Karaki H, Nakagawa H, Urakawa N
Arch Int Pharmacodyn Ther. 1986 Jul;282(1):93-107.
Effects of Sr substitution for Ca on the contractions due to Ca influx in the aortae of rabbit and rat and the guinea-pig taenia coli were examined in order to characterize the pathways of Ca influx activated by either high K or receptor agonists. In normal solution containing Ca, high K increased both muscle tension and 45Ca uptake in rabbit and rat aortae and guinea-pig taenia. In Sr-substituted solution, high K also induced contractions accompanied by the increases in 89Sr uptake. Noradrenaline induced sustained contraction and increase in 45Ca uptake in normal solution whereas it induced only small contraction accompanied by small increase in 89Sr uptake in Sr-substituted solution in the aortae. Histamine increased neither muscle tension nor 89Sr uptake in Sr-substituted solution although it increased muscle tension as well as 45Ca uptake in normal solution in taenia. Ca and Sr both induced contraction in saponin-treated smooth muscles. The concentration of Sr to induce half maximum contraction was approximately 20 times higher than that for Ca in rabbit and rat aortae or 62 times higher in guinea-pig taenia. From these results, it is suggested that Ca and Sr enter the smooth muscle cells through K-activated channels and induce contraction whereas noradrenaline- or histamine-activated channels are less permeable to Sr than to Ca.
为了确定由高钾或受体激动剂激活的钙内流途径的特征，研究了用锶替代钙对兔、大鼠主动脉以及豚鼠结肠带因钙内流引起的收缩的影响。在含钙的正常溶液中，高钾可增加兔和大鼠主动脉以及豚鼠结肠带的肌张力和45钙摄取。在锶替代溶液中，高钾也可诱导收缩，并伴有89锶摄取增加。去甲肾上腺素在正常溶液中可诱导持续收缩并增加45钙摄取，而在主动脉的锶替代溶液中，它仅诱导小幅度收缩并伴有89锶摄取少量增加。组胺在锶替代溶液中既不增加肌张力也不增加89锶摄取，尽管它在正常溶液中可增加结肠带的肌张力以及45钙摄取。钙和锶均可诱导皂素处理的平滑肌收缩。在兔和大鼠主动脉中，诱导半数最大收缩的锶浓度约比钙高20倍，在豚鼠结肠带中则高62倍。从这些结果推测，钙和锶通过钾激活通道进入平滑肌细胞并诱导收缩，而去甲肾上腺素或组胺激活的通道对锶的通透性比对钙的通透性低。
