Nephrogenous cyclic AMP during extracellular volume expansion: relationship to early and late aortic constriction.

Prior data showed that both volume expansion (ECVE) and renal vasodilatation are associated with natriuresis and increased nephrogenous cAMP (NcAMP). Studies were done to examine the effect of ECVE on sodium excretion and NcAMP during early or late reduction in renal perfusion pressure (RPP) in an effort to define the role of renal vasodilatation on NcAMP during ECVE. In 8 thyroparathyroidectomized (TPTX) dogs, RPP to the left kidney was reduced (130 +/- 1.7 to 69 +/- 4 mm Hg), ECVE was then produced and finally RPP was allowed to rise to 126 +/- 2.2 mm Hg (group I). In 8 TPTX, ECVE was produced and then followed by a reduction in RPP (121 +/- 5 to 69 +/- 5 mm Hg; group II). cAMP was measured in aorta, renal veins and urine. In group I, renal plasma flow (RPF), fractional excretion of Na filtered (FeNa), urinary NcAMP (UNcAMP) and renal vein NcAMP (RVNcAMP) did not change in the constricted kidney while these parameters increased in the other kidney. After release of the constriction RPF (122 +/- 24 to 157 +/- 26 ml/min), FeNa (0.5 +/- 0.1 to 5 +/- 1.2%), UNcAMP (204 +/- 121 to 785 +/- 198 pmol/min, p less than 0.05) and RVNcAMP (277 +/- 213 to 1,565 +/- 403 pmol/min, p less than 0.02) rose significantly. In group II, FeNa, UNcAMP and RVNcAMP increased during ECVE and remained significantly elevated during the reduction in RPP.(ABSTRACT TRUNCATED AT 250 WORDS)