Increases in cellular sodium concentration by arginine vasopressin and endothelin in cultured rat glomerular mesangial cells

The present study was undertaken to determine whether arginine vasopressin (AVP), angiotensin-II, and endothelin (ET) increase the cellular sodium concentration ([Na+]i) in cultured rat glomerular mesangial cells. [Na+]i was measured using the fluorescence indicator dye sodium-binding benzofuran isophthalate. These three vasoconstrictor hormones increased cellular free calcium ([Ca2+]i) and [Na+]i in a dose-dependent manner ([Na+]i: basal, 11.5; 10(-7) M AVP, 20.5; 10(-7) M angiotensin-II, 13.8; and 10(-7) M ET, 21.2 mM). The mobilization of [Ca2+]i was faster than that of [Na+]i. The AVP-induced increase in [Na+]i was completely blunted by the potent V1 antagonist d(CH2)5Tyr(Me)AVP. Vasoconstrictor hormones produced a biphasic cellular pH (pHi) change, characterized by a transient acidification, followed by a sustained alkalinization. The Ca(2+)-free condition markedly reduced AVP- and ET-induced increases in [Ca2+]i and [Na+]i and biphasic changes in pHi. In the Na(+)-free state, the hormonally mobilize...