Diets with 40 of calories as fat with poly-unsaturated to saturated ratios of either 0.2 beef tallow (BT) diet or 1.0 mix (M) diet were fed to rats of both sexes. Groups were killed at 9, 12, 15, 18, and 21 mo. of age. To estimate the effects of age, sex and dietary fat on lactate dehydrogenase (LDH), activities of muscle type and heart type subunits were assayed biochemically in heart homogenates using differential substrate concentrations of 1.0 × 10−2M and 3 × 10−4M pyruvate, respectively. For comparison of methods, LDH activity was also determined histochemically in frozen sections of hearts, using lactate as a subs
展开▼
