Steroid Concentration and Tissue Integrity as Factors Determining the Physiological Significance of Effects of Adrenal Steroidsin Vitro

Publisher Website
Google Scholar
Abstract
The effects of cortisol and deoxycorticosterone in vitro on glucose uptake by rat thymus preparations have been studied as a function of steroid concentration, and of physiological integrity of preparations. In fresh preparations, cortisol at concentrations of 10-7 and 10-6 [image], concentrations that correspond to physiological levels in plasma, significantly inhibits glucose uptake; this inhibition has been shown previously to have physiological significance. Deoxycorticosterone at these concentrations has negligible effects. At 10-4 [image] and higher concentrations the effect of deoxycorticosterone equals that of cortisol; no known physiological significance is associated with the effects of deoxycorticosterone. In preparations that have been damaged by storage, the effects of deoxycorticosterone remain the same as in fresh preparations, but those of cortisol are diminished drastically at all concentrations. The resulting pattern of steroid inhibitions, in which deoxycorticosterone at 10-4 and 10-5 [image] has about twice the effect of cortisol, and neither steroid has much effect at lower concentrations, closely resembles the pattern of effects that these steroids have been found to produce with a wide variety of tissue preparations. It is concluded that these latter effects probably represent unphysiological actions of steroids, and that in order to observe physiologically significant effects of glucocorticoids in vitro the integrity of tissue preparations must be preserved, and steroids must be used at concentrations that are sufficiently low so that physiological effects are not obscured by unphysiological effects.