Spontaneous oscillations of cytoplasmic free calcium ion concentration in cultured smooth muscle cells from guinea pig ileum.
The cytoplasmic free calcium ion concentration ([Ca2+]i) of cultured guinea pig ileum longitudinal muscle cells loaded with a fluorescent [Ca2+]i indicator, fura-2, was measured by digital ratio imaging microscopy. Spontaneous [Ca2+]i oscillations were observed in 25% to 80% of the cells, which differed with the batches of the cultured cells after 5 to 8 days in culture. The frequency and amplitude of the [Ca2+]i oscillations in each individual cell were usually regular, but heterogeneity between neighboring cells was observed. The spontaneous [Ca2+]i oscillations were also observed even after incubation of the cells under a serum-free condition for 72 hr. Exchange of extracellular solution to Ca(2+)-free solution containing EGTA or BAPTA immediately stopped the [Ca2+]i oscillations. The ratio of the oscillating cells was dependent on the extracellular calcium ion concentration ([Ca2+]o); and heterogeneity in the range of the [Ca2+]o to generate the [Ca2+]i oscillations was observed. An inorganic Ca(2+)-antagonist, LaCl3, immediately suppressed the [Ca2+]i oscillations, but the treatment with verapamil or nicardipine, Ca(2+)-channel blockers, did not have any effect on the [Ca2+]i oscillations. An inhibitor of the intracellular Ca2+ pump, thapsigargin, induced a transient increase in [Ca2+]i and then inhibited the spontaneous [Ca2+]i oscillations. Neomycin, a compound known to inhibit phosphoinositide turnover, inhibited the [Ca2+]i oscillations.(ABSTRACT TRUNCATED AT 250 WORDS)
Ohata
H
H
Department of Pharmacology, School of Pharmaceutical Sciences, Showa University, Tokyo, Japan.
Kawanishi
T
T
Kawanishi
M
M
Uneyama
C
C
Takahashi
M
M
Momose
K
K
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D016257:Fura-2; D006168:Guinea Pigs; D007082:Ileum / Q000378:metabolism; D008297:Male; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009355:Neomycin / Q000494:pharmacology*; D013729:Terpenes / Q000494:pharmacology*; D019284:Thapsigargin
D013729:Terpenes; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D009355:Neomycin; D002118:Calcium; D016257:Fura-2