Differential glomerular response to continuous infusion of vasopressin in spontaneously hypertensive rats and Wistar-Kyoto rats.

To determine the difference of glomerular response to exogenous vasopressin (VP) in vivo between normotensive and hypertensive rats, we examined the effects of 14-day continuous infusion of VP (1.0 ng/kg/min) on the physiological and histological aspects in 7-week-old spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. VP infusion did not result in significant changes in systolic blood pressure, heart rate, serum electrolytes, serum creatinine, urinary protein and N-acetyl-beta-glucosaminidase levels in both strains of rats. VP infusion significantly reduced daily urine volume associated with significant concentration of the urine in WKY rats but not SHR. Kidney and heart weights did not differ significantly after VP infusion between both strains. Glomerular mesangial expansion was significantly enhanced in VP infused SHR, but glomerular cellularity was not different between both strains following treatment. Competitive reverse transcription-polymerase chain reaction revealed that the level of glomerular transforming growth factor (TGF)-beta1 mRNA was significantly higher in SHR than WKY rats, and that this difference was significantly augmented after VP infusion in SHR. VP infusion, however, did not change the level of glomerular mRNAs of platelet-derived growth factor (PDGF) B-chain in both strains. Then, exogenous VP infusion contributes to the glomerular mesangial expansion in SHR, which involved overexpression of glomerular TGF-beta1 without any pressor effect. In contrast, the significant changes of glomerular expansion and TGF-beta1 level were not shown in WKY rats. These findings suggest that the glomerular response to the exogenous VP is preferentially enhanced in SHR.