Induction of rat pituitary thymidine kinase: another physiological response to oestradiol in the male?
Subcutaneous injection of oestradiol-17beta enhanced the thymidine kinase activity in the anterior pituitary of immature male rats, but did not alter the thymidylate synthetase level. The kinase activity reached a sharp maximum 36 hours after injection of the steroid and then decreased to its original value. The estimated minimum active dose was 0.020 mug per rat. The 17alpha isomer was inactive. Cycloheximide and actinomycin D, according to injection schedule, prevented the rise in activity, suggesting a regulation of pituitary thymidine kinase at the level of protein biosynthesis. The induced enzyme exhibited the same Km and the same thermal inactivation profile as the constitutive enzyme. With the doses of oestradiol required for induction of the enzyme, no significant variations of serum and pituitary LH and FSH concentrations were detected. Based on these and previous results it is suggested that, in the male pituitary, the concentration ratio of circulating oestrogens over androgens controls not only the secretory function but also the production of specific enzymes.
D000818:Animals; D001692:Biological Transport; D002540:Cerebral Cortex / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000378:metabolism / Q000494:pharmacology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D007700:Kinetics; D007986:Luteinizing Hormone / Q000378:metabolism; D009928:Organ Specificity; D010902:Pituitary Gland / Q000201:enzymology* / Q000378:metabolism; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000201:enzymology*; D051381:Rats; D013237:Stereoisomerism; D013937:Thymidine Kinase / Q000096:biosynthesis*; D013940:Thymidylate Synthase / Q000378:metabolism
D003609:Dactinomycin; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D003513:Cycloheximide; D013940:Thymidylate Synthase; D013937:Thymidine Kinase