Accelerative effect of olive oil on adrenal corticosterone secretion in rats loaded with single or repetitive immersion-restraint stress

The present study was performed to clarify the effects of dietary oils on p hysiological and metabolic changes induced by a stress, using one-time or r epetitive water-immersion of restrained rats (single or repetitive stress) as an experimental stress load. In rats fed any test diets containing 20% o f the mixture of tripalmitin, tristearin, and corn oil (PSC), olive oil (OL I), safflower oil (SAF), and linseed oil (LIS) with repetitive stress loadi ng, body weight gains and food intakes were generally reduced, The weights of the thymus and spleen also declined, but the adrenal weights were enhanc ed. Particularly the increase in the adrenal weight of rats given the OLI d iet was greater than of rats supplied with other diets. When the rats were loaded with the single or repetitive stress, the concentrations of urea, li pid peroxide, and corticosterone in the plasma were increased in rats fed a ny of dietary oils. The rise of plasma corticosterone level was especially great in rats fed the OLI diet. The concentrations of total cholesterol (T- CHOL) and triglyceride (TG) in the plasma and liver generally tended to be higher in rats fed the OLI diet than in rats given the other diets with and without stress exposure. Plasma corticosterone concentration was correlate d to the adrenal weight (r=0.87, p<0.05). This study showed that OLI especi ally enhanced the adrenal weight in rats exposed to the repetitive stress a nd further raised the increased secretion of adrenal corticosterone in rats loaded with the single or repetitive stress compared with the other oils. The mechanism explaining these actions of OLI was inferred to be related to the levels of T-CHOL and TG in the plasma and liver generally enhanced by stress.