Attenuation of myosin light chain phosphorylation and posttetanic potentiation in atrophied skeletal muscle

• Published in: Pflügers Archiv Vol. 434; no. 6; pp. 848 - 851
• Main Authors: Tubman, L A, Rassier, D E, MacIntosh, B R
• Format: Journal Article
• Language: English
• Published: Germany Springer Nature B.V 01.11.1997
• Subjects: Animals; Denervation; Electric Stimulation; Female; Muscle Contraction - physiology; Muscle, Skeletal - metabolism; Muscle, Skeletal - physiopathology; Muscular Atrophy - etiology; Muscular Atrophy - metabolism; Muscular Atrophy - physiopathology; Muscular system; Myosin Light Chains - metabolism; Phosphorylation; Proteins; Rats; Rats, Sprague-Dawley; Space life sciences; Spinal Cord - physiology
• ISSN: 0031-6768; 1432-2013
• DOI: 10.1007/s004240050474

Previously we have demonstrated that the absence of staircase potentiation in atrophied rat gastrocnemius muscle is accompanied by a virtual absence of phosphorylation of the regulatory light chains (R-LC) of myosin. It was our purpose in the present study to determine if posttetanic potentiation and corresponding R-LC phosphorylation were also attenuated in disuse-atrophied muscles. Two weeks after a spinal hemisection (T12), twitch and tetanic contractile characteristics were measured in situ in control, sham-treated and atrophied (hemisected) muscles. Posttetanic potentiation 20 s after a 2 s tetanic contraction (200 Hz) was depressed in atrophied muscles (128.7 +/- 2.6%; mean +/- SEM) when compared to sham-treated (149.9 +/- 2.4%) and control (142.9 +/- 2. 7%) muscles. Atrophied muscles demonstrated a significant increase in R-LC phosphorylation from rest (0.05 +/- 0.04 moles of phosphate/mole of R-LC) to posttetanic conditions (0.21 +/- 0.03 moles of phosphate/mole of R-LC), and less phosphorylation than control and sham-treated muscles (0.43 +/- 0.06 and 0.49 +/- 0.03 moles of phosphate/mole of R-LC, respectively) after tetanic stimulation. The preservation of the potentiation-phosphorylation relationship in atrophied muscles is consistent with the hypothesis that R-LC phosphorylation may be the principal mechanism for twitch potentiation.