Interdependence of corticosterone and thyroid hormones in toad larvae (Bufo boreas). II. Regulation of corticosterone and thyroid hormones.

摘要: Typically, the role of corticosterone (B) in metamorphosis is considered secondary to that thyroid hormone, with B having only enhancing effects. In current study, we demonstrate relationship between hormones and much more complex thyroxine (T4) may depend on for some its functions. Tadpoles western toad (Bufo boreas) were treated various combinations (B), (T4), triiodothyronine (T3), a goitrogen (thiourea; Thio), corticoid synthesis inhibitor (metyrapone; MTP). Hormones extracted from individual tadpoles whole-body hormone levels determined by radioimmunoassay. B-treatment decreased ratio T4 T3, suggesting increased conversion endogenous T3. addition, combination resulted high whole body-levels also caused decrease body-thyroid (T4 T3), negative feedback hypothalamo-pituitary-thyroid axis T3 had similar effect, decreasing body-T4 levels. T4-treatment, but not body-B MTP-treatment prevented stimulatory effect production. alone blocked all steroid metabolism [3H]progesterone interrenal vitro, lowered three-fold vivo. Thio-treatment reduced B. Finally, suggest these results system which regulate own potency: increasing stimulates production, increases active form Rising then cause T4, removing These interactions help clarify mechanisms underlying morphological effects described previous study. © 1995 Wiley-Liss, Inc.