[Current results on the hormonal and autoregulatory control of renal blood flow]

The split hydronephrotic kidney of rats offers for the first time the opportunity to visualising virtually all pre- and postglomerular arterioles by intravital-microscopy. Measurements of blood flow velocity and vessel diameters enable the degree of vasodilation and the blood flow at various loci within the kidney e.g. single glomeruli, to be calculated. Thus, the modulating effects of renal perfusion pressure on renal microcirculation, or local and systemic application of vasoactive substances can be examined. Reduced renal perfusion pressure induces an autoregulatory response, i.e. preglomerular vasodilation and constancy of glomerular blood flow, comparable to that shown by clearance and blood flow measurements in the whole kidney of rats anaesthetised by pentobarbital. Angiotensin II induces a dose dependent vasoconstriction in all pre- and postglomerular vessels with the exception of the renin containing segment of the vas afferens close to the glomerulus. Calcium antagonists effect a preglomerular vasodilation and block renal autoregulation, whereas atrionatriuretic peptide (ANF) dilates preglomerular vessels and leaves autoregulation intact. In conclusion, the non-filtering hydronephrotic kidney is a valuable model, on which to directly observe the effects of alterations in renal perfusion pressure and the effects of hormonal or pharmacologically vasoactive substances controlling renal microcirculation.