ALDOSTERONE AND CARDIAC FIBROSIS - IN-VITRO STUDIES

Objective: Increased cardiac collagen is seen in uninephrectomised rats made hypertensive by aldosterone infusion and high salt, with the possibility of a direct effect of aldosterone at the level of the cardiac fibroblast. The aim of this study was to examine the effects of aldosterone, glucocorticoids, and angiotensin II on collagen production in a series of rat cardiac fibroblast cultures. Methods: Cardiac fibroblast cultures were established from neonatal and adult rats of Sprague-Dawley, WKY, and SHR strains, with collagen synthesis measured by incorporation of [H-3]proline into collagen. Cells were grown alone or co-cultured with cardiomyocytes, and exposed to aldosterone, glucocorticoids, or angiotensin II for 24-28 h before determination of [H-3]proline incorporation. Results: Aldosterone did not affect production of collagen; in contrast, angiotensin II increased, and the glucocorticoid agonist RU28362 suppressed, collagen production in cultured cardiac fibroblasts in the various rat strains. Conclusions: Aldosterone does not exert a direct effect on collagen synthesis in rat cardiac fibroblasts grown in culture. The increased cardiac collagen observed in vivo in aldosterone treated, salt loaded rats may thus represent secondary effects of aldosterone in this model.