Responses of renal hemodynamics and function to acute volume expansion in the conscious dog

The renal vascular and functional responses to acute volume expansion were determined in conscious dogs with all reflexes intact, sinoaortic arterial baroreceptor denervation, arterial baroreceptor denervation plus bilateral stellectomy, and arterial baroreceptor denervation plus bilateral vagotomy. In the intact dogs, when an isotonic saline infusion increased right atrial pressure by 6 mm Hg, arterial pressure increased by 15 +/- 3 from 95 +/- 3 mm Hg (P less than 0.01) and heart rate rose from 87 +/- 4 to 135 +/- 6 beats/min (P less than 0.01), while renal blood flow rose only slightly (4 +/- 2%), and calculated renal resistance was not altered significantly. After arterial baroreceptor denervation, volume expansion with saline induced a greater rise in blood flow (16 +/- 2%), but did not alter arterial pressure, and calculated resistance fell by 19 +/- 3% from 0.72 +/- 0.05 mm Hg/ml per min (P less than 0.01), while heart rate still increased. After arterial baroreceptor denervation and either bilateral stellectomy or vagotomy, volume expansion reduced renal vascular resistance by similar amounts. When intact animals were volume expanded by 20% of estimated blood volume with isooncotic, isotonic 3% dextran in saline solution, and with renal perfusion pressure held constant, central venous pressure increased by 4.5 +/- 0.6 from 1.8 +/- 0.4 mm Hg (P less than 0.01), renal blood flow increased significantly by 16 +/- 5 ml/min (P less than 0.05) from 191 +/- 30 ml/min, while calculated renal vascular resistance decreased significantly by 0.08 +/- 0.02 from 0.62 +/- 0.09 mm Hg/ml per min (P less than 0.05). Average urine flow rate and sodium excretion 10-60 minutes after expansion increased markedly by 1.85 +/- 0.27 ml/min and 9.84 +/- 1.13 muEq/min per kg, respectively (P less than 0.01). After arterial baroreceptor denervation, volume expansion induced a similar rise in central venous pressure and renal blood flow. The diuretic and natriuretic responses were not attenuated by arterial baroreceptor denervation. After arterial baroreceptor denervation plus bilateral vagotomy, there was a significant and similar rise in renal blood flow, whereas diuretic (urine flow rate rose by only 0.50 +/- 0.10 from 0.35 +/- 0.08 ml/min) and natriuretic (sodium excretion rose by only 4.83 +/- 0.95 from 1.50 +/- 0.48 muEq/min per kg) responses were significantly attenuated (P less than 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)