Renal vascular reactivity to AVP in wild type and CD38 ^‐/‐ mice: modulation by nitric oxide, prostanoids, and superoxide (692.9)

Renal vascular responses to AVP were tested in anesthetized wild‐type (WT) and CD38‐/‐ mice that lack the calcium mobilizing second messenger cyclic ADP ribose. Iv injections of AVP (3‐25ng) produced a dose‐dependent decrease in renal blood flow with a minimum of 25±2% below control in WT and 27±2% in CD38‐/‐ mice at the 25ng dose. Renal vascular resistance (RVR) increased by 75±6% in WT and 78±6% in CD38‐/‐ mice. Inhibition of NO synthase with L‐NAME increased the maximum RVR response to AVP from 71±7 to 308±76% in WT and from 86±7 to 388±81% in CD38‐/‐. Cyclooxygenase inhibition with indomethacin increased the maximum RVR response to 125±15% in WT and 120±14% in CD38‐/‐ mice (P<0.001, <0.05). Superoxide suppression with tempol inhibited the maximum RVR response to AVP by 38% in both strains (p<0.005). All vascular responses to AVP were abolished by an AVP V1a receptor antagonist. Thus, vasoconstriction by AVP in the mouse is caused by V1a receptor activation with no concomitant vasodilatation by V2 receptors. However, renal vasoconstrictor responses to AVP are strongly buffered by vasodilatory actions of NO and prostanoids and augmented by the vasoconstrictor actions of superoxide. Unlike AVP, other vasoconstrictor agents show attenuated vasoconstrictor activity in CD38‐/‐ mice which points to a distinct activation mechanism for AVP that appears to be independent of CD38 and its downstream calcium signaling pathway. Grant Funding Source : Supported by HL‐02334