Intracellular Ca²⁺ dynamics in isolated myocytes of Wistar and SHR.

<p>A) Twitch Ca²⁺ transient (CaT) amplitude. B) Caffeine (Caff)-induced CaT amplitude. C) and D) Twitch and Caff-induced CaT decay parameters (tau). The inset in panel D) shows typical records of Caff-induced CaT (left) and diastolic Ca²⁺ (right) in W and SHR at 15 mo and in SHRF. E) Ca²⁺ leak from the SR. CaT amplitude and SR Ca²⁺ content (Caff-induced CaT) were higher in SHR at 6, 9 and 15 mo than in W of the same age. These increases were not observed in SHRF. At 15 mo there was a significant decrease in Tau of CaT and Caff-induced CaT in SHR relative to W. Tau of Caff-induced CaT in SHRF significantly diminished with respect to 15 mo SHR. At 9 and 15 mo there was an increase in SR Ca²⁺ leak in SHR vs. W, which did not occur in SHRF. *p<0.05 with respect to W of the same age; #p<0.05 with respect to SHR at 3 mo of age; †p<0.05 with respect to SHR 15 mo; n≥16 from at least 3 animals per group.