Extracellular ATP stimulates polyphosphoinositide hydrolysis and prostaglandin synthesis in rat renal mesangial cells: Involvement of a pertussis toxin-sensitive guanine nucleotide binding protein and feedback inhibition by protein kinase C

Abstract

ATP stimulated a rapid and dose-dependent formation of inositol polyphosphates in rat glomerular mesangial cells. In parallel there was a 80% increase in 1, 2-diacylglycerol (DAG) after 15 s upon stimulation with ATP. The rank order of potency of a series of ATP and ADP analogoues for stimulation of inositol trisphosphate (InsP 3) formation was ATP > ATPγS > βγ-methylene-ATP > βγ-imido-ATP > ADP, while ADPβs, AMP, adenosine and GTP were inactive, indicating the presence of P 2y-purinergic receptors. ATP also stimulated a marked synthesis of prostaglandin E 2 (PGE2). The reank order of potency of different ATP and ADP analogues was identical to that of InsP 3 generation. Pre-treatment of the cells with pertussis toxin strongly attenuated ATP-induced formation of InsP 3 and DAG. Short-term (10 min) pre-treatment of the cells with 12- O-tetradecanoylphorbol 13-acetate (TPA), a potent activator of protein kinase C, produced a dose-dependent inhibition of the ATP-stimulated InsP 3 generation. Furthermore, inhibition of protein kinase C by the potent inhibito staurosporin, or downregulation of protein Kinase C by longterm (24 h) incubation of the cells with TPA, resulted in an enhanced formation of InsP 3 towards a stimulation with ATP.