Environmental factors regulating fish neurohormone genes

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Expression of Neurohypophysial HOrmone Genes in Salmonids :Teleostean neurohypophysial hormones are considered to be vasotocin (VT) and isosotocin (IT). Since salmonids are tetraploid, they may usually have at least a pair of genes for precursors of proteinaceous hormones, including VT and IT precursor genes. Hence antisense oligodeoxynucleotides which can recognize both of 2 types of mRNAs were synthesized as probes for an in situ hybridization study on effects of increase in the level of pro-VT mRNA was found in preotic neurosecretory neurons, suggesting a possible role of VT in fresh water adaptarion.The pattern of expression of 2 pro-VT and 2 pro-IT genes were examined by use of Northern blot analysis in rainbow trout, masu salmon, sockeye salmon and chum salmon. The hybridization signal for pro-IT-I was stronger than that for pro-IT-II in all species examined, whereas the pattern of VT gene expression was different among species. Such information is quite important in a future study to analyze regulatory mechanisms of hormonal gene expression in salmonids.Expression of Adenohypophysial Hormone Genes :Changes in the levels of gonadotropin precursor genes were examined in rainbow trout following gonadal maturation. Expression of genes from growth harmone and prolactin was also examined in pituitaries of rainbow trout in primary culture.