Role of nitric oxide in desmopressin-induced vasodilation of microperfused rabbit afferent arterioles.

We have previously reported that desmopressin (dDAVP) increased the lumen diameter of norepinephrine (NE)-constricted isolated microperfused rabbit afferent arterioles. In this study, we examined the role of nitric oxide in dDAVP-induced vasodilation of afferent arterioles. We microdissected a superficial afferent arteriole from the kidney of a New Zealand white rabbit. Each afferent arteriole was cannulated with a pipette system and microperfused in vitro at 60 mmHg. dDAVP increased the lumen diameter of NE-preconstricted rabbit afferent arterioles dose-dependently. dDAVP-induced vasodilation was abolished by pretreatment with NG-nitro-L-arginine (L-NNA, 10(-4)M) (L-NNA + NE, 6.7 +/- 1.1 microns; L-NNA + NE + dDAVP, 7.3 +/- 1.4 microns, n = 8). dDAVP increased the lumen diameter of NE-preconstricted afferent arterioles pretreated with L-NNA and L-arginine (10(-2)M) (L-NNA + L-arginine + NE, 6.1 +/- 1.1 microns; L-NNA + L-arginine + NE + dDAVP, 8.7 +/- 0.9 microns*; *p < 0.05, n = 6). Aspirin-DL-lysine (10(-4)M) did not influence dDAVP-induced afferent arteriolar vasodilation (aspirin + NE, 6.4 +/- 0.8 microns; aspirin + NE + dDAVP, 9.6 +/- 1.3 microns *; *p < 0.05, n = 5). These results suggest that nitric oxide may be responsible for dDAVP-induced afferent arteriolar vasodilation.