Cyclic nucleotides inhibit Na+/Ca2+ exchange in cultured human mesangial cells.
Na+/Ca2+ exchange contributes to the control of cytosolic free Ca2+ levels ([Ca2+]i) in resting and activated cultured human mesangial cells. We have previously shown that activation of phospholipase C by vasoconstrictors enhances Ca2+ influx upon extracellular Na+ withdrawal. This effect is not mediated by concurrent activation of protein kinase (PK) C, since it occurs even after PKC inhibition, and phorbol esters actually blunt both basal and stimulated Na+/Ca2+ exchange. We now studied the effects of PKA and PKG activation by adenylate/guanylate cyclase stimuli or by permeant analogues of cyclic nucleotides in monolayer cultures loaded with the fluorescent Ca(2+)-sensitive probe, fura-2. The exchanger was inhibited by the stable prostaglandin I2 analogue, iloprost, which is transduced by cAMP (peak [Ca2+]i inhibition by 1 microM iloprost 35 +/- 3%). Similarly, non-receptor activation of adenylate cyclase by 10 microM forskolin inhibited basal and agonist-stimulated Na+/Ca2+ exchange by 52 +/- 4 and 66 +/- 4%, respectively. Dibutyryl-cAMP (0.1 mM) also inhibited stimulated Na(+)-dependent Ca2+ influx by 72 +/- 2%. The particulate guanylate cyclase agonist, atriopeptin III, and the soluble guanylate cyclase activator, glyceryltrinitrate, also inhibited both basal and angiotensin II-stimulated Na+Ca2+ exchange (to a maximum of 53 +/- 5 and 62 +/- 3%, respectively). Dibutyryl-cGMP (1 mM) mimicked the effects of cGMP stimuli, reducing stimulated Na+/Ca2+ exchange by 79 +/- 2%. Therefore, similar to PKC, cyclic nucleotide activation of PKA and PKG regulates Na+/Ca2+ exchange, providing a functional link between transmembrane signalling systems for vasoactive agents in cultured human mesangial cells.
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Chair of Nephrology, University of Rome La Sapienza, Italy.
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D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology; D005920:Glomerular Mesangium / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D016285:Iloprost / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D009712:Nucleotides, Cyclic / Q000494:pharmacology*; D009994:Osmolar Concentration; D019831:Sodium-Calcium Exchanger
D002352:Carrier Proteins; D009712:Nucleotides, Cyclic; D019831:Sodium-Calcium Exchanger; D000804:Angiotensin II; D000242:Cyclic AMP; D016285:Iloprost; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine