Renin and Distal Tubule Na During Stop Flow in Dogs

Summary

Using radioimmunoassay techniques, arterial (A) and renal venous (RV) plasma renin activities were measured in sodium pentobarbital-anesthetized dogs during clearance and stop-flow periods. Changes in RV-A renin were used to estimate changes in renin secretion. RV-A renin increased during stop flow from its average value during clearance periods, whether 10% mannitol in 0.15 M NaCl or 10% mannitol in 0.1 M Na₂SO₄ was being administered intravenously. However, RV-A renin during mannitol + NaCl stop-flow periods was significantly greater than during mannitol + Na₂SO₄ stop-flow periods. Distal tubular fluid Na concentrations as indicated by stop-flow analysis were higher during the latter. These observations suggest that a macula densa stimulus, Na concentration, and/or load, may control renin secretion during ureteral occlusion.

This research was supported by National Science Foundation Grant GB 35263 and grants from the Kidney Foundation of Michigan and the Michigan Heart Association.