Glomerular blood flow after single nephron obstruction in the rat kidney

This study examined the effects of kidney tubule lumen obstruction on glomerular blood flow (GBF) in anesthetized rats. GBF was estimated using microspheres having 9 micron diameter and averaged 239 +/- 10 nl/min in normal nephrons of 41 control rats. Tubule blockade with either paraffin wax or castor oil produced identical results. GBF after 1-2 h of obstruction did not differ from normal. After 1 day, GBF averaged two-thirds of normal, and after 1 wk GBF averaged one-third of normal. The hemodynamic changes produced by obstruction for 1 wk were diminished by chronic administration of high doses of the converting enzyme inhibitor captopril or acute administration of the angiotensin antagonist saralasin. The results suggest that angiotensin contributes to the vasoconstriction produced by prolonged obstruction. Nephrons blocked with castor oil contained oil 1 wk later, had a GBF of 88 +/- 24 nl/min, and were atrophied. We conclude that chronic single nephron obstruction produces progressive vasoconstriction, that this response is in part angiotensin mediated, and that the end result is nephron atrophy.