Effects of chronic tubular obstruction in Necturus kidney.

The effects of chronic single nephron or mesonephric duct obstruction on renal pressures were measured in anesthetized Necturi by servo-null techniques. Glomerular capillary hydrostatic pressure (PGC) averaged 11.3 +/- 1.2 (SD) cmH2O in 18 normal nephrons. Chronic tubule blockade for 2-6 days produced no significant change in PGC. Light and electron microscopy of the juxtaglomerular apparatus (JGA) revealed juxtaglomerular cell granules widely dispersed along the course of preglomerular arterioles, a deficient macula densa, and no polkissen. The absence of a detectable change in PGC with chronic tubule blockade, i.e., a tubuloglomerular feedback response, may reflect poor development of the JGA in this amphibian.