The effect of AVP-V-2 receptor stimulation on local GFR in the rat kidney

The effect of AVP-V-2 receptor agonist desmopressin, dDAVP, its non-peptide antagonist OPC-31260 and vehicle infusion on glomerular filtration rate (G FR) in the outer, middle and inner cortex was studied in both hydropenic an d water diuretic Inactin anaesthetized female Sprague-Dawley rats using the aprotinin method. Two subsequent GFR measurements were carried our in the same kidney by injection of I-125- and I-131-labelled aprotinin before and after i.v. infusion of dDAVP. OPC-31260 or the vehicle. Acute infusion of d DAVP in hydropenic rats increased total GFR by 14% relative to vehicle infu sion, whereas in water diuretic rats it had no effect relative to vehicle. No significant changes in arterial pressure (P-a) or renal blood flow (RBF) were recorded. infusion of OPC-31260 reduced total GFR by 11% compared wit h vehicle. These results are consistent with the findings that a presensiti zation of the vasculature by high plasma levels of AVP is necessary for the renal vascular effects mediated by the V-2 or V-2-like receptors to occur. The ratio between inner and outer cortex GFR remained unchanged from contr ol to experimental condition as follows: dDAVP infusion in hydropenic rats, 0.504 vs. 0.494 in control, vehicle infusion in hydropenic rats, 0.393 vs. 0.392; OPC-31260 infusion in hydropenic rats, 0.517 vs. 0.523. dDAVP in wa ter diuretic rats, 0.547 vs. 0.543; vehicle in water diuretic rats, 0.413 v s. 0.417. Thus no significant difference in the GFR response was observed b etween superficial and deep cortical layers of the rat kidney.