Renal modulation of electrically stimulated adrenal medullary secretion

In acutely anephric dogs, depressed reflex adrenal medullary secretion (AMS) may be related to low plasma angiotensin. Either local (adrenal medulla) or central nervous system mechanisms are responsible. Local influences of acute bilateral nephrectomy on AMS were evaluated after left splanchnic nerve section. Two groups of five healthy, fasted mongrel dogs (16-20 kg) were prepared (Na pentobarbital iv anesthesia, 98% O2/2% CO2, Harvard volume ventilator) at celiotomy with blood pressure and sampling catheters per femoral arteriotomies and left adrenal-femoral venous T-shaped Silastic shunt. Group 2 dogs had acute bilateral nephrectomy. The acutely divided distal left splanchnic nerve was arranged for electrical stimulation (Grass, bipolar nerve stimulator, 1 0 V, 1-msec delay, 10 Hz, 10-msec square wave). Heparin anticoagulation was maintained and arterial pH monitored. Simultaneous adrenal vein, aortic blood sampling, and adrenal blood flow (F) determinations followed 10-min periods of alternating electrical stimulation and nerve rest. AMS for epinephrine (E) and norepinephrine (NE) was calculated [E and NE plasma concentration (single isotope radioenzymatic technique) differences of adrenal vein minus aorta multiplied by F]. Results were grouped, analyzed for variance, and compared (Wilcoxon unpaired rank sum, Student's test, Fischer's tables, ANOVA). Low aortic E, NE concentrations confirmed absent systemic adrenergic stimulation. The AMS ratio of NE:E was low in the anephric group. At the first stimulation interval NE:E was 0.28 +/- 0.14 (1 SD) in renal intact dogs vs 0.11 +/- 0.04 in anephric dogs, P less than 0.05. At rest NE:E was 0.33 +/- 0.12 in group 1 vs 0.17 +/- 0.02 in group 2 dogs, P less than 0.02. Plasma NE was also low in the anephric group (289 mg/liter +/- 126 (1 SD) vs 612 +/- 189, P = 0.033, resting).(ABSTRACT TRUNCATED AT 250 WORDS)