Synthesis and release of an acetylcholine-like compound by human myoblasts and myotubes.
1. Exogenously applied acetylcholine (ACh) is a modulator of human myoblast fusion. Using a chemiluminescent method, we examined whether an endogenous ACh-like compound (ACh-lc) was present in, and released by, pure human myogenic cells. 2. Single, freshly isolated satellite cells and proliferating myoblasts contained 15 and 0.5 fmol ACh-lc, respectively. Cultured myotubes contained ACh-lc as well. Also, ACh-like immunoreactivity was detected in all myogenic cells. 3. Part of the ACh-lc was synthesized by choline acetyltransferase (ChAT), as indicated by the reduction of ACh-lc content when bromoACh was present in the culture medium, and by direct measurements of ChAT activity. Also, ChAT-like immunoreactivity was observed in all myogenic cells. 4. Myoblasts and myotubes released ACh-lc spontaneously by a partially Ca(2+)-dependent mechanism. 5. The application by microperfusion of medium conditioned beforehand by myoblasts (thus presumably containing ACh-lc) onto a voltage-clamped myotube induced inward currents resembling ACh-induced currents in their kinetics, reversal potential, and sensitivity to nicotinic antagonists. 6. In vitro, the spontaneously released ACh-lc promoted myoblast fusion but only in the presence of an anticholinesterase. 7. Our observations indicate that human myogenic cells synthesize and release an ACh-lc and thereby promote the fusion process that occurs in muscle during growth or regeneration.
Hamann
M
M
Division de Recherche Clinique Neuro-Musculaire, Hôpital Cantonal Universitaire, Genève, Switzerland.
Chamoin
M C
MC
Portalier
P
P
Bernheim
L
L
Baroffio
A
A
Widmer
H
H
Bader
C R
CR
Ternaux
J P
JP
D000109:Acetylcholine / Q000096:biosynthesis* / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D002459:Cell Fusion / Q000502:physiology; D002478:Cells, Cultured; D002648:Child; D002795:Choline O-Acetyltransferase / Q000378:metabolism; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D002999:Clone Cells; D005434:Flow Cytometry; D006801:Humans; D007150:Immunohistochemistry; D008163:Luminescent Measurements; D008870:Microtubules / Q000378:metabolism*; D008875:Middle Aged; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010830:Physostigmine / Q000494:pharmacology
D002800:Cholinesterase Inhibitors; D009124:Muscle Proteins; D010830:Physostigmine; D002795:Choline O-Acetyltransferase; D000109:Acetylcholine