AUTHOR=Huang Xiaohua , Hamza Shereen M. , Zhuang Wenqing , Cupples William A. , Braam Branko 

TITLE=Angiotensin II and the Renal Hemodynamic Response to an Isolated Increased Renal Venous Pressure in Rats

JOURNAL=Frontiers in Physiology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.753355

DOI=10.3389/fphys.2021.753355

ISSN=1664-042X

ABSTRACT=Elevated central venous pressure increases renal venous pressure (RVP) which can affect kidney function. We previously demonstrated that increased RVP reduces renal blood flow (RBF), glomerular filtration rate (GFR) and renal vascular conductance (RVC). We now investigated whether the RAS and RBF autoregulation are involved in the renal hemodynamic response to increased RVP. ANG II levels were clamped by infusion of ANG II after administration of an ACE inhibitor in male Lewis rats. This did not prevent the decrease in ipsilateral RBF (-1.9±0.4ml/min, P<0.05) and GFR (-0.77±0.18 ml/min, P<0.05) upon increased RVP, however, it prevented the reduction in RVC entirely. Systemically, the RVP induced decline in MAP was more pronounced in ANG II clamped animals versus controls (-22.4±4.1 vs. -9.9±2.3mmHg, P<0.05) whereas the decreases in heart rate (HR) was slightly less (-23±4 bpm vs -5±6 bpm, P<0.05). In animals given vasopressin to maintain a comparable MAP after ACE inhibition, increased RVP did not impact MAP and HR. RVC also did not change (0.018±0.008 ml/min.mmHg) and the reduction of GFR was no longer significant (-0.54±0.15 ml/min). Furthermore, RBF autoregulation remained intact and was reset to a lower level when RVP was increased. In conclusion, RVP-induced renal vasoconstriction is attenuated when ANG II is clamped or inhibited. The systemic effect of increased RVP, a decrease in heart rate related to a mild decrease in blood pressure, is attenuated also during ANG II clamp. Last, RBF autoregulation remains intact when RVP is elevated and is reduced to lower levels of renal blood flow. This suggests that in venous congestion, the intact RBF autoregulation could be partially responsible for the vasoconstriction.