[Effect of multiple hydrocortisone administrations on the kinetics of 22Na in slices of rat cerebral cortex].

The dynamics of 22-Na efflux from slices of rat brain cortex incubated in McIlwains medium was studied with the aid of improved compartmental analysis. Hydrocortisone (HC) was injected during 8 days. The isotope efflux followed 3-exponential kinetics. The kinetic analysis was made on the basis of 3-compartmental models of Na exchange. Administration of HC decreased the content of Na in fast-exchanged (extracellular) fraction and increased its content in the slow-exchanged (intracellular) fractions. HC elevated the speed constants of intercompartmental Na flows for intracellular fractions, especially the influx constants. The values of stationary Na flows between extra- and intracellular compartments were significantly increased. The data obtained are discussed with regard to direct action of HC on ionic exchange in tissue.