Stimulation of thyroid function by several pituitary hormones results in an increase in plasma thyroxine and reverse triiodothyronine in tilapia (Tilapia nilotica)

General and Comparative Endocrinology
N ByamunguE R Kühn

Abstract

In this study, intravenous injection of several doses of porcine follicle stimulating hormone (pFSH: 0.002, 0.01, 0.05, and 0.5 micrograms/g body wt), bovine TSH (bTSH: 0.5 micrograms/g body wt), and ovine growth hormone (oGH: 0.04, 0.02, and 0.4 microgram/g body wt) stimulated an increase in plasma thyroxine (T4) and reverse triiodothyronine (rT3) in tilapia. This effect occurred in a dose-dependent manner. pFSH was the most potent in stimulating thyroid function. The dose of 0.002 microgram pFSH/g body wt increased plasma levels of T4 over control levels (2.59 +/- 0.16 ng/ml) about 2.5-fold within 4 hr, whereas a concentration of 0.5 micrograms/g body wt caused a great and prolonged increase of T4 and rT3 levels. Control levels (2.59 +/- 0.16 ng/ml for T4 and 40.37 +/- 8.60 pg/ml for rT3) were increased 19- and 22-fold respectively, over 24 hr. An increase of T4 and rT3 levels occurred also after injection of total hypophyseal extract and Con A II glycoprotein fraction of a tilapia pituitary homogenate, whereas the protein fraction failed to alter plasma concentrations of T4 and rT3. rT3 levels were also significantly increased at 2 hr, but not at 1 hr, after injection of T4. Basal T3 levels (1.90 +/- 0.22 ng/ml) were reduced...Continue Reading

References

May 1, 1985·General and Comparative Endocrinology·C L BrownM H Stetson
Jun 1, 1983·General and Comparative Endocrinology·J G EalesS Shostak

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Citations

Apr 1, 1996·Comparative Biochemistry and Physiology. Part B, Biochemistry & Molecular Biology·L R BerghmanF Vandesande
Jan 16, 2002·Comparative Biochemistry and Physiology. Toxicology & Pharmacology : CBP·P RoyS Bhattacharya
Jun 18, 1998·Annals of the New York Academy of Sciences·V M DarrasE R Kühn
Aug 18, 2006·General and Comparative Endocrinology·Chaminda N WalpitaSerge Van der Geyten

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