ALDOSTERONE - INTRACELLULAR RECEPTORS IN HUMAN HEART

It has been suggested that aldosterone exerts direct effects on heart functioning, in particular by inducing cardiac fibrosis. We examined h uman heart tissue for the expression of aldosterone receptors (mineral ocorticoid receptors, MRs) and of the MR-protecting enzyme, 11 beta hy droxysteroid dehydrogenase (11 beta HSD). In situ hybridization using cRNA probes specific for human MRs revealed the presence of mRNA encod ing for MRs in cardiomyocytes. Immunohistochemistry with specific anti bodies against the MR exhibited the expression of MR protein in cardio myocytes. In contrast, intramyocardial small blood vessels showed no e vidence of immunolabelling. A distinct 11 beta HSD activity, which was nicotinamide-adenine dinucleotide dependent, was also demonstrated in human cardiac tissue. These results illustrate that all the component s required for a specific aldosterone effect are present in the human heart.