Urinary excretion of free glucocorticosteroids and testosterone in the Mongolian gerbil (Meriones unguiculatus): effects of long-acting corticotrophin and human gonadotrophin.

1. Methods for the quantitative collection of 24-hr urines of small laboratory animals and for the measurement of urinary free glucocorticosteroids and testosterone are described. 2. Urinary glucocorticosteroids and testosterone were determined in 0.1-0.5 ml-aliquots of 1/100 diluted urines after kieselgur mini-column extraction. 3. Excretion of glucocorticosteroids and testosterone in undisturbed Mongolian gerbils was 329 and 13 ng/day, respectively. 4. Administration of long-acting (1-24)ACTH (20 IU/animal) increased glucocorticosteroid and testosterone excretion to about 2000 ng/day (glucocorticosteroids) and to about 30 ng/day (testosterone) over 3 days. 5. In animals injected with 100 IU/animal HCG, testosterone excretion was elevated to about 35-50 ng/day over 3 days. 6. As the results show, the measurement of urinary excretion of free glucocorticosteroids and testosterone is a reliable index of adrenal-gonadal function in the Mongolian gerbil. 7. Furthermore, in small laboratory animals, steroid measurements in 24-hr urines may be superior to determinations in plasma, since amounts of urinary steroid are relatively high and 24-hr urines can be collected over longer time periods without stressing the animals.