The mechanism of Ca2+ release from the SR of permeabilised guinea-pig and rat ureteric smooth muscle.
Recent work has indicated that there is a major difference in the Ca2+ store of smooth muscle from rat and guinea-pig ureter; with the rat store being agonist-sensitive but ryanodine insensitive and the guinea-pig store being ryanodine sensitive but agonist insensitive [Th. V. Burdyga, M.J. Taggart, S. Wray, J. Physiol. 489 (1995) 327-335]. We have therefore examined directly the mechanism of Ca2+ release from the internal Ca2+ store (SR). Following permeabilisation with alpha-toxin or beta-escin the SR was Ca(2+)-loaded before application of carbachol or caffeine. Only carbachol evoked a transient contraction in rat ureter. The carbachol-induced contraction was blocked by heparin and cyclopiazonic acid (CPA) but not ryanodine. Only caffeine produced contraction in guinea-pig ureter, and this was blocked by ryanodine. Direct application of IP3 caused a small transient contraction in rat but not guinea-pig ureter. We conclude that rat ureter possesses only an IP3 sensitive store while guinea-pig ureter only has a ryanodine sensitive store.
Burdyga
T V
TV
Physiological Laboratory, University of Liverpool, UK.
Taggart
M J
MJ
Crichton
C
C
Smith
G L
GL
Wray
S
S
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002217:Carbachol / Q000494:pharmacology*; D002463:Cell Membrane Permeability; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004928:Escin; D006168:Guinea Pigs; D006493:Heparin / Q000494:pharmacology; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D012433:Ryanodine / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000502:physiology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D010738:Type C Phospholipases; D014513:Ureter / Q000187:drug effects / Q000502:physiology*
D004791:Enzyme Inhibitors; D007211:Indoles; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002110:Caffeine; D004928:Escin; D002217:Carbachol; D006493:Heparin; D010738:Type C Phospholipases; D000252:Calcium-Transporting ATPases; C000543:cyclopiazonic acid