COMPARISON OF ANP BINDING AND SENSITIVITY IN BRAINS FROM HYPERTENSIVEAND NORMOTENSIVE RATS

We compared the abundance and sensitivity of atrial natriuretic peptid es (ANP) receptors in the brains of spontaneously hypertensive (SHR) a nd Wistar-Kyoto (WKY) rats and examined the effect of blood pressure o n the abundance of brain ANP receptors in several other experimental r at models. Brain slices from SHR generated more guanosine 3',5'-cyclic monophosphate in response to ANP than brain slices from WKY rats. No differences were found in brain particulate guanylate cyclase activity in both strains of rats. In rat brain homogenates, we observed that A NP bound in a specific and saturable fashion to samples from WKY rats, but not in samples from SHR. In vitro receptor autoradiography reveal ed that ANP binding was reduced in the subfornical organ, the choroid plexus, and the paraventricular nucleus of SHR compared with WKY rat b rains. Correction of hypertension in SHR or induction of hypertension in other strains did not affect ANP binding in any of these brain regi ons. Altogether, our data suggest that the increased sensitivity of SH R brains to the action of ANP may be a consequence of factors other th an the abundance of receptors and that it is not secondary to the elev ation of blood pressure.