AUTOREGULATION OF TOTAL AND ZONAL GLOMERULAR-FILTRATION RATE IN SPONTANEOUSLY HYPERTENSIVE RATS WITH MESANGIOLYSIS

In this study we tested the hypothesis that mesangial cells participat e in autoregulation of the glomerular filtration rate (GFR) in normote nsive and hypertensive rats. Mesangial cell lesions were induced by in travenous administration of antithymocyte (anti-Thy 1.1) antibodies in spontaneously hypertensive rats (SHR) and in Wistar-Kyoto rats (WKY). Normal murine serum was injected in control rats. Hemodynamic measure ments were performed 24 h after the infusion of the anti-Thy 1.1 antib odies. Renal blood flow (RBF) was measured by a transit time flowmeter (Transonic) and the GFR was measured as the uptake of (125)iodine-lab eled aprotinin (I-125-Ap) by proximal tubular cells at the control ren al arterial pressure and I-125-Ap at a pressure reduction close to the lower pressure limit of RBF autoregulation. RBF was unaltered and the autoregulatory capability was maintained in SHR and WKY after mesangi al cell lesions. Mesangiolysis significantly reduced the total GFR in normotensive, but not in hypertensive animals. The fractional compensa tion of the GFR was attenuated in the outer cortical layer (p<0.05) in normotensive WKY. In SHRs the fractional compensation of the GFR was impaired in all cortical layers after mesangiolysis, slightly more in the outer than In the inner cortex. We conclude that mesangial cells m ay contribute to the autoregulation of GFR in hypertensive rats, but t o a lesser extent in normotensive rats.