PANCREATIC INTERSTITIAL PH REGULATION - EFFECTS OF SECRETORY STIMULATION

Background. Bicarbonate secretion by pancreatic ducts presumably relea ses an equivalent amount of acid into the parenchyma. The purpose of t his study was to determine the effects of this acid load on pancreatic interstitial pH (pH(I)). In addition, we examined the relationship of pH(I) to changes in pancreatic blood flow (PBF), which may be importa nt in acid disposal. Methods. After validation of a microelectrode met hod for measurement of pH(I) in anesthetized cats, the effects of secr etin (2 IU/kg intravenously) and cholecystokinin (0.08 mu g/kg intrave nously) were examined. PBF was measured simultaneously by the H-2 gas clearance technique. Results. Secretory stimulation with secretin prod uced an increase in pancreatic bicarbonate secretion (146 +/- 23 mu Eq /15 minutes, p < 0.01). This secretion was associated with a fall in p H(I) from 7.36 +/- 0.02 to 7.31 +/- 0.02 (p < 0.001), which returned t o baseline after 25 minutes. There was an accompanying increase in PBF from 118 +/- 32 to 148 +/- 35 ml/min/100 gm (p < 0.01). In contrast, stimulation with cholecystokinin only slightly increased pancreatic se cretion (49 +/- 19 mu l/15 minutes) and had no significant effects on pH or blood flow. Conclusions. These results suggest that pancreatic s ecretion of bicarbonate, but not protein, releases H+ into the interst itium, an acid tide comparable to the alkaline tide during acid secret ion by the stomach. This interstitial acidosis was accompanied by an i ncrease in PBF. The increase in blood flow may be important in pH home ostasis, contributing to the disposal of this acid.