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

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Abstract
Considerable controversy exists as to what extent left atrial receptors play a role in the physiological regulation of antidiuretic hormone (ADH) secretion. Conscious dogs were studied 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 9 dogs, glomerular filtration rate (GFR) (67 .+-. 8 to 70 .+-. 6 ml/min, P < 0.2) and osmolar clearnace (COsm) (3.1 .+-. 0.2 to 3.3 + 0.2 ml/min, P > 0.2) did not change. Despite a fall in plasma osmolality (287 .+-. 6 to 281 .+-. 5 mosmol/kg H2O, 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 mosmol/kg H2O, 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 (CH2O) (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 .mu.U/ml) which returned toward control levels following balloon deflation (1.14 .+-. 0.18 .mu.U/ml). 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). 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.