ALTERED RENAL DOPAMINE-RECEPTORS DURING DEVELOPMENT OF CARDIAC-HYPERTROPHY

The characteristics of dopamine receptors were studied in heart and kidney using the radiolabeled receptor assay of [H-3]spiperone during the development of cardiac hypertrophy. Male Sprague-Dawley rats (175-200 g) underwent abdominal aortic constriction above the renal arteries and were studied 3, 14, and 28 days thereafter. Sham-operated animals without aortic constriction were used as control. Although the ratio of left ventricular weight to total body weight was significantly increased 14 and 28 days after aortic constriction in animals, [H-3]spiperone binding in left ventricular membrane was increased as early as 3 days after aortic constriction. At 14 days, the binding was still elevated and, by 28 days, it returned to control values. In contrast, membranes obtained from kidney cortex showed an elevation of [H-3]spiperone binding only at 28 days after aortic constriction; at 3 days the binding values were decreased. A reciprocal correlation was found between the number of dopamine receptors and the activity of Na+-K+-ATPase at 28 days of aortic constriction; the enzyme activity, as measured by the release of P-32(i) from [gamma-P-32]ATP, was decreased in kidney cortex. Autoradiographic data also showed an increased number of dopamine receptors in kidney at 28 days after abdominal aortic constriction. These results suggest that the dopamine receptor is increased very early in heart in response to pressure overload as a result of a compensatory response to maintain an optimal left ventricular output. Kidney dopamine receptors are triggered at a later stage possibly to maintain fluid homeostasis secondary to the cardiac hypertrophic process.