Effects of starvation on gonadotropin and thyrotropin subunit mRNA levels and plasma hormone levels in the male Japanese quail (Coturnix coturnix japonica)

Abstract

Contents of mRNAs encoding LHβ-, FSHβ-, TSHβ- and common a-subunit precursor molecules were measured in male Japanese quail deprived of food for three days. Plasma LH, FSH, thyroxine and triiodothyronine levels were also measured in the same birds. Plasma LH levels declined during the period of food deprivation. Levels in starved birds were not different from those in control birds after one day of starvation but were significantly lower after three days. Plasma FSH levels showed a similar decline, although the changes were not significant. Plasma thyroxine levels did not decrease during starvation, whilst plasma triiodothyronine levels decreased drastically and significantly soon after the start of starvation. All the hormone subunit mRNA contents in starved birds also decreased, with differences from control birds significant 3 days after the start of starvation. Plasma FSH levels showed a strong positive correlation with pituitary FSHβ mRNA levels, while plasma LH levels had a strong positive correlation with common α mRNA levels and practically no correlation or even a negative correlation with LHβ mRNA levels. These results suggest that starvation suppresses not only gonadotropin and thyrotropin secretion but also their synthesis in the pituitary gland. Furthermore, these results showed that FSH and LH have different synthesis and secretion dynamics in the Japanese quail. Contradicting results with TSHβ mRNA and thyroid hormones lead us to assume that starvation affects thyroid hormone metabolism in peripheral tissue, presumably in the liver.