Mechanisms involved in ATP-evoked Ca2+ oscillations in isolated human granulosa-luteal cells.
Using single-cell microfluorimetry, we have shown that ATP evoked repetitive Ca2+ oscillations in intact Fura-2 loaded human granulosa-luteal cells (hG/LCs) in the absence of extracellular Ca2+. Sustained increases in [Ca2+]i required extracellular Ca2+ and ATP depleted stores were refreshed by brief (2 min) incubation with external Ca2+. Basal [Ca2+]i was unaffected by caffeine (1 mM), but 20 mM caffeine inhibited ATP-evoked Ca2+ release in the absence of external Ca2+. Thimerosal (10 microM) evoked repetitive Ca2+ spikes, under Ca(2+)-free conditions, which fused to form an elevated plateau when external Ca2+ was replaced. Thimerosal-induced changes in [Ca2+]i were reversibly inhibited by the thiol reducing agent dithiothreitol (1 mM). The periodicity and amplitude of the [Ca2+]i oscillations produced by thimerosal and ATP differ. ATP- or thimerosal-evoked changes in [Ca2+]i were unaffected by dantrolene sodium (10 microM). The Ca(2+)-ATPase inhibitor thapsigargin (1 microM) increased [Ca2+]i and attenuated subsequent ATP-evoked changes in [Ca2+]i. We conclude that ATP stimulates an oscillatory release of Ca2+ from InsP3-sensitive stores in hG/LCs.
Squires
P E
PE
Department of Physiology, University of British Columbia, Vancouver, Canada.
Lee
P S
PS
Yuen
B H
BH
Leung
P C
PC
Buchan
A M
AM
D000255:Adenosine Triphosphate / Q000378:metabolism*; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002478:Cells, Cultured; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D003620:Dantrolene / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005470:Fluorometry; D006107:Granulosa Cells / Q000378:metabolism*; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008184:Luteal Cells / Q000378:metabolism*; D009125:Muscle Relaxants, Central / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D013849:Thimerosal / Q000494:pharmacology
D000697:Central Nervous System Stimulants; D004791:Enzyme Inhibitors; D009125:Muscle Relaxants, Central; D013849:Thimerosal; D002110:Caffeine; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases; D003620:Dantrolene; D002118:Calcium