Relationship between plasma pH and pancreatic HCO3-secretion at different intravenous secretin infusion rates

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Abstract
The relationship between pancreatic HCO3- secretion and plasma pH during acute systemic acid-base changes was investigated in 6 anesthetized, artificially ventilated pigs (20-25 kg) at 2 different, i.v. secretin infusion rates. At 0.45 C.U.[combining unit]/kg b.wt. [body weight] per h secretin infusion and plasma pH 7.40 .+-. 0.01 pancreatic HCO3- secretion averaged 61 .+-. 12 .mu.mol/min. Stepwise lowering of plasma pH through i.v. infusion of HCl and CO2 administration to inspired air proportionately reduced the secretion rate; estimated zero HCO3- secretion occurring at plasma pH 7.01. Subsequent i.v. secretin infusion at 2.70 C.U./kg b.wt. h-1 increased HCO3- secretion to 249 .+-. 42 .mu.mol/min at plasma pH 7.33 + 0.04; stepwise lowering of plasma pH proportionately reduced HCO3- secretion to estimated 0 at plasma pH 6.71. A reduction of plasma pH by 0.1 pH unit reduced HCO3- secretion during low and high rate of i.v. secretin infusion by 18 .+-. 3 .mu.mol/min and 35 .+-. 8 .mu.mol/min, respectively. Secretin infusion rate did not affect pancreatic Cl- excretion. Secretin apparently increases HCO3- secretion and proton transport to the interstitial fluid by augmenting the proton motive force developed by HCO3- secreting cells.

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