Effect of cholesterol feeding and gender on the response of the isolated rat heart to hypoxia

Abstract

The effect of hypoxic perfusion on isolated hearts from male and female rats fed either a control or 2% cholesterol supplemented diet was studied. Initiation of hypoxia produced a rapid decline in rate of hearts from either male or female animals irrespective of diet regimen. However, hearts from male rats fed a control diet exhibited a significantly higher (P less than 0.01) resting rate during normoxic perfusion when compared with hearts from cholesterol-fed animals. Hypoxia also produced a rapid loss of myocardial contractile force and this effect was influenced by neither diet treatment nor animal gender. Similarly, there was little change in time to peak height of developed tension due to diet. Contracture development during hypoxic perfusion was significantly higher in hearts from female rats fed a cholesterol-supplemented diet compared with hearts from control diet fed female animals, whereas no changes were observed due to diet in hearts from male animals. Coronary resistance was increased as a result of hypoxic perfusion. In hearts from cholesterol-fed male rats this effect was substantially attenuated. Conversely, cholesterol supplementation resulted in a higher (P less than 0.05) coronary resistance in hearts from female animals either during normoxic or the early period of hypoxic perfusion. Prostacyclin synthesis as measured by immunoreactive 6-keto-PGF1 alpha efflux did not differ between hearts from either male or female rats during normoxic perfusion. Hypoxia significantly reduced 6-keto-PGF1 alpha efflux from hearts of cholesterol-fed male rats whereas it produced no effect in any other treatment category. Our results demonstrate a substantial contribution of dietary cholesterol and animal gender in the response of the isolated rat heart to hypoxic perfusion.