Arginine Vasopressin and Oxytocin Increase Intracellular Calcium and cAMP in Human Glomerular Epithelial Cells in Culture

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Abstract
The signal transduction linkages of arginine vasopressin (AVP) and oxytocin receptors were investigated in human glomerular epithelial cells (GEC) in culture. AVP (ED50, 10-7 mol/l) and oxytoxin (ED50, 3×10-8 mol/l) induced a rapid, transient and dose-dependent increase in [Ca2+]i as detected by fura-2 microfluorimetry. The baseline of [Ca2+]i in human GEC was 109+2.8 nmol/l (n = 60). The Vla receptor antagonist [d(CH2)51, Tyr(Me)2, Arg8]-vasopressin inhibited the AVP-(IC50, 5×10-9mol/l) and oxytocin-induced (IC50, 3×10-8 mol/l) increase in [Ca2+]i in a dose-dependent manner. Both, AVP and oxytocin caused accumulation of cAMP The AVP-stimulated cAMP increase was blocked by pretreatment of human GEC with the Vla receptor antagonist (10-7 mol/l), whereas the oxytocin-induced cAMP accumulation remained uninfluenced. In conclusion the present results indicate that: (1) via Vla receptor activation, AVP and oxytocin induce a transient elevation in [Ca2+]i in human GEC; (2) AVP and oxytocin cause cAMP accumulation; (3) the AVP-induced cAMP accumulation is inhibited by a Vla receptor antagonist, whereas (4) the oxytocin response showed no effect. In addition, a different receptor might be possible, at least in oxytocin-induced-cAMP accumulation.

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