COMBINED EFFECTS OF AGE AND DIETARY-FAT ON BETA-1-RECEPTORS AND CA-2+ CHANNELS IN RAT HEARTS

Male Wistar rats were fed a standard diet or diets supplemented with 10% butter, 10% corn oil, or 10% cod liver oil from the age of 2 mo. At 7 and 24 mo of age, the fatty acid composition of total phospholipids was determined in ventricular crude sarcolemma preparations; binding capacity and affinity (1/K(d)) of [H-3]dihydroalprenolol and [H-3]nitrendipine binding were also determined. The arachidonic acid level was significantly higher at 24 mo than at 7 mo of age in the membrane phospholipids in rats fed no extra fat, but in rats fed fat-supplemented diets, age had no effect. Affinity of Ca2+ channels for [H-3]nitrendipine decreased significantly in all dietary groups between 7 and 24 mo of age, whereas the affinity of beta-1-receptors for [H-3]dihydroalprenolol increased in corn oil-fed rats. Density of beta-1-receptors decreased significantly in corn oil- and butter-fed rats and rats fed no extra fat between 7 and 24 mo of age, whereas the density of Ca2+ channels decreased significantly in corn oil-fed rats. We conclude that the antagonist binding properties of Ca2+ channels and beta-1-adrenergic receptors in rat hearts may change with age depending on the dietary fat.