U-73122, an Aminosteroid Phospholipase C Antagonist, Noncompetitively InhibitsThyrotropin-Releasing Hormone Effects in GH sub 3 Rat Pituitary Cells

摘要

TRH increases cytosolic-free calcium (Ca 2 + or -) by activating phospholipaseC(PL-C), which induces phosphoinositol hydrolysis, leading to Ca2+ mobilization from inositol trisphosphate (IP3) sensitive stores, and by increasing Ca2+ influx. Increases in Ca2+, stimulate PRL secretion. We investigated the effects of U-73122, an aminosteroid inhibitor of PL-C dependent processes, on TRH-stimulated second messenger pathways and on PRL secretion in GH3 rat pituitary cells. Ca2+i was monitored by Indo-1 fluorescence, and IP3 and metabolites