Austin C, Wray S
Physiological Laboratory, University of Liverpool, UK.
Pflugers Arch. 1994 Jun;427(3-4):270-6. doi: 10.1007/BF00374534.
Strips of rat mesenteric artery were loaded with carboxy-seminaphthorhodafluor (SNARF) to measure intracellular pH (pHi) and force simultaneously. pHi was altered by using weak acids and bases. Alkalinization produced an increase in force. For equal elevations of pHi a greater and faster increase of force was obtained in depolarized (high K+) than in non-depolarised preparations. Acidification produced little change in force unless the tissue was contracted (high-K+), in which case it elicited relaxation. Examination of the relationship between pHi and force in depolarized preparations showed that acidification produced a greater change in force than alkalinization. Removal of weak bases produced a transient acidification that was accompanied by a fall in force in all preparations. This was followed by a secondary contraction in depolarized preparations during the period over which pHi was acidic and being restored to resting values. Some preparations demonstrated a hysteresis in the relation between pHi and force. It is concluded that the relationship between pHi and force in mesenteric vascular smooth muscle is not constant but depends on the previous history of the preparation, and may involve differences in the interactions between H+, Ca2+ and the contractile machinery.
将大鼠肠系膜动脉条加载羧基-半萘罗丹明荧光染料（SNARF）以同时测量细胞内pH值（pHi）和张力。通过使用弱酸和弱碱来改变pHi。碱化导致张力增加。对于相同程度的pHi升高，去极化（高钾）制剂中张力的增加比非去极化制剂更大且更快。酸化除非组织处于收缩状态（高钾），否则对张力几乎没有影响，在这种情况下会引起舒张。对去极化制剂中pHi与张力之间关系的研究表明，酸化比碱化引起的张力变化更大。去除弱碱会产生短暂的酸化，所有制剂中的张力都会随之下降。随后在pHi呈酸性并恢复到静息值的期间，去极化制剂中会出现二次收缩。一些制剂在pHi与张力的关系中表现出滞后现象。得出的结论是，肠系膜血管平滑肌中pHi与张力之间的关系不是恒定的，而是取决于制剂的先前状态，并且可能涉及H⁺、Ca²⁺与收缩机制之间相互作用的差异。
