Temporal profile of β follicle-stimulating hormone, β luteinizing hormone, and growth hormone gene expression in the protandrous hermaphrodite, gilthead seabream, Sparus aurata

The temporal profile of βFSH, βLH, and growth hormone (GH) gene expression was measured throughout the periods of gonadal development, spawning, and post-spawning in the protandrous hermaphrodite gilthead seabream (sb), Sparus aurata (L.). Sampling was carried out monthly, covering a 8-31 month fish age. Pituitary RNA was extracted individually. The levels of βFSH, βLH, and GH mRNA were measured by dot blot hybridization using sb βFSH, βLH, and GH cDNA as probes and analyzed by computing densitometer (values standardized using individuals' β-actin pituitary mRNA levels). All three genes, βFSH, βLH, and GH were expressed throughout the year, with seasonal variations. However, transcript levels of βLH were consistently higher than those of βFSH. During the spawning season (which lasts for about 4 months), the mRNA levels of both βFSH and βLH subunits increased dramatically. βFSH peaked at the start of the spawning season for both males and females, and was significantly higher in males. As for βLH transcripts, a statistical interaction between sex and date was observed. No significant differences between males and females were found for GH. The pattern of GH expression levels was found to be correlated to that of βLH.