Corticosterone kinetics in the young rat

The aim of this study was to determine the ontogeny of the metabolic clearance rate (MCR) and secretion rate (SR) of corticosterone in infant rats. MCR was determined through evaluation of the plasma disappearance curve after a single injection of labelled steroid in a trace amount. Regression analysis o-f the disappearance data enabled the measurement of the half-life of disappearance (T1/2) and volume of distribution (VD) of corticosterone from which MCR was calculated. Secretion rate (SR) was calculated on the basis of MCR and the steady-state concentration of corticosterone. The kinetic parameters were measured at 12, 15-16, and 22 days of age. There was a significant decrease with age in T1/2 and VD however, MCR was not significantly affected. SR was increased significantly with age in stressed animals although SR was found to remain unchanged under basal conditions. [...]