Time course of the effect of adrenalectomy on transcortin binding characteristics: appraisal of different methods of calculation.

The time course effect of adrenalectomy on the transcortin-corticosterone association constant (KT), its concentration of binding sites (ST) and the corresponding binding constant (SAKA) of albumin has been investigated by equilibrium dialysis at 37 C on plasma samples collected 0, 3, 6, 12, 24, 48, 96 and 144 h after adrenalectomy in male adult rats. The data have been analyzed by 3 different methods: a graphical Scatchard analysis using bound over unbound versus bound as representation axes and 2 least squares minimization methods in which axes were, respectively, bound over total versus mass of corticosterone added and total versus unbound. Confidence regions can be computed in the last two methods allowing the statistical comparison of the different dialysis experiments. Results obtained by the three methods are quite similar and led to the conclusions that following adrenalectomy KT was constant while ST varied. The observed pattern was a decrease until the first 24 h followed by a rise reaching almost twice the control value at 144 h. It would also appear that SAKA decreases slightly within 24 h following adrenalectomy.