title: A comparison of the effects of UTP and ATP on the Ca2+ release channel of skeletal muscle sarcoplasmic reticulum.
abstract: Heavy sarcoplasmic reticulum (SR) membrane fractions from rabbit and porcine skeletal muscle were incorporated into planar lipid bilayers and the activity of the Ca2+ release channels was recorded under voltage clamp, using Cs+ as the current carrier. The effects of the nucleotides adenosine triphosphate (ATP) and uridine triphosphate (UTP) on channel activity were studied at a holding potential of +30 mV. UTP (0.1-1.0 mM) had no effect per se on the conductance or the gating properties of the Ca2+ release channels. In contrast, ATP (> 0.1 mM) increased P(o), the open channel probability, and both tau o1 and tau o2, the open time constants, and decreased tau c1 and tau c2, the closed time constants. The Ca2+ channel conductance, however, was not affected by ATP. Ruthenium red (1-2 microM), a well-known inhibitor of the SR Ca2+ release channel, abolished the ATP-induced channel activation. These electrophysiological data provide support for our contention (G. Suarez-Kurtz et al. (1993). Anais da Academia Brasileira de Ciências, 65:330) that the UTP-induced tension in mammalian "skinned" muscle fibers is not due to stimulated release of SR-stored Ca2+ via the release channel.
authors.affiliation: Departamento de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Brasil.
authors.forename: G
authors.initials: G
authors.lastname: Suarez-Kurtz
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects* / Q000378:metabolism; D004594:Electrophysiology; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D011817:Rabbits; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D013552:Swine; D014544:Uridine Triphosphate / Q000494:pharmacology*
chemical_list: D015220:Calcium Channels; D000255:Adenosine Triphosphate; D014544:Uridine Triphosphate