Effects of isatin on atrial natriuretic peptide-mediated accumulation of cGMP and guanylyl cyclase activity of PC12 cells

We have previously demonstrated that isatin (indole-2,3 dione), an endogeno us compound widely distributed in mammalian tissues and body fluids, effect ively inhibits atrial natriuretic peptide (ANP) receptor binding and ANP-st imulated guanylyl cyclase activity of rat membrane preparations. In the pre sent study the effects of isatin on ANP-mediated accumulation of cGMP and g uanylyl cyclase (GC) activity of PC12 cells were studied. Isatin (0.1 mM) e ffectively inhibited ANP-stimulated GC-activity of broken cells but was nea rly inactive in attenuating ANP-dependent accumulation of cGMP in intact PC 12 cells. The ATP-analogue adenylylimidodiphopshate (AMP-PNP) slightly pote ntiated the ANP effect on GC activity in broken cell preparations and signi ficantly reduced GC sensitivity to isatin. Isatin caused a more pronounced reduction of ANP-dependent cGMP accumulation in cells grown in the presence of 10% embryonal calf serum (ECS) than in 0.5% ECS. The data obtained sugg est that, in intact cells, the manifestation of the isatin effect on ANP-me diated signal transduction may depend on intracellular factor(s), possibly interacting at the kinase domain. (C) 2001 Elsevier Science Inc. All rights reserved.