Developmental profiles of protective mechanisms of heart against peroxidative injury.

The developmental profiles of the protective mechanisms of heart against peroxidative injury during neonatal growth was examined in the pigs of three different age groups. Lipid peroxidation expressed in terms of malonaldehyde formation was considerably higher in the pig hearts of the 8-10 day age group compared to that either by newborn or adult age groups. The four principal antioxidative enzymes, superoxide dismutase, glutathione peroxidase, glutathione reductase, and glucose-6-phosphate dehydrogenase (G6PD), were enhanced during early neonatal growth and, with the exception of G6PD, all other enzymes were further enhanced during further growth to adulthood. G6PD activity dropped significantly in adult heart. The phospholipid contents of myocardial membrane between newborn and week-old pigs did not vary significantly. Total phospholipids and phosphatidylcholine contents were significantly higher in adult heart compared to those in neonatal heart. The enzymes of phospholipid synthesis and degradation, fatty acyl CoA synthetase (FACS), phospholipase A2 (PLA2), lysophospholipase (LPL), and lysophophatidylcholine acyltransferase (LPCAT) increased during early neonatal growth. During further growth to adulthood, FACS decreased, PLA2 did not change, whereas both LPL and LPCAT increased significantly. Analysis of free fatty acids showed that palmitic and stearic acids decreased during the first week of growth, but increased during further growth to adulthood. Oleic acid did not change with aging, but arachidonic acid dropped in adult heart compared to that in neonatal heart. Linoleic, palmitoleic and free fatty acids increased dramatically during the first week of neonatal growth, but dropped thereafter. These results suggest that the unusual peroxidative status of the week-old pig heart is related to the presence of high concentrations of polyunsaturated fatty acids in the membrane phospholipids and not with the antioxidative defense system.