USE OF PERTUSSIS TOXIN TO INVESTIGATE THE MECHANISM OF ACTION OF PROSTAGLANDIN-F2-ALPHA ON THE CORPUS-LUTEUM IN SHEEP

Pertussis toxin catalysed the ADP-ribosylation of a protein of M(r) 40 000 in ovine luteal tissue. Ribosylation of 45% of this protein in whole cell incubations (as judged by subsequent ribosylation of cell-free preparations in the presence of [P-32]NAD) attenuated the prostaglandin (PG)F2alpha-stimulated hydrolysis of [H-3]inositol-labelled phosphatidylinositol-4,5-bisphosphate into inositol trisphosphate by 60%, but did not affect the inhibition by PGF2alpha of LH-stimulated accumulation of cyclic AMP. It is concluded that activation of phospholipase C by PGF2alpha involves a pertussis toxin-sensitive protein, probably a G protein, and, that the inhibitory effect of PGF2alpha on LH-stimulated adenylate cyclase is unlikely to be directly mediated by such a protein.