Extent and modulation of junctional communication between pancreatic acinar cells in vivo.

To assess whether junctional communication may be of physiological relevance in the control of exocrine pancreas secretion, we have studied acinar cell coupling by microinjecting Lucifer Yellow CH in the intact pancreas of anesthetized rats. Reconstructions from serial sections showed that, under control conditions, pancreatic cells are extensively coupled within each acinus but do not communicate with centroacinar cells, duct cells, and cells of neighboring acini. Intravenous infusion of acetylcholine and caerulein, or electrical stimulation of the vagus nerve, increased pancreatic secretion (P less than 0.02-0.001). Under these stimulatory conditions, the extent of acinar cell communication was decreased (P less than 0.001) by 40%. The acetylcholine-induced uncoupling was prevented by treating rats with atropine. Thus, in the intact pancreas, acinar cells intercommunicate extensively within each acinus under resting conditions and reduce their coupling during stimulation. These data support the view that modulation of cell coupling is a physiologically relevant mechanism for the regulation of exocrine pancreas secretion in vivo.