Decreased aldosterone receptor affinity in aortic cells from the Fischer 344 rat

The Fischer 344 rat strain represents a uniform population that is immune to salt induced hypertension and resistant to mineralocorticoid hypertension. We have compared aldosterone binding in aortic cells cultured from salt-resistant Fischer 344 rats to that from salt-sensitive Wistar-Kyoto controls for aldosterone binding. Aortic smooth muscle cells of both strains contain two classes of aldosterone binding sites: corticoid receptor I with high affinity and low capacity and corticoid receptor II with low affinity and high capacity. The corticoid receptor I of Fischer 344 rats has a significantly (P less than 0.001) lower affinity than that of age and sex-matched Wistar-Kyoto controls, but the binding capacity was the same. There was no difference between the strains in the affinity or binding capacity of corticoid receptor II. These results indicate that mineralocorticoid binding may be important in susceptibility and resistance to hypertension and support the contention that mineralocorticoids regulate blood pressure in part by direct action on vascular smooth muscle cells.