Influence of viscosity and ionic strength on the reaction kinetics of aldosterone and androstendione and their specific antibodies.

This paper analyses the influence of viscosity and ionic strength on the kinetics and equilibrium of the reactions of (125)I labelled androstendione and aldosterone with their specific antibodies used in the radioactive immunoassay determination of such hormones. Bi-exponential and irreversible kinetics is found for androstendione, and single-exponential and reversible ones for aldosterone. The results of the viscosity analysis reflect clear negative influence on direct reaction rate. Ionic strength excerpts some influence but not in a significant way, which suggests that the variation resulting from the effect of the glycerol addition is not due to the influence of the dielectric constant of the solutions used. The apparent product of the electrical charges is 0.228 for aldosterone, and 0.230 and -0.230 for androstendione. Results show diffusive control for both cases.