AJP - Gastrointestinal and Liver Physiology, Vol 240, Issue 2 130-G140, Copyright © 1981 by American Physiological Society

ARTICLES

Secretagogue-induced changes in subcellular Ca2+ distribution in isolated pancreatic acini

R. L. Dormer and J. A. Williams

In a prior study, we demonstrated that pancreatic secretagogues increased both the uptake into and washout of 45Ca2+ from isolated mouse pancreatic acini. The net result of these processes was an initial fall in total acinar cell Ca2+ content. In the present study, we have employed subcellular fractionation of acini under conditions that minimized posthomogenization redistribution of Ca2+ in order to localize those organelles involved in intracellular Ca2+ fluxes. Homogenization and differential centrifugation of acini, preloaded with 45Ca2+ and subjected to a period of washout, showed that carbachol induced an increased loss of 45Ca2+ from all fractions isolated. The high-speed microsomal fraction lost 45Ca2+ to a greater extent than did whole acini; measurement of total Ca2+ by atomic absorption spectrometry showed a net loss of Ca2+ from this fraction. Purification of the lower-speed fractions indicated that carbachol increased 45Ca2+ exchange with both zymogen granules and mitochondria, but net Ca2+ levels in these organelles were unchanged. It was concluded that stimulation of pancreatic acini by carbachol results in the release of calcium from a microsomal compartment leading to a rise in cytoplasmic Ca2+, increased exchange with granule and mitochondrial Ca2+, and increased efflux of Ca2+ from the cell.

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				D. I. Yule, S. A. Ernst, H. Ohnishi, and R. J.H. Wojcikiewicz Evidence That Zymogen Granules Are Not a Physiologically Relevant Calcium Pool. DEFINING THE DISTRIBUTION OF INOSITOL 1,4,5-TRISPHOSPHATE RECEPTORS IN PANCREATIC ACINAR CELLS J. Biol. Chem., April 4, 1997; 272(14): 9093 - 9098. [Abstract] [Full Text] [PDF]