Proliferation of myogenic progenitor cells following feeding in the sub-antarctic notothenioid fish Harpagifer bispinis.

Feeding metabolism and the activation of myogenic progenitor cells were investigated in the fast myotomal muscle of the sub-Antarctic fish Hapagifer bispinis acclimatized to either simulated summer (10 degrees C; 18 h:6 h light:dark) or simulated winter (5 degrees C; 6 h:18 h light:dark) conditions. Ingestion of a single meal equivalent to 10% and 15% of body mass in simulated winter and summer groups, respectively, resulted in an average 2.6-fold and 3.6-fold increase in oxygen consumption, declining to 75% of peak values after 63 h and 46 h. In fasted individuals, the number of myogenic progenitor cells, identified by the expression of c-met, was not significantly different between simulated summer and winter fish, representing 6.6% and 5.8% of total myonuclei, respectively. However, the number of cells expressing myogenin was higher whereas the expression of MyoD was lower in winter than in summer groups. The ingestion of a single meal under winter and summer treatment regimes resulted in a significant increase in the number of cells expressing MyoD (51% and 111%) and PCNA (88% and 140%, respectively). This was followed by an increase in the abundance of c-met (74 and 85%) and myogenin (42 and 97%, respectively) positive cells, indicating the production of new myogenic progenitor cells and the commitment to differentiation of a number of them. These results show that the proliferation of myogenic progenitor cells can be induced by feeding in teleost fishes and that temperature and photoperiod influence the expression of myogenic regulatory factors.