The effects of microfilament disrupting agents on HCl secretion and ultrastructure of piglet gastric oxyntic cells.

A functionally responsive in vitro preparation of piglet gastric mucosa was used to investigate the involvement of microfilaments in the process of HCl secretion by oxyntic cells. A well-ordered array of microfilaments was observed in the short, stubby microvilli on the apical surface of nonsecreting oxyntic cells, as well as ii the longer microvilli of actively secreting cells. Treatment with cytochalasin B (10(-5)-10(-4) M) caused a dose-dependent inhibition of acid secretion and a concomitant gradient of morphologic alteration of oxyntic cells. Associated with slight (approximately 20%) inhibition of secretion was an initial collapse of the canalicular and glandular lumina and appearance of some pleomorphic-shaped microvilli. Maximum inhibition of secretion always produced a complete collapse of the oxyntic cell canalicular and glandular lumina, with a resultant apposition of apical surfaces. Microvilli were no longer readily distinguishable, and microfilaments were severely disorganized. Treatment with cytochalasin B (2-4 X 10(-5) M) before secretagogue stimulation also reduced the ability of the gastric mucosa to secrete acid; oxyntic cells retained the general appearance of nonsecreting cells. The correlation of disruption of microfilaments and the inhibition of acid secretion by cytochalasin B suggests an involvement of microfilaments in both the initiation and maintenance of high levels of acid secretion.