Effects of starvation and refeeding on gonadotropin and thyrotropin subunit mRNAs in male Japanese quail

摘要

The contents of mRNAs encoding LHbeta-, FSHbeta-, TSHbeta- and common a-subunit precursor molecules were measured in food-deprived and subsequently re-fed male Japanese quail. Pituitary LHbeta, FSHbeta and common a mRNA levels were decreased by starvation, and increased to the control levels by re-feeding. The rates of decreases of LHbeta and common a mRNA levels were greater the corresponding rate for FSHbeta levels. Pituitary TSHbeta mRNA levels were not decreased by starvation, but increased transitorily by re-feeding. Plasma LH and triiodothyronine levels were decreased by starvation, and then increased to control levels by re-feeding, while plasma FSH and thyroxine levels did not show significant changes. Plasma LH and FSH levels showed positive correlations with pituitary common alpha and FSHbeta mRNA levels, respectively, while plasma thyroxine levels showed a negative correlation with TSHbeta mRNA levels. Hepatic weight was decreased slightly but significantly by starvation, and then showed a remarkable rebound after re-feeding was started. These results suggest that LH synthesis and secretion are more sensitive to starvation than FSH synthesis and secretion in Japanese quail, and that LH production recovered to initial levels within several days when birds were fully fed. Also, there is a possibility that the synthesis of TSH is accelerated transitorily by re-feeding. Furthermore, these results showed that there are different relationships between the plasma levels of LH, FSH, and TSH and the various hormone subunit mRNA levels. The remarkable change in hepatic weight leads us to assume that hepatic thyroid hormone metabolism is affected by starvation and re-feeding.