"Structural autoregulation" of blood flow and GFR in the two renal vascular beds from two-kidney, one-clip renal hypertensive rats, as compared with kidneys from uni-nephrectomized and intact normotensive rats.

Both kidneys from two-kidney, one-clip renal hypertensive rats (RHR) and the hypertrophied kidney of uni-nephrectomized rats (UNR) were investigated during artificial perfusion with 2% Dextran solution and kerosene at maximal vasodilatation, and studied with respect to organ weight, vascular resistance, preglomerular/postglomerular resistance ratio and glomerular filtration capacity. Paired perfusions were throughout used, isolated kidneys from age-matched normotensive rats serving as controls. The untouched, "high-pressure" RHR kidney had increased 40% in weight/100 g b.w. while its vascular resistance at maximal dilatation had increased almost 60%/g organ weight. Glomerular filtration capacity and preglomerular/postglomerular resistance ratio remained, however, largely unchanged. The clipped "low-pressure", RHR kidney was reduced 40% in weight and 45% in renal vascular resistance/g organ weight. It also showed a reduced pre/postglomerular resistance ratio and some reduction of filtration capacity. The remaining hypertrophied kidney in UNR had increased 40% in weight, while its vascular resistance and filtration capacity/g organ weight, as well as its pre/postglomerular resistance ratio were unchanged. It is concluded that the kidney in renovascular hypertension rapidly adapts structurally not only in tissue mass, but also concerning total vascular resistance and pre/postglomerular resistance ratio, so as to chronically "autoregulate" GFR to match the altered pressure situation. Likewise, after unilateral nephrectomy the remaining, normotensive kidney increases in mass, with matched increases in blood flow and glomerular filtration capacity, while total resistance/g organ weight and the pre/postglomerular resistance ratio remain at normotensive levels.