PRELIMINARY EVIDENCE SUGGESTING VARIATIONS OF GTH-1 AND GTH-2 MESSENGER-RNA LEVELS AT DIFFERENT STAGES OF GONADAL DEVELOPMENT IN RAINBOW-TROUT, ONCORHYNCHUS-MYKISS

To study the variations of alpha and beta GtH 1 and 2 gene expression during gonadal development in male and female rainbow trout, chum salm on alpha and beta GtH 1 and 2 probes were used. The alpha subunit cDNA probe used is identical to the cDNA encoding the alpha subunit common to both GtH 1 and 2. Total RNAs were prepared from pooled pituitaries and the validation of the use of these probes for studying the variat ion of GtH mRNAs was made by Northern blot analysis. The quantitative determination of GtH mRNAs employed slot blot hybridization. In males and females, beta GtH 1 predominates in early stages of gonadal develo pment (spermatogonia A and previtellogenesis), beta GtH 2 being weakly expressed. Both beta GtH 1 and beta GtH 2 are expressed during prespe rmiation, spermiation, and the periovulatory period with a predominanc e of beta GtH 2. In both sexes alpha GtH variations follow beta GtH 2 variations. (C) 1995 Academic Press, Inc.