Fig. 5.

Fig. 5.

Cardiomyocyte turnover in response to 3-day high-intensity swimming stress test. (A) Experimental protocol. Zebrafish were first exposed to water containing IdU for 24 h. They were then placed in the Ucrit flume, modified to house groups of fish at moderate water flow by removing the narrow channel insert. The exercise group were placed in running water at 3 BL sec⁻¹ for 72 h. The control groups were placed in an identical flume with no water flow (rest conditions). After 72 h in the flumes, all fish received 12 h of rest in holding tanks and were exposed to CldU for 24 h, and then culled. (B) Percentage of cardiomyocytes labelling with IdU or CldU in 7-month-old fish under high-intensity swimming (n=10) or rest conditions (n=10). (C) Percentage of cardiomyocytes labelled with IdU or CldU in 21-month-old fish under high-intensity swimming (n=7) or rest conditions (n=5). (D) Percentage of cardiomyocytes dual labelled with IdU and CldU in 7-month-old and 21-month-old zebrafish under rest and high-intensity swimming conditions. Sample numbers as in B and C. (E) Venn diagrams summarising CldU and IdU results. Diameter of circles indicates relative magnitude of thymidine analogue incorporation. Percentages indicate proportions of cycling cardiomyocytes within each group. (F) Percentage of cardiomyocytes immunolabelling with activated caspase 3 antibodies in 7-month-old zebrafish under rest (n=9) or exercise (n=8), and 21-month-old zebrafish under rest (n=10) or exercise (n=8) conditions. Data are mean±s.e.m. **P<0.02; ****P<0.0001; ns, not significant (one-way ANOVA).