ADRENAL KIDNEY AND GONADAL STEROIDOGENESIS DURING SEXUAL-DIFFERENTIATION OF A REPTILE WITH TEMPERATURE-DEPENDENT SEX DETERMINATION

Adrenal-kidney and gonadal steroidogenesis were studied during early development in the red-eared slider turtle, Trachemys scripta, which exhibits temperature-dependent sex determination. In vitro steroid secretion by adrenal-kidney-gonad complexes, (AKGs) incubated for 6 hr was determined by radioimmunoassay (RIA). AKGs from presumptive males and females secreted progesterone at developmental stages before (stage 15), during (stages 17 and 19), and after (stage 21) the temperature-sensitive period for sex determination, and progesterone secretion increased significantly throughout the period from stage 15 to 21. Presumptive male AKGs secreted significantly more progesterone than female AKGs at stage 19. Corticosterone secretion by AKGs was observed at stage 17 in males only, but in both sexes at stages 19 and 21. Testosterone, estradiol, androstenedione; and dehydroepiandrosterone secretion by AKGs was detected only at stage 21. Of the steroids measured, progesterone and corticosterone were consistently secreted at the highest levels. Although some sex differences were observed, no obvious patterns of sexually dimorphic steroid secretion from AKGs were apparent. Gonads from stage, 21, stage 24, and 10-day-old hatehlings from both presumptive sexes incubated with [7-3H]pregnenolone showed only weak precursor conversion, primarily to polar metabolites, in incubations as long as 24 hr. None of the steroids assessed by RIA of AKG incubates could be identified by TLC or HPLC analysis of the stage 21 and stage 24 gonadal incubates. However, progesterone was tentatively identified in incubates of 10-day post-hatch female gonads. For stage 21 females, AKGs were separated into gonadal and adrenal-kidney tissue (AK) components and incubated in vitro for 1, 3, and 18 hr. Secretion of progesterone, testosterone, estradiol, and corticosterone from gonads was nondetectable by RIA, whereas secretion of progesterone and corticosterone by AKs was evident at all three time points and testosterone was detected in the media after 18 hr of incubation. Tissues from these incubations were extracted and assayed for progesterone and testosterone; neither of these steroids was detected in gonads and only progesterone was detected in AKs. These results indicate that the gonads are relatively quiescent, whereas adrenal-kidney tissue is steroidogenically active before, during, and after the temperature-sensitive period for sex determination in T. scripta. © 1992.