ISSN:
1432-2013
Keywords:
Carbachol
;
Adenosine triphosphate
;
Neurotensin
;
Fura-2
;
Intracellular Ca2+
;
Ca2+ influx
;
Mn2+
;
Verapamil
;
Ni2+
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Abstract In the present study we have investigated the mechanism of intracellular Ca2+ activity ([Ca2+]i) changes in HT29 cells induced by adenosine triphosphate (ATP), carbachol (CCH), and neurotensin (NT). [Ca2+]i was measured with the fluorescent Ca2+ indicator fura-2 at the single-cell level or in small cell plaques with high time resolution (1–40Hz). ATP and CCH induced not only a dose-dependent [Ca2+]i peak response, but also changes of the plateau phase. The [Ca2+]i plateau was inversely dependent on the ATP concentration, whereas the CCH-induced [Ca2+]i plateau increased at higher CCH concentrations. NT showed (from 10−10 to 10−7 mol/l) in most cases only a [Ca2+]i spike lasting 2–3 min. The [Ca2+]i plateau induced by ATP (10−6 mol/l) and CCH (10−5 mol/l) was abolished by reducing the Ca2+ activity in the bath from 10−3 to 10−4 mol/l (n=7). In Ca2+-free bathing solution the [Ca2+]i peak value for all three agonists was not altered. Using fura-2 quenching by Mn2+ as an indicator of Ca2+ influx the [Ca2+]i peak was always reached before Mn2+ influx started. Every agonist showed this delayed stimulation of the Ca2+ influx with a lag time of 23±1.5 s (n=15) indicating a similar mechanism in each case. Verapamil (10−6–10−4 mol/l) blocked dose dependently both phases (peak and plateau) of the CCH-induced [Ca2+]i increase. Short pre-incubation with verapamil augmented the effect on the [Ca2+]i peak, whereas no further influence on the plateau was observed. Ni2+ (10−3 mol/l) reduced the plateau value by 70%.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00374950
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