Involvement of both calcium influx and calcium mobilization in growth hormone-induced [Ca2+]i increases in Chinese hamster ovary cells.
This study reports rapid effects of growth hormone (GH) on the intracellular free calcium concentration ([Ca2+]i) in Chinese hamster ovary (CHO) cells stably expressing rabbit GH receptor. [Ca2+]i was measured by spectrofluorimetric methods in single cells and membrane Ca2+ currents by patch clamp techniques in the whole-cell configuration. In individual CHO cells, bathed in a standard saline solution containing 2 mM Ca2+, basal [Ca2+]i was 191 +/- 27 nM (mean +/- S.D.; n=83). Short term administration of GH (100 ng/ml, 30 s) induced a [Ca2+]i increase in 54% of cells tested (n = 398 of 743). Responses were clearly heterogeneous. Maximum calcium increase varied from 16 to 853 nM and time to peak varied from 4 to 320 s. On examination of the [Ca2+]i increases, it was possible to define two different types of calcium responses to GH. Experimental manipulations of extracellular and intracellular calcium concentrations demonstrated that GH-induced calcium increases involved both calcium influx and calcium mobilization. Calcium influx, a long lasting, small amplitude (63 +/- 34 nM) response, was observed in 121 out of 398 cells (30%) whereas calcium mobilization, a transient, large amplitude (263 +/- 175 nM) response, was observed in 277 out of 398 cells (70%). Moreover, patch clamp data show that influx did not involve the dihydropyridine-sensitive calcium channels.
Boquet
G
G
Laboratoire de Neurophysiologie, Centre National de Recherche Scientifique UMR 5543, Université de Bordeaux, France.
Barakat
L
L
Paly
J
J
Djiane
J
J
Dufy
B
B
D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D006224:Cricetinae; D004095:Dihydropyridines / Q000494:pharmacology; D013006:Growth Hormone / Q000378:metabolism / Q000494:pharmacology*; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011817:Rabbits; D019284:Thapsigargin / Q000494:pharmacology; D014700:Verapamil / Q000494:pharmacology
D015220:Calcium Channels; D004095:Dihydropyridines; D019284:Thapsigargin; C038806:1,4-dihydropyridine; D013006:Growth Hormone; D014700:Verapamil; D002118:Calcium