Activation of P2Y receptors by ATP and by its analogue, ADPbetaS, triggers two calcium signal pathways in the longitudinal muscle of mouse distal colon.
Our previous research showed that ATP and adenosine 5'-O-2-thiodiphosphate (ADPbetaS) induce contractile effects in the longitudinal muscle of mouse distal colon via activation of P2Y receptors which are not P2Y(1) or P2Y(12) subtypes. This study investigated the nature of the P2Y receptor subtype(s) and the mechanisms leading to the intracellular calcium concentration increase necessary to trigger muscular contraction. Motor responses of mouse colonic longitudinal muscle to P2Y receptor agonists were examined in vitro as changes in isometric tension. ATP or ADPbetaS induced muscular contraction, which was not affected by P2Y(11) or P2Y(13) selective antagonists. Calcium-free solution or the calcium channel blocker, nifedipine, failed to modify the contractile responses to ATP or ADPbetaS, which were virtually abolished by depletion of calcium intracellular stores after repetitive addition of carbachol in calcium-free medium with addition of cyclopiazonic acid. Neomycin or U-73122, phospholipase C inhibitors, or 2-aminoethoxy-diphenylborate (2-APB), membrane-permeant IP(3) receptor inhibitor reduced the response to ATP, whilst ryanodine or ruthenium red, inhibiting calcium release from ryanodine-sensitive stores, abolished the response to ADPbetaS. Responses to maximally effective concentrations of ATP and ADPbetaS were not fully additive. Desensitisation with ADPbetaS antagonized the contractile effects of ATP, as desensitisation with ATP antagonized the response to ADPbetaS. In the longitudinal muscle of mouse distal colon, ATP and ADPbetaS induce muscular contraction via a P2Y receptor, coupled to differential signal pathways leading to intracellular calcium increase.
Zizzo
Maria Grazia
MG
Dipartimento di Biologia Cellulare e dello Sviluppo, Laboratorio di Fisiologia generale, Università di Palermo, Viale delle Scienze, Palermo, Italy.
Mulè
Flavia
F
Serio
Rosa
R
D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism; D018679:Cholinergic Agonists / Q000494:pharmacology; D003106:Colon / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism; D013873:Thionucleotides / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
D002121:Calcium Channel Blockers; D018679:Cholinergic Agonists; D004791:Enzyme Inhibitors; D053496:Inositol 1,4,5-Trisphosphate Receptors; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D019837:Ryanodine Receptor Calcium Release Channel; D013873:Thionucleotides; C030812:adenosine 5'-O-(2-thiodiphosphate); D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D010738:Type C Phospholipases; D000252:Calcium-Transporting ATPases