Tubuloglomerular feedback-mediated decreases in glomerular pressure in Munich-Wistar rats

Publisher Website
Google Scholar
Abstract
Glomerular capillary pressure and single nephron glomerular filtration rate (SNGFR) tubuloglomerular feedback responses were evaluated in Munich-Wistar rats during increased distal flow rate achieved by infusing an isotonic electrolyte solution into unblocked late proximal tubules. Arterial pressure averaged 114 .+-. 2 mmHg and proximal tubule pressure was 14 .+-. 1 mmHg. In 8 tubules, control SNGFR based on distal tubular fluid collections averaged 22 .+-. 3 nl/min, decreased to 15 .+-. 2.3 nl/min when 10-12 nl/min of perfusate was infused into the late proximal tubule and further decreased to 9 .+-. 1.7 nl/min at an infusion of 20-24 nl/min. In 22 tubules, control glomerular capillary pressure was 55 .+-. 1.6 mmHg, decreased to 43 .+-. 2.5 mmHg with addition of perfusate into a late proximal tubule at a rate of 24 nl/min and returned to 53 .+-. 3.1 mmHg when perfusion was stopped. In 8 nephrons, glomerular capillary pressure was shown to be responsive to smaller increments in the late proximal infusion rate and was reduced by 4 .+-. 0.5 and 7 .+-. 1.1 mmHg at the intermediate rates of 10 and 15 nl/min, respectively. Glomerular pressure decreases during increased distal delivery even when the tubule is not blocked. The hypothesis that increases in afferent arteriolar resistance are primarily responsible for feedback-mediated reductions in GFR was supported.