尼罗罗非鱼生长激素及其受体的cDNA克隆与mRNA表达的雌雄差异分析

In order to study sex differences in growth in the Nile tilapia (Oreochromis niloticus) we cloned the cDANs encoding growth hormone and growth hormone receptor from pituitary or liver RNA by Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and compared their expressions between male and female by Semi-Quantitative RT-PCR. The open reading fame of GH of Nile tilapia consists of 615 bp and encodes a putative protein of 204 amino acids while the open reading fame of GHR consists of 1 908 bp and encodes a putative protein of 635 amino acids. By Semi-Quantitative RT-PCR, we measured GH and GHR expression in different tissues of Nile tilapia. GH expression was only detected in pituitary while GHR expression occurred in all types of tissues we measured, and especially in liver, muscle, gonad, hypothalamus and thymus. Thus, by Semi-Quantitative RT-PCR, we further measured the mRNA levels of growth hormone in the pituitaries and growth hormone receptor in livers and muscles of male and female Nile tilapia growing at different rates. Significantly greater expression of GH in pituitaries and GHR in livers was measured in the males than in the females. These results show that different levels of GH and GHR transcription can explain the growth rate differences between male and female Nile tilapia.