Fig. 7
MetS-A swine showed greater SR store and VGCC function compared to lean and MetS/D-A swine. a After depolarizing the cell with an 80 mM K+ solution to induce calcium influx and maximal loading of the sarcoplasmic reticulum (SR) store, the SR store was released by activating ryanodine receptors with 5 mM caffeine. The time to half signal recovery was measured during caffeine wash-out and corresponds to the activity of calcium extrusion mechanisms. b A similar protocol was used with an additional exposure to a 2 mM barium solution, which enters the cell via voltage-gated calcium channels and binds to fura-2, but is not transported by Ca2+ ATPases. Barium as a [Ca2+]i surrogate thereby provides a more selective measure of Ca entry. c The measured SR store release from CSM in MetS-A swine is greater than that seen in MetS/D-A and lean swine. This is consistent with our previous findings which show biphasic calcium handling alterations in CSM as CAD progresses in severity. d Extrusion mechanism activity as measured by time to half recovery is impaired in MetS/D-A swine. e The activity of voltage-gated calcium channels as measured by barium influx is increased in CSM from MetS-A swine and decreases back to baseline in CSM from MetS/D-A swine. This, again, is consistent with the biphasic pattern seen in CAD progression. *p < 0.05 compared with lean swine; ‡p < 0.05 compared with MetS-A swine. (Lean = 6; MetS-A = 8; MetS/D-A = 8.)