A rapid and practical determination of aldosterone in urine by double isotope method.

A double isotope derivative method for urinary aldosterone determination was improved in terms of economy (to one fifth the original cost) and efficiency (to less than half the time) by a combination of several individual improvements. Aldosterone-4-14C was used as an indicator, eliminating the procedure of preparing aldosterone-14C-diacetate. 3H-acetylation was done after, instead of before, dichloromethane extraction and a thin layer-chromatography, to avoid unnecessary acetylation of abundant contaminants. The cost of radioisotope was thus reduced to one tenth. dlAldosterone diacetate, added as a carrier, was easily located on thin layers by ultraviolet light. Two dimensional thin layer, instead of repeating one dimensional paper chromatography, was employed for the purification, thereby shortening the time to one twentieth to thirtieth, and enabling to eliminate the exidation of the diacetate to the monoacetate. The specific radioactivity of 3H-acetic anhydride was determined by acetylation of dlaldosterone mixed with urine, instead of cortisone or dl-aldosterone, for both economy and calibration. One technician can thus work out with 4-8 samples a week. Aldosterone excretion in 24 hr, thus determined, was 10.99•}3.83 (S.D.)ƒÊg for normal subjects and 32.12•}8.38ƒÊg for preoperative primary aldosteronism with a postoperative decrease to 12.03•}4.10ƒÊg.