The Electrolyte-Excreting Activity of Adrenocortical Substances

INTRODUCTION DORFMAN, Potts and Fish (1947) have used the adrenalectomized rats’ excretion of administered radiosodium for the detection of small amounts of desoxycorticosterone and have found the radiosodium excretion useful in characterizing the activity of various steroid compounds (Dorfman, 1949). Since Na 24 has a relatively short half-life (14.8 hours) and Na 22 is not easily obtained, it occurred to us that the measurement of urinary sodium and potassium by flame photometry (Overman and Davis, 1947; Shapiro and Hoagland, 1948) might offer certain advantages. METHODS The technique of Dorfman et al. (1947) involves the collection of urine from radiosodium injected, adrenalectomized rats for six hours following the injection of 0.25 cc. of an oil solution of desox}rcorticosterone acetate. A careful study was made of the variables involved in such a procedure when measurement of total urinary Na (and K) is measured instead of radiosodium. It was found that a urine-collection period of 4 hours following DOCA administration was somewhat more accurate provided that certain precautions are observed.