López J R, Alamo L, Caputo C, DiPolo R, Vergara S
Biophys J. 1983 Jul;43(1):1-4. doi: 10.1016/S0006-3495(83)84316-1.
Ionic calcium concentrations were measured in frog skeletal muscle fibers using Ca-selective microelectrodes. In fibers with resting membrane potentials more negative than -85 mV, the mean pCa value was 6.94 (0.12 microM). In fibers depolarized to -73 mV with 10-mM K the mean pCa was 6.43 (0.37 microM). This increase in the intracellular [Ca2+] could be related to the higher oxygen consumption and heat production (Solandt effect) reported to occur under these conditions. Caffeine, 3 mM, also produced an increase in the free ionic calcium to a pCa of 6.52 (0.31 microM) without changes in the membrane potential. Lower caffeine concentrations, 1 and 2 mM, did not change the fiber pCa. Lower Ca concentrations in the external medium effectively reduced the internal ionic calcium to an estimated pCa of 7.43 (0.03 microM).
使用钙选择性微电极测量青蛙骨骼肌纤维中的离子钙浓度。在静息膜电位比-85mV更负的纤维中，平均pCa值为6.94（0.12微摩尔）。在用10mM钾将纤维去极化至-73mV时，平均pCa为6.43（0.37微摩尔）。细胞内[Ca2+]的这种增加可能与在这些条件下据报道发生的较高氧消耗和产热（索兰特效应）有关。3mM的咖啡因也使游离离子钙增加至pCa为6.52（0.31微摩尔），而膜电位没有变化。较低浓度的咖啡因，1mM和2mM，不会改变纤维的pCa。外部介质中较低的钙浓度有效地将内部离子钙降低至估计的pCa为7.43（0.03微摩尔）。
