title: Opposite effect of ATP on contraction force of tonic and phasic skeletal muscles in frogs.
abstract: Experiments in vitro showed that ATP and adenosine equally suppressed contractions of frog m. sartorius, which belongs to the phasic type muscles. Adenosine receptors antagonist 8-SPT abolished the effect of adenosine, but did not change the effect of ATP. This fact proves the independence of signaling pathways of these purines. ATP produced an opposite effect on the tonic muscle m. cruralis and increased the force of its contraction. Adenosine produced an inhibitory effect on the force of m. cruralis contration. In this case, 8-SPT also eliminated the effect of adenosine, but did not change the effect of ATP. The potentiating effect of ATP was blocked by suramin, a nonselective antagonist of P2 receptors, which attests to their involvement into the effects of this purine. The opposite effects of purinergic regulation reflect fundamental differences in functional organization of phasic and tonic muscular systems. It was hypothesized that the increase in contraction force under the effect of ATP is a mechanism providing maitenance of the contracted state of tonic muscle without appreciable metabolic costs.
authors.affiliation: Department of Television and Multimedia Systems, National Research University, Kazan, Russia. sngrichin@mail.ru
authors.forename: S N
authors.initials: SN
authors.lastname: Grishin
authors.forename: R R
authors.initials: RR
authors.lastname: Kamaliev
authors.forename: A Yu
authors.initials: AY
authors.lastname: Teplov
authors.forename: A U
authors.initials: AU
authors.lastname: Ziganshin
mesh_terms: D000241:Adenosine / Q000378:metabolism* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D011895:Rana ridibunda; D018047:Receptors, Purinergic P1 / Q000378:metabolism; D015398:Signal Transduction; D013498:Suramin / Q000494:pharmacology; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D018047:Receptors, Purinergic P1; D013498:Suramin; C031433:8-(4-sulfophenyl)theophylline; D000255:Adenosine Triphosphate; D013806:Theophylline; D000241:Adenosine; D002118:Calcium