In a mouse skeletal muscle model, endothelin-1 attenuates while nitric oxide amplifies developed force, suggesting endothelial cell products directly modulate skeletal muscle function.
Animal data preclude clinical application; leaves open direct endothelial modulation of skeletal muscle contractility in humans.
We tested the hypothesis that endothelin and nitric oxide (NO) alter the force developed by fast-twitch and slow-twitch mammalian skeletal muscle, using a mouse skeletal muscle preparation trimmed to approximately 50% of the original diameter to decrease diffusion distances. We suspended trimmed soleus (SOL) and extensor digitorum longus (EDL) muscles in Krebs-Henseleit buffer (27 degrees C; pH 7.4) gassed with 95% O2 -5% CO2. Muscles were stimulated once every 90 s for 500 ms at 50 Hz for SOL and 100 Hz for EDL. The force developed by trimmed SOL was 223.8 +/- 9.1 mN/mm2 and by EDL was 247.3 +/- 9.4 mN/mm2. Endothelin 1 (ET-1) had no effect on EDL but significantly accelerated the rate of decrease of developed force of SOL at concentrations of 10(-10) mol/L and higher within 10 contractions. When ET-1 was removed, force returned toward control value. Endothelin 3 (ET-3) had no effect on either muscle. S-Nitroso-N-acetylpenicillamine (SNAP), a source of NO, increased developed force over time in both muscles, with a threshold of 10(-6) mol/L. The effect was evident within 5 contractions in both muscles. Force remained elevated above control values after the removal of SNAP. Thus ET-1 attenuated and NO amplified mammalian skeletal muscle function.
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Murrant et al. (1995) studied this question.
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