Mechanism of impaired water excretion in acute right ventricular failure in conscious dogs.

Considerable controversy exists as to what extent left atrial receptors play a role in the physiological regulation of antidiuretic hormone (ADH) secretion.We studied conscious dogs during a stable water diuresis induced by continuous infusion of hypotonic saline, in whom acute inflation of a chronically implanted pulmonary artery balloon consistently produced antidiuresis.Following balloon inflation in nine dogs, glomerular filtration rate (GFR) (67 ± 8 to 70 ± 6 ml/min,P < 0.2) and osmolar clearance (C Osm ) (3.1 ± 0.2 to 3.3 + 0.2 ml/min,/> > 0.2) did not change.Despite a fall in plasma osmolality (287 ± 6 to 281 ± 5 mOsm/kg H 2 O,P < 0.025) and rise in mean systemic arterial pressure (100 ± 3.6 to 110 ± 3.8 mm Hg,P < 0.01), urine osmolality rose markedly (88 ± 8 to 234 ± 45 mOsm/kg H 2 O, P < 0.02), and urine flow ( 10.1 ± 0.8 to 6.3 ± 0.9 ml/min, P < 0.01) and renal free water clearance (C Hl0 ) (7.1 ± 0.8 to 2.9 ± 0.7 ml/min, P < 0.01) both fell.This acute decrease in water excretion was shown to be the consequence of a rise in plasma levels of ADH (0.72 ± 0.07 to 2.06 ± 0.20 /iU/ml) which returned toward control levels following balloon deflation (1.14 ± 0.18 /iU7ml).The changes in ADH levels were shown to be associated with reciprocal changes in left atrial pressure (10.7 ± 1.7 to 6.1 ± 1.5 mm Hg after balloon inflation, returning to 12.2 ± 1.8 mm Hg after deflation).We conclude that in conscious dogs the effects of a small fall in left atrial pressure can predominate over the combined effects of a rise in systemic arterial pressure, continued infusion of hypotonic saline, and a fall in plasma osmolality, to produce a rise in plasma levels of ADH and antidiuresis.