Murrant C L, Frisbee J C, Barclay J K
Department of Human Biology and Nutritional Sciences, University of Guelph, Canada.
Can J Physiol Pharmacol. 1997 May;75(5):414-22.
To investigate the effect of endothelial-derived products on the force of contraction of blood-perfused skeletal muscle, we infused S-nitroso-N-acetylpenicillamine (SNAP, 10(-4) M) (a nitric oxide (NO) donor), endothelin-1 (ET-1, 10(-8) M), N-acetylpenicillamine (NAP, 10(-4) M), or saline at a constant vascular concentration into the vascular bed of pump-perfused dog gastrocnemius-plantaris muscles in situ (n = 17). Muscles performed isometric twitch contractions at 0.5, 1.5, and 4 Hz and isometric tetanic contractions (150 ms, 50 Hz) at 12 and 40 contractions/min. We perfused the muscle at a constant pressure at rest and for the first 3 min of the 6-min contraction period, and then switched to constant flow perfusion and infused the substance over the remaining 3 min. Neither NAP nor saline had a significant effect on force of contraction or perfusion pressure. SNAP significantly attenuated developed force as compared with NAP at 40 contractions/min and at 1.5 and 4 Hz. The effect of SNAP on developed force was greater during twitch than tetanic contractions. ET-1 had no significant effect on twitch or tetanic developed force. To test for these results on another mammalian skeletal muscle preparation, we stimulated curarized trimmed mouse soleus in vitro for 500 ms at 50 Hz at either 2 or 4 contractions/min in the presence of SNAP (10(-4) M) or ET-1 (10(-9) M). SNAP, which increased force at 1 contraction/90 s, had no significant effect at the higher contraction frequencies. The inhibition by ET-1 at 2 contractions/min disappeared at 4 contractions/min. Therefore the effect of both NO and ET-1 on mammalian skeletal muscle appears to be dependent upon contraction pattern and frequency.
为研究内皮衍生产物对血液灌注的骨骼肌收缩力的影响，我们将血管活性浓度恒定的S-亚硝基-N-乙酰青霉胺（SNAP，10⁻⁴ M）（一种一氧化氮（NO）供体）、内皮素-1（ET-1，10⁻⁸ M）、N-乙酰青霉胺（NAP，10⁻⁴ M）或生理盐水注入原位泵灌注的犬腓肠肌-比目鱼肌血管床（n = 17）。肌肉在0.5、1.5和4 Hz频率下进行等长单收缩，在12和40次收缩/分钟频率下进行等长强直收缩（150毫秒，50 Hz）。我们在静息状态以及6分钟收缩期的前3分钟以恒定压力灌注肌肉，然后切换至恒定流量灌注，并在剩余3分钟内注入物质。NAP和生理盐水对收缩力或灌注压力均无显著影响。与NAP相比，在40次收缩/分钟以及1.5和4 Hz频率下，SNAP显著减弱了收缩力。SNAP对单收缩时收缩力的影响大于强直收缩。ET-1对单收缩或强直收缩力均无显著影响。为在另一种哺乳动物骨骼肌标本上验证这些结果，我们在存在SNAP（10⁻⁴ M）或ET-1（10⁻⁹ M）的情况下，以2或4次收缩/分钟的频率在体外对箭毒化的修剪后的小鼠比目鱼肌进行50 Hz、500毫秒的刺激。SNAP在1次收缩/90秒时增加了收缩力，但在较高收缩频率下无显著影响。ET-1在2次收缩/分钟时的抑制作用在4次收缩/分钟时消失。因此，NO和ET-1对哺乳动物骨骼肌的影响似乎取决于收缩模式和频率。
