The molecular regulation of exercised-induced muscle fibre hypertrophy in the common carp: Expression of MyoD,PCNA and components of the calcineurin-signalling pathway

摘要

Growth was investigated over 16 d in juvenile common carp (Cyprinus carpio L.) held in either static water (tank rested,TR_(16)) or exercised in a flume at 2.5-3.2 body lengths s~(-1) for 18 h a day (exercised,E_(16)).Relative to the start of the experiment (TR_0),the TR_(16) group showed a 31% increase in body mass (specific growth rate,1.57% d~(-1)),whereas there was no net change in the E_(16) group.There was,however,a significant exercise-induced hypertrophy of slow muscle fibres with average fibre cross-sectional area (F_(CSA)) increasing by 35% in the E_(16) group,compared with 11 % in the TR_(16) group.In contrast,F_(CSA) of fast muscle fibres increased by 34% in the TR_(16) group compared to just 18% in the E_(16) group.The relative concentrations and subcellular localisation of proteins hypothesised to play a role in the regulation of muscle growth were measured.MyoD concentration was similar in the TR_0,TR_(16) and E_(16) groups in both slow and fast muscle.However,there was a small (5%-10%) but statistically significant increase in nuclear localisation of MyoD in those groups showing a significant increase in F_(CSA) over the time course of the experiment.PCNA concentration was 31% and 12% higher in the TR_(16) than in either the TR_0 or E_(16) groups for slow and fast muscle,respectively.Exercise resulted in a approx 10% increase in nuclear factor of T-cells (NFAT2) concentration in slow muscle but no change in NFAT2 localisation.Calcineurin B concentration was similar in tank rested and exercised groups.The results do not support a major role for the calcineurin-signalling pathway in the regulation of muscle hypertrophy in the common carp.