A novel ryanodine sensitive calcium release mechanism in cultured human myometrial smooth-muscle cells.
In cultured human myometrial cells application of caffeine (1-30 mM) did not result in an elevation of intracellular Ca2+ ([Ca2+]i). Caffeine was found to reversibly inhibit both spontaneous and agonist-induced repetitive rises in [Ca2+]i possibly as a consequence of its ability to interfere with the binding of inositol trisphosphate (IP3) to the receptor on the sarcoplasmic reticulum. Brief applications of ryanodine (1-10 microM) were observed to elevate [Ca2+]i and repeated exposures to ryanodine could elicit Ca2+ transients of similar magnitude. Ryanodine was also observed to mobilise Ca2+ in cells bathed in nominally Ca(2+)-free solution. These observations suggest the presence of a novel type of ryanodine-sensitive Ca(2+)-induced Ca2+ release (R-CICR) system in human myometrial cells.
Lynn
S
S
Department of Physiological Sciences, Medical School, The University, Newcastle upon Tyne, UK.
Morgan
J M
JM
Gillespie
J I
JI
Greenwell
J R
JR
D000328:Adult; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D009215:Myometrium / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D012433:Ryanodine / Q000494:pharmacology*
D012433:Ryanodine; D002110:Caffeine; D002118:Calcium