CALCIUM EFFLUX AND SECRETION OF α-AMYLASE FROM RAT PANCREAS

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Abstract
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.