Effects of strophanthidin on intracellular Ca2+concentration and cellular morphology of guinea pig myocytes

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Abstract
To study the role of cytosolic calcium concentration ([Ca2+]i) in the pathophysiology of Ca2+ overload, we used a digital image of calcium indicator signals (fura-2 fluorescence) from guinea pig myocytes. [Ca2+]i increased from 69(SEM 5) nmol·litre−1 (n = 15) to 204(45) nmol·litre−1 (n = 14) after 10 min perfusion with 100 μmol·litre−1 strophanthidin. The effects of strophanthidin on cellular morphology were associated with variable increases in [Ca2+]i of myocytes. [Ca2+]i was 263(9) nmol·litre−1 in the spontaneous contracting cells with “Ca2+ wave”, and 784(103) nmol·litre−1 in rounded cells. There was a significant relationship (r =0.77, p2+]i and shortening of longitudinal length of the cells. After 20 min pretreatment with 10 μmol·litre−1 ryanodine, strophanthidin (100 μmol·litre−1) did not cause spontaneous contractile activity, and induced a slower increase in [Ca2+]i than found previously with strophanthidin alone. We suggest that [Ca2+]i played a primary role in mediating irreversible injury in this study, and that the absolute value of [Ca2+]i was correlated with morphological changes. We also suggest that the Ca2+ release from the sarcoplasmic reticulum was related to the increase in [Ca2+]i and the spontaneous contracting activity.