Hydroxysteroid dehydrogenase activity associated with sexual differentiation in embryos of the turtle Trachemys scripta.
Many turtles exhibit temperature-dependent sex determination. We have examined the hypothesis that incubation temperature causes a differential expression of steroidogenic enzymes in embryonic turtles. The activities of three steroidogenic enzymes were studied histochemically in turtle (Trachemys scripta) embryos at different developmental stages: sexually undifferentiated (Stage 15), differentiating (Stage 17), and differentiated (Stage 26; i.e., hatchling). Steroidogenic enzymes were detected in several tissues prior to, during, and after gonadal differentiation in embryos incubated at both male-producing and female-producing temperatures. In all embryos, ene-5-3 beta-hydroxysteroid dehydrogenase (HSDH) was detected only in adrenal tissue. 3 alpha-HSDH was localized in adrenal tissue, as well as in the mesonephros and liver. 17 beta-HSDH was evident in mesonephric, hepatic, and gut tissues. In hatchlings, ene-5-3 beta-HSDH and 3 alpha-HSDH were evident in the adrenal gland, whereas 3 alpha-HSDH and 17 beta-HSDH were present in the mesonephros and liver. While there was some variation in the activities of these enzymes during development, no temperature-specific pattern was apparent. At no stage were the enzymes observed in genital ridge/gonad. Our results show that T. scripta embryos possess enzymes necessary for steroid hormone synthesis. The segregated distributions of the enzymes suggest that a multi-organ regulatory system may mediate embryonic steroidogenesis. Our results do not indicate the genital ridge/gonad the principle site of steroid synthesis, although it may possess other enzymes that influence steroidogenesis.
Thomas
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Department of Integrative Biology, University of California, Berkeley, California 947203.
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D000818:Animals; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism; D005260:Female; D005835:Genitalia / Q000196:embryology / Q000201:enzymology; D006913:Hydroxysteroid Dehydrogenases / Q000378:metabolism*; D008297:Male; D012733:Sex Differentiation / Q000502:physiology*; D013696:Temperature; D014018:Tissue Distribution; D014426:Turtles / Q000196:embryology / Q000378:metabolism*
D006913:Hydroxysteroid Dehydrogenases; D008058:Dihydrolipoamide Dehydrogenase