The molecular regulation of exercised-induced muscle fibre hypertrophy in the common carp: expression of MyoD, PCNA and components of the calcineurin-signalling pathway.
Growth was investigated over 16 d in juvenile common carp (Cyprinus carpio L.) held in either static water (tank rested, TR16) or exercised in a flume at 2.5-3.2 body lengths s-1 for 18 h a day (exercised, E16). Relative to the start of the experiment (TR0), the TR16 group showed a 31% increase in body mass (specific growth rate, 1.57% d-1), whereas there was no net change in the E16 group. There was, however, a significant exercise-induced hypertrophy of slow muscle fibres with average fibre cross-sectional area (FCSA) increasing by 35% in the E16 group, compared with 11% in the TR16 group. In contrast, FCSA of fast muscle fibres increased by 34% in the TR16 group compared to just 18% in the E16 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 TR0, TR16 and E16 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 FCSA over the time course of the experiment. PCNA concentration was 31% and 12% higher in the TR16 than in either the TR0 or E16 groups for slow and fast muscle, respectively. Exercise resulted in a approximately 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.
Martin
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CI
Gatty Marine Laboratory, School of Biology, University of St Andrews, St Andrews, Scotland, KY16 8LB, UK.
Johnston
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IA
D000818:Animals; D019703:Calcineurin / Q000378:metabolism*; D002347:Carps / Q000502:physiology*; D051379:Mice; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology / Q000378:metabolism; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000254:growth & development*; D017570:MyoD Protein / Q000378:metabolism*; D050778:NFATC Transcription Factors / Q000378:metabolism; D005082:Physical Exertion / Q000502:physiology*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000502:physiology*
D017570:MyoD Protein; D050778:NFATC Transcription Factors; D018809:Proliferating Cell Nuclear Antigen; D019703:Calcineurin