Plasma thyroxine levels in freshwater perch: influence of season, gonadotropins, and gonadal hormones

Chakraborti, Pradip ; Bhattacharya, Samir (1984) Plasma thyroxine levels in freshwater perch: influence of season, gonadotropins, and gonadal hormones General and Comparative Endocrinology, 53 (2). pp. 179-186. ISSN 0016-6480

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Official URL: http://dx.doi.org//10.1016/0016-6480(84)90240-5

Related URL: http://dx.doi.org/10.1016/0016-6480(84)90240-5

Abstract

Plasma thyroxine (T4) of a freshwater female perch Anabas testudineus (Bloch) has been measured by specific radioimmunoassay (RIA). Monitoring of plasma T4 throughout the year showed that July to early September (spawning stage) had the highest T4 and late September to January (postspawning stage) had the lowest T4. The plasma T4 cycle was coincident with the ovarian cycle. Treatment of intact perch with salmon gonadotropin (SG-G100) or ovine LH (500 ng/100 g body wt) markedly enhanced plasma T4 levels. Ovine FSH was without any effect. Ovarian steroids, estrone and 17β-estradiol (100 ng/100 g body wt), also significantly augmented T4 level whereas estriol or progesterone had no such effect. There was a striking fall of plasma T4 in ovariectomized fish. The drop of T4 due to ovariectomy could not be reversed by SG-G100 but administration of estrone or 17β-estradiol to ovariectomized fish effectively reversed the drop of plasma T4 level. These findings suggest that gonadotropin's stimulatory effect on perch thyroid is mediated via the release of ovarian steroids.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
ID Code:20406
Deposited On:20 Nov 2010 09:24
Last Modified:21 Jan 2011 04:56

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