CP55,940 increases intracellular Ca2+ levels in Madin-Darby canine kidney cells.
The effect of CP55,940, a presumed CB1/CB2 cannabinoid receptor agonist, on intracellular free Ca2+ levels ([Ca2+]i) in Madin-Darby canine kidney cells was examined by using the fluorescent dye fura-2 as a Ca2+ indicator. CP55,940 (2-50 microM) increased [Ca2+]i concentration-dependently with an EC50 of 8 microM. The [Ca2+]i signal comprised an initial rise and a sustained phase. Extracellular Ca2+ removal decreased the maximum [Ca2+]i signals by 32+/-12%. CP55,940 (20 microM)-induced [Ca2+]i signal was not altered by 5 microM of two cannabinoid receptor antagonists, AM-251 and AM-281. CP55,940 (20 microM)-induced [Ca2+]i increase in Ca2+-free medium was inhibited by 86+/-3% by pretreatment with 1 microM thapsigargin, an endoplasmic reticulum Ca2+ pump inhibitor. Conversely, pretreatment with 20 microM CP55,940 in Ca2+-free medium for 6 min abolished thapsigargin-induced [Ca2+]i increases. CP55,940 (20 microM)-induced intracellular Ca2+ release was not inhibited when inositol 1,4,5-trisphosphate formation was abolished by suppressing phospholipase C with 2 microM U73122. Collectively, this study shows that CP,55940 induced significant [Ca2+]i increases in canine renal tubular cells by releasing stored Ca2+ from the thapsigargin-sensitive pools in an inositol 1,4,5-trisphosphate-independent manner, and also by causing extracellular Ca2+ entry. The CP55,940's action appears to be dissociated from stimulation of cannabinoid receptors.
Chou
K J
KJ
Department of Medicine, Kaohsiung Veterans General Hospital, Taiwan.
Tseng
L L
LL
Cheng
J S
JS
Wang
J L
JL
Fang
H C
HC
Lee
K C
KC
Su
W
W
Law
Y P
YP
Jan
C R
CR
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002186:Cannabinoids / Q000494:pharmacology*; D002460:Cell Line; D003511:Cyclohexanols / Q000494:pharmacology*; D004285:Dogs; D004963:Estrenes / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D007202:Indicators and Reagents; D015544:Inositol 1,4,5-Trisphosphate / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D009025:Morpholines / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug / Q000819:agonists* / Q000037:antagonists & inhibitors
D002186:Cannabinoids; D003511:Cyclohexanols; D004963:Estrenes; D007202:Indicators and Reagents; D009025:Morpholines; D010880:Piperidines; D011720:Pyrazoles; D011760:Pyrrolidinones; D043882:Receptors, Cannabinoid; D011955:Receptors, Drug; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C103505:AM 251; C054649:3-(2-hydroxy-4-(1,1-dimethylheptyl)phenyl)-4-(3-hydroxypropyl)cyclohexanol; D015544:Inositol 1,4,5-Trisphosphate; C109925:AM 281; D002118:Calcium