Fig. 5

Myofilament Ca²⁺ desensitization in hypertrophic male myocytes at the end of reperfusion is absent in females. a Cardiomyocyte survival plots throughout simulated ischemia and reperfusion. b Resting myocyte length decreased to a greater extent in male NHR cardiomyocytes compared with females, with this sex difference absent in the HHR. c At end reperfusion, male HHR cardiomyocytes maintain contractility yet exhibit significantly increased Ca²⁺. Female HHR myocytes show augmented contractility with substantially lower transient Ca²⁺. d Phase loop analysis shows male, but not female, HHR cardiomyocytes exhibit a modified Ca²⁺-shortening relationship. e Male HHR cardiomyocytes exhibit significantly lower level of myofilament Ca²⁺ sensitivity, with an approximate two to threefold increase in Ca²⁺ levels at 50 % myocyte relaxation. (*sex p < 0.05; #strain p < 0.05; †sex-strain interaction; §post hoc male vs female p < 0.05; mean ± SEM; n = 5–8 cells from four to six hearts/group)