Effect of okadaic acid on hormone- and mastoparan-stimulated phosphoinositide turnover in isolated rat hepatocytes.
Okadaic acid is a potent and specific inhibitor of protein phosphatases 1 and 2A which seems to be useful for identifying biological processes that are controlled by reversible phosphorylation of proteins. We report here that okadaic acid inhibits in isolated hepatocytes the stimulations of phosphoinositide turnover induced by epinephrine, angiotensin II and vasopressin. Mastoparan, a peptide toxin from wasp venom that mimics receptors by activating G-proteins, also stimulates the accumulation of inositol phosphates in hepatocytes. Interestingly, this action of mastoparan was also inhibited by okadaic acid. Our data indicate that okadaic acid inhibits the phosphoinositide turnover signal transduction system in hepatocytes at a level distal to the receptors.
García-Sáinz
J A
JA
Instituto de Fisiología Celular, UNAM, México D. F.
Macías-Silva
M
M
Romero-Avila
M T
MT
D000818:Animals; D002478:Cells, Cultured; D004988:Ethers, Cyclic / Q000494:pharmacology*; D005260:Female; D006728:Hormones / Q000378:metabolism; D007295:Inositol Phosphates / Q000037:antagonists & inhibitors / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D019319:Okadaic Acid; D010455:Peptides; D010716:Phosphatidylinositols / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors*; D051381:Rats; D011919:Rats, Inbred Strains; D015398:Signal Transduction / Q000187:drug effects; D014862:Wasp Venoms / Q000494:pharmacology*
D004988:Ethers, Cyclic; D006728:Hormones; D007295:Inositol Phosphates; D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; D010716:Phosphatidylinositols; D014862:Wasp Venoms; D019319:Okadaic Acid; C037500:mastoparan; D010749:Phosphoprotein Phosphatases