Implication of microtubules and microfilaments in the cyclic GMP response of rat exocrine pancreas to secret agogues

Microtubules and microfilaments have been shown to be involved in the secretion processes of many glands: thyroid gland [ 11, pancreatic islets [2], adrenal medulla [3], anterior pituitary [4], parotid gland [ 51 and exocrine pancreas [6,7]. Most of these studies used drugs known to alter the structure of these cellular organelles. On the other hand, microtubules as well as microfilaments have been implicated in the control of the redistribution and motility of membrane surface components [8-l 21. Furthermore, recent studies suggested that microtubules and/or microfilaments are probably involved in the process of adenylate cyclase stimulation by hormones [ 13,141. In pancreatic acinar cells the initial step in the sequence of events mediating the action of secretagogues is an increase in intracellular guanosine 3’:5’ cyclic monophosphate (cyclic GMP) [ 15 ,161. Further, microtubules and microfilaments were shown to be widely distributed in these cells [7]. Thus the present study was undertaken in order to investigate the possible role of microtubules and microfilaments in the secretagogue-induced cyclic GMP accumulation by rat exocrine pancreas. We report that both vinblastine which causes the disappearance of microtubules [ 7,171, and cytochalasin B which impairs the function of microfilaments [7,18] inhibit the cyclic GMP response of rat exocrine pancreas to peptide hormones (caerulein), cholinergic agents (carbachol) or the calcium ionophore A 23 187.