Identification and Expression Analysis of Thyroid Stimulating Hormone Receptor (TSHR) in Fish Gonads Following LHRH Treatment

Thyroid hormones (THs) play an important role in many physiological functions both in mammalian and non-mammalian vertebrates. The effect of THs is mediated by thyroid hormone receptors, which are members of nuclear hormone receptor super family. cDNA sequence of 816 bp mRNA of Thyroid stimulating hormone receptor (TSHR) was cloned from Clarias batrachus, which encoded a peptide of 272 amino acids. The deduced amino acid sequence showed high similarity to Clarias gariepinus and Ictalurus punctatus. Phylogenetic analysis of C. batrachus deduced amino acid sequence showed more similarity with C. gariepinus and I. punctatus. The qPCR result displayed that TSHR mRNA was highly expressed in brain, testis and ovary. mRNA expression level of TSHR was analysed after administration of three different dosages of sLHRH viz 0.02, 0.03 and 0.050 μg/g body weights respectively at different time points. The TSHR mRNA expression was upregulated both with respect to different dosages (maximum in 0.05 μg/g) and time intervals (maximum after 6 h) in all treatments. The higher expression of TSHR mRNA in gonads and upregulation of THSR mRNA expression level after sLHRH administration clearly shows the positive relation between Thyroid hormones and reproduction in fishes. This is first report of LHRH hormone effect on TSHR at molecular level in fish.