion of secretin (P < O• 05-0•001), but when the results were examined by analysis of variance (see Heath 1970), it was not possible to demonstrate any significant interactions between the responses to secretin and those to taurocholate. The flow and electrolyte content of pancreatic juice increased during infusions of secretin, but this response was not altered by the simultaneous infusion of taurocholate.…”

“…Analyses of variance and Student's t•tests were used to evaluate the statistical significance of changes that occurred in the various parameters during the experiments (see Heath 1970).…”

“…No detailed information has been published on the regulation of the output of electrolytes in bile and pancreatic juice in sheep. Although secretin may stimulate secretion of bile (Heath 1970) and pancreatic juice (Magee 1961), the effects of pure natural secretin on the entry of water and electrolytes into the sheep gut have not been recorded. In the experiments reported here, pure natural secretin was infused into the portal vein or the jugular vein of conscious, standing sheep, and measurements were made of the flow and electrolyte content of bile and of pancreatic juice.…”

Effect of Electrical Stimulation of the Vagus Nerves on Bile Secretion in Anaesthetized Sheep

“…However, this occurred only at one level of stimulation, and was observed only in the four sheep used in the first experiment; no significant effect occurred in the four sheep used in the second experiment (Table 1). Furthermore, the increase that was observed ;was small when compared with the effect of exogenous or endogenoll8secretion (Heath 1970;Caple and Heath 1972), and would seem tobeoflittle physiological significance. The results of the second and third experiments did not indicate a role for the vagus nerves in determining either the hepatic response to secretin or the maximum rate of transport of bile salts by the liver.…”

“…In sheep, the rate of flow of bile is considerably higher than in dogs, and both bile salts and secretin appear to playa significant role in the regulation of bile formation (Heath 1970;Heath et al 1970;Caple 1972;Caple and Heath 1972). Although the rate of transport of bile salts by liver cells is an important regulator of bile secretion in sheep, the capacity of these transport mechanisms is limited .…”