Intraepithelial current flow in rat pancreatic secretory epithelia

Abstract

To assess the importance for transepithelial salt secretion of current flow across the baso-lateral membrane, we studied the effects of ouabain (1 mmol/l), Ba (3 mmol/l) and tetraethylammonium (TEA: 10 mmol/l) on secretion by the acinar (caerulein stimulated) and ductal (secretin stimulated) epithelia of the perfused rat pancreas. Within 10 min, ouabain caused a 79% inhibition of acinar secretion which was resolvable into two exponentials with half-times, respectively, of 0.24 min±0.19 (S.D.) and 6.40±0.46 min. In contrast, it caused only a monoexponential inhibition of ductal secretion (61% in 10 min) with a half-time of 5.08±0.26 min. Ba caused a monoexponential inhibition of acinar secretion (70% in 10 min) with a half-time of 1.82±0.27 min, but it had no inhibitory effect on ductal secretion. The action of TEA was similar to that of Ba: it caused monoexponential inhibition of acinar secretion (26% in 10 min) with a half-time of 1.82±0.03 min, and it too had no effect on ductal secretion. For comparison, we also studied the effect of these drugs on the more rapidly secreting rat mandibular gland (stimulated with acetylcholine). All three drugs were strongly inhibitory: within 10 min, ouabain caused a 95%, Ba an 89% and TEA an 83% inhibition. The decay curves appeared to be monoexponential with halftimes, respectively, of 1.49±0.12, 0.51±0.3 and 0.56±0.02 min. The results support the hypothesis that current flow across the baso-lateral membrane is an important concomitant of secretion by the pancreatic acinar epithelium and by mandibular glands, but they suggest that such a current is not important for secretion by pancreatic ducts.