Calyculin A, a phosphoprotein phosphatase inhibitor, stimulates acid secretion in isolated gastric glands

Calyculin A (CLA) stimulates acid secretion in isolated rabbit gastric glands without affecting their adenosine 3',5'-cyclic monophosphate contents. CLA-stimulated secretion is due to an increase in the phosphorylation of protein kinase A substrates, such as ezrin, through the inhibition of protein phosphatase (PrPase) type 1. The inhibition of protein kinase A suppresses the acid secretion. CLA and okadaic acid (OKA) are potent inhibitors of PrPase, but OKA does not stimulate acid secretion.