Role of [Ca2+]i in "Ca2+ stores depletion-Ca2+ entry coupling' in fibroblasts expressing the rat neurotensin receptor.
1. Transfected Chinese hamster ovary fibroblasts expressing the rat neurotensin receptor were used to study the 'Ca2+ stores depletion-Ca2+ entry coupling' which follows stimulation with neurotensin and liberation of InsP3. 2. This coupling could be dissociated in time. Firstly, stores depletion was produced by neurotensin or thapsigargin which caused a first [Ca2+]i transient in a Ca(2+)-free external medium. Secondly, readmission of external Ca2+ produced an influx of Ca2+ and a second [Ca2+]i transient. 3. Various concentrations of thapsigargin (20 nM to 1 microM) were used to produce complete stores depletion with small or large first peaks of [Ca2+]i. Upon return to external Ca2+, small or large second [Ca2+]i peaks were observed. The amplitudes of both peaks were positively correlated. 4. The Ca2+ entry which followed stores depletion could occur at very low basal values of [Ca2+]i, was accelerated by okadaic acid and inhibited by staurosporine and the calmodulin antagonist W-7. 5. It is concluded that the rise in [Ca2+]i during Ca2+ stores depletion is an essential parameter which determines the size of the subsequent Ca2+ entry.
Gailly
P
P
Department of Physiology, Catholic University of Louvain, Brussels, Belgium.
Hermans
E
E
Gillis
J M
JM
D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D006224:Cricetinae; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism / Q000502:physiology; D008345:Manganese / Q000378:metabolism; D009496:Neurotensin / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D051381:Rats; D018028:Receptors, Neurotensin / Q000096:biosynthesis* / Q000187:drug effects; D013268:Stimulation, Chemical; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D015220:Calcium Channels; D004791:Enzyme Inhibitors; D047428:Protein Kinase Inhibitors; D018028:Receptors, Neurotensin; D013729:Terpenes; D009496:Neurotensin; D008345:Manganese; D019284:Thapsigargin; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002118:Calcium