Renal autoregulation dynamics monitored across the renal surface

Abstract

We extended dynamic analysis of renal autoregulation across a spatial surface using laser speckle perfusion imaging (LSPI) of an area of the renal cortex. Anaesthetized (isoflurane) male Long‐Evans rats (N=8) had left kidneys exposed and an occluder placed around the renal artery. Monitoring included LSPI of the renal cortex, renal blood flow (RBF) and blood pressure (BP) under BP forcing during NOS inhibition by intrarenal infusion of L‐NAME (10 μg/min × 20 min then 3 μg/min i.r.a.) followed by rho‐kinase inhibition by intrarenal infusion of Y‐27632 (to achieve 10 μmol/L in RBF). Transfer function analysis was performed with either RBF or LSPI as output signals and BP as the input. Using both pairs of transfer functions, we found a significant increase in coherence (0.05 – 0.08 Hz) and a significant decrease in gain slope (0.05 – 0.15 Hz) and phase (0.1 Hz) from L‐NAME to Y‐27632. These results indicate LSPI detected decreased tubuloglomerular feedback and myogenic activity during rho‐kinase inhibition. Additionally, using LSPI we were able to identify changes at all locations within the imaging window, and using time‐varying analysis we were able to identify them temporally. We conclude that transfer function analysis of LSPI can be used to monitor renal autoregulation across spatial and temporal dimensions. This work was performed under CIHR Grant MOP‐102694, and CS was supported by an AHA predoctoral fellowship.