抄録
Common carp (Cyprinus carpio L.) were acclimated to 30°C from 20°C over 24 h and maintained at that temperature for 35 days. Changes in the expression of mRNA transcripts for fast myosin heavy chain (MyHC) isoforms, E12 of the E protein, and myogenic regulatory factors belonging to the MyoD (MyoD, myogenin, myf-5) and myocyte enhancer factor-2 (MEF2A, MEF2C) gene families were investigated in the fast myotomal muscle using northern blot analysis. Myofibrillar Mg2+-ATPase activity gradually declined over 21 days and was significantly different from the starting level after only 3-5 days. Over the same time period there was a dramatic decrease in the mRNA transcripts of the MyHC isoform predominantly expressed in cold-acclimated carp (10°C-type MyHC) and a significant increase in the transcripts of the MyHC isoform predominantly expressed in warm-acclimated carp (30°C-type MyHC). The levels of myogenin mRNA transcripts almost doubled over 3-7 days before declining to 30% of the starting levels for the remainder of the experiment. While the levels of E12 mRNA gradually decreased, MEF2A and MEF2C mRNA transcripts showed a significant decrease over 24 h and then stabilized at the lower levels. In contrast, the levels of MyoD mRNA were not affected by temperature acclimation. The possible role of myogenic regulatory factors in the expression of temperature-specific isoforms of MyHC in common carp is briefly discussed.
