Cardiorespiratory performance segregates into rat strains of inherited low- and high-capacity runners (LCRs and HCRs); during adulthood, this segregation remains stable, but widens in senescence and is followed by segregated function, health, and mortality. However, this segregation has not been investigated prior to adulthood. We, therefore, assessed cardiorespiratory performance and cardiac cell (cardiomyocyte) structure–function in 1- and 4-month-old LCRs and HCRs. Maximal oxygen uptake was 23% less in LCRs at 1-month compared to HCRs at 1-month, and 72% less at 4 months. Cardiomyocyte contractility was 37−56% decreased, and Ca²⁺ release was 34−62% decreased, in 1- and 4-month LCRs versus HCRs. This occurred because HCRs had improved contractility and Ca²⁺ release during maturation, whereas LCRs did not. In quiescent cardiomyocytes, LCRs displayed 180% and 297% more Ca²⁺ sparks and 91% and 38% more Ca²⁺ waves at 1 and 4 months versus HCRs. Cell sizes were not different between LCRs and HCRs, but LCRs showed reduced transverse-tubules versus HCRs, though no discrepant transverse-tubule generation occurred during maturation. In conclusion, LCRs show reduced scores for aerobic capacity and cardiomyocyte structure–function compared to HCRs and there is a widening divergence between LCRs and HCRs during juvenile to near-adult maturation.

中文翻译：

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遗传身体能力：从年轻到成年再到老年的差异不断扩大

心肺功能分为遗传性低能力和高能力跑步者（LCR 和 HCR）的大鼠品系；在成年期，这种隔离保持稳定，但在衰老过程中扩大，随后出现功能、健康和死亡率的隔离。然而，这种隔离在成年之前尚未得到调查。因此，我们评估了 1 个月和 4 个月大的 LCR 和 HCR 的心肺功能和心肌细胞（心肌细胞）结构功能。与 1 个月时的 HCR 相比，LCR 的最大摄氧量在 1 个月时减少了 23%，在 4 个月时减少了 72%。与 HCR 相比，1 个月和 4 个月的 LCR中心肌细胞收缩力下降了 37−56%，Ca ²⁺释放下降了 34−62%。发生这种情况是因为 HCR 在成熟过程中改善了收缩性和 Ca ²⁺释放，而 LCR 则没有。在静止心肌细胞中，与 HCR 相比，LCR 在第 1 个月和第 4 个月显示出的 Ca ²⁺火花分别多出 180% 和 297% ，Ca ²⁺波分别多出 91% 和 38%。 LCR 和 HCR 之间的细胞大小没有差异，但与 HCR 相比，LCR 的横管减少，尽管在成熟过程中没有出现差异的横管生成。总之，与 HCR 相比，LCR 在有氧能力和心肌细胞结构功能方面得分较低，并且在青少年到接近成年的成熟过程中，LCR 和 HCR 之间的差异越来越大。