title: Caffeine-induced contracture in oesophageal striated muscle of normotensive and hypertensive rats.
abstract: To elucidate whether properties of the sarcoplasmic reticulum are altered, not only in vascular smooth muscle, but also in visceral striated muscle of spontaneously hypertensive rats (SHR), caffeine-induced contractures in oesophageal striated muscle of Wistar Kyoto rats (WKY) and stroke-prone SHR (SHRSP) were compared. In both preparations, 30 mM caffeine induced a contracture with two components. The second component, which was diminished by extracellular Ca(2+) removal or Ni(2+) but not by verapamil, was much smaller in SHRSP. Both components and differences between WKY and SHRSP coincided with changes in intracellular Ca(2+). Although membrane potential was identical between these preparations, caffeine induced slight depolarization only in WKY preparations. Similar depolarization was observed with 10 mM K(+), which induced no contraction. It is suggested that the first and the second components of caffeine-induced contracture were induced by Ca(2+) released from sarcoplasmic reticulum and by Ca(2+) that entered through channels activated by sarcoplasmic reticulum Ca(2+) depletion, respectively. In SHRSP preparations, Ca(2+) from the latter pathway was clearly decreased, although this change is thought not to be related to the initiation of hypertension. These results suggest that Ca(2+) handling properties of cell membrane and sarcoplasmic reticulum are generally altered in muscles of SHRSP.
authors.affiliation: Department of Anatomy and Physiology, Faculty of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Osaka Higashiosaka 577-8502, Japan.
authors.forename: Fumiko
authors.initials: F
authors.lastname: Sekiguchi
authors.forename: Kyoko
authors.initials: K
authors.lastname: Kawata
authors.forename: Mayumi
authors.initials: M
authors.lastname: Komori
authors.forename: Satoru
authors.initials: S
authors.lastname: Sunano
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D004947:Esophagus / Q000187:drug effects / Q000502:physiology / Q000503:physiopathology; D006973:Hypertension / Q000503:physiopathology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology / Q000503:physiopathology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012433:Ryanodine / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D000697:Central Nervous System Stimulants; D012433:Ryanodine; D002110:Caffeine; D014700:Verapamil; D002118:Calcium