Endothelial cell products alter mammalian skeletal muscle function in vitro

Area of Science:

• Physiology
• Molecular Biology
• Pharmacology

Background:

• Skeletal muscle function is modulated by various signaling molecules.
• Endothelin (ET) and nitric oxide (NO) are vasoactive substances with potential roles in muscle physiology.

Purpose of the Study:

• To investigate the effects of Endothelin-1 (ET-1) and nitric oxide (NO) on the force developed by mammalian fast-twitch and slow-twitch skeletal muscles.
• To elucidate the distinct roles of ET-1 and NO in modulating skeletal muscle performance.

Main Methods:

• Utilized isolated mouse soleus (SOL) and extensor digitorum longus (EDL) muscles, trimmed to reduce diffusion distances.
• Muscles were stimulated in vitro under controlled conditions (Krebs-Henseleit buffer, 27°C, pH 7.4, 95% O2 -5% CO2).
• Assessed the impact of varying concentrations of ET-1 and S-Nitroso-N-acetylpenicillamine (SNAP, a NO donor) on muscle force development.

Main Results:

• ET-1 (10⁻¹⁰ mol/L and higher) significantly accelerated force decline in slow-twitch SOL muscle but had no effect on fast-twitch EDL muscle.
• The force reduction induced by ET-1 in SOL muscle was reversible upon removal of the substance.
• S-Nitroso-N-acetylpenicillamine (SNAP) (≥10⁻⁶ mol/L) increased developed force in both SOL and EDL muscles, with sustained elevation after SNAP removal.

Conclusions:

• ET-1 attenuates the function of slow-twitch mammalian skeletal muscle.
• Nitric oxide (NO) amplifies the function of both fast-twitch and slow-twitch mammalian skeletal muscles.
• These findings highlight the differential regulation of skeletal muscle contractility by ET-1 and NO.