Correlation between electrical activity and intracellular Ca2+ oscillations in GH3 rat anterior pituitary cells.
Simultaneous measurements of electrical activity and intracellular Ca(2+) levels were performed in perforated-patch current-clamped individual GH3 cells. Both in cells showing brief (<100 ms) and long action potentials (APs), we found a good correlation between the averaged intracellular Ca2+ concentration ([Ca2+]i) and AP frequency, but not between the mean [Ca2+]i and AP duration. Nevertheless, the magnitude of spontaneous Ca2+ oscillations was highly dependent on the size and duration of the APs. The decay of the Ca2+ transients was not slowed when the size of the oscillations was varied either spontaneously or after elongation of the AP with the K+ channel blocker tetraethyl ammonium. Furthermore, the recovery from Ca2+ loads similar to those induced by the APs was slightly retarded after treatment of the cells with intracellular store Ca2+-ATPase inhibitors. Among previous results showing that caffeine-induced [Ca2+]i increases are secondary to electrical activity enhancements in GH3 cells, these data indicate that the Ca2+ entry triggered via APs is the primary determinant of the [Ca2+]i variations, and that Ca2+-induced Ca2+ release has a minor contribution to Ca2+ oscillations recorded during spontaneous activity. They also point to modulation of electrical activity patterns as a crucial factor regulating spontaneous [Ca2+]i signalling, and hence pituitary cell functions in response to physiological secretagogues.
Giráldez
T
T
Departamento de Bioquímica y Biología Molecular. Edificio Santiago Gascón, Campus del Cristo, Universidad de Oviedo, Oviedo, Spain.
de la Peña
P
P
Gómez-Varela
D
D
Barros
F
F
D000200:Action Potentials; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D002460:Cell Line; D006873:Hydroquinones / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D013973:Thyrotropin-Releasing Hormone / Q000502:physiology
D006873:Hydroquinones; C019359:2,5-di-tert-butylhydroquinone; D013973:Thyrotropin-Releasing Hormone; D002118:Calcium