Micropuncture study of pancreatic secretion in the cat.

Using micropuncture techniques, pancreatic electrolyte secretion was studied in 50 female mongrel cats. During maximal secretin stimulation (GIH, 4 to 6 U per kg-hr), juice was collected from intralobular (10 to 50 mu diameter), and extralobular (25 to 300 mu diameter) ducts by micropuncture and compared with juice simultaneously collected from the main duct. The juice [Cl-] steadily decreased from intralobular ducts (112 +/- 9 mEq per liter) to the main duct (46 +/- 8 mEq per liter). During in vivo perfusion, secretion of H2O and HCO3- by the extralobular ducts (25 to 150 mu diameter) was sensitive to secretin. There was no evidence for secretion by the main duct. Pancreatic secretion of water and electrolytes appears to result from the admixture of a Cl-rich primary secretion originating from intralobular structures and a larger volume of HCO3- -rich fluid originating from the smaller extralobular ducts. HCO3- cl- exchange in these ducts accounts for the characteristic changes in concentrations of HCO3- and Cl- as the flow rate varies.