Computerized approach using autoradiography to quantify atrial natriuretic peptide receptors in the DOCA-salt hypertensive rat kidney

The alteration of atrial natriuretic peptide (ANP) receptors was investigated in the kidney of deoxycorticosterone acetate (DOCA)-salt treated hypertensive rats. The absolute amount of renal ANP receptors was determined in a membrane homogenate binding study of rat whole kidneys. Administration of DOCA-salt led to a decrease in renal ANP receptors after 3 weeks (prehypertensive state) and 6 weeks (established hypertensive state) of treatment. In vitro macro-autoradiography (ARG) was then performed with [¹²⁵I]ANP to localize and to quantitate specific renal ANP receptors. ARG revealed that specific ANP binding was distributed mainly over the renal cortex with the inner medulla next in frequency. Renal ANP receptors were therefore quantified over the cortex and the inner medulla using the computerized microdensitometry of ARG. A significant reduction in renal ANP receptors was observed in the DOCA-salt treated rats after 3 and 6 weeks of treatment with decrements observed in both the cortex and inner medulla. These alterations may be related to the pathophysiology of hypertension.