CALCIUM EFFLUX AND SECRETION OF α‐AMYLASE FROM RAT PANCREAS

1 The efflux of 45Ca from rat pancreas was investigated in relation to the secretion of α‐amylase. 2 The 45Ca space in the pancreas was increased 1.6 times when pancreatic tissue was incubated in media in which the extracellular calcium concentration was reduced from 1.0 to 0.05 Mm. 3 Carbachol increased the rate of 45Ca efflux from the tissue and this effect was associated with an increase in the release of α‐amylase. Dibutyryl cyclic adenosine monophosphate (AMP) also evoked a secretory response, but did not alter the rate of 45Ca efflux. In combination with carbachol, the dibutyryl analogue of cyclic AMP reduced the carbachol‐stimulated increase in 45Ca efflux while enhancing the release of secretory protein. 4 The stimulatory effect of carbachol on 45Ca efflux was observed when pancreatic tissues were incubated in media containing a high concentration of ethyléneglycolbis (β‐aminoethyl)‐N,N′‐tetraacetic acid (EGTA). 5 Atropine blocked the effects of carbachol on both 45Ca efflux and secretion of α‐amylase. 6 It was concluded that intracellular calcium can and may sustain stimulus‐secretion coupling in the rat exocrine pancreas.