Inter-Relationship between Autoregulation of Glomerular Filtration Rate, Tubuloglomerular Feedback and Juxtaglomerular Renin Activity in Normotensive and Hypertensive Rats

1. Reduction of renal perfusion pressure from 133 mmHg to 117 mmHg in control rats did not induce a significant change of kidney glomerular filtration rate (GFR) or nephron GFR determined in distal tubules. In contrast, nephron GFR measured in proximal tubular segments (NGFR-P) fell significantly. 2. Qualitatively the same response of filtration rate to changes of arterial blood pressure was found in the chronically clipped kidneys of Goldblatt hypertensive rats after acute removal of the clip. 3. In contrast, autoregulation of kidney GFR, NGFR-D and NGFR-P was abolished in the contralateral kidneys of Goldblatt hypertensive rats. 4. Microperfusion studies showed that tubuloglomerular feedback regulation of NGFR was present in the renin-rich ischaemic kidneys of Goldblatt rats after removal of the constricting clip, but greatly attenuated in the renin-depleted contralateral kidneys. 5. These data indicate that tubuloglomerular feedback participates in establishing renal autoregulation, possibly by mediation of the renin-angiotensin system.