We isolated and cloned a carp somatolactin SL DNA fragment, of which 78% of the nucleotides were identical to the corresponding salmon SL sequence.The results obtained upon spl 2control Northern blot hybridization of carp pituitary RNA allowed the identification of two transcripts as described for other fish.When the content of SL transcripts in pituitary sections from summer- and winter- acclimatized carp was quantified by in situ hybridization assays, we found no significant differences between the skylight quilt pattern two seasons.
In salmonids, plasma SL reaches higher levels in summer than in winter in synchrony with the water temperature cycle; in the eurythermal carp, however, the complex adaptive responses imposed by seasonal environmental changes do not seem to include the regulation of the somatolactin detected with the probe used at the transcriptional level in pituitary glands.