Mechanisms of rise and decay of ADP-evoked calcium signal in MDCK cells.
We have studied the effects of ADP on intracellular calcium levels ([Ca2+]i) measured by fura-2 fluorimetry in Madin Darby canine kidney (MDCK) cells. ADP evoked [Ca2+]i rises dose-dependently by releasing Ca2+ from the inositol 1,4,5-trisphosphate (IP3)-dependent Ca2+ pool followed by capacitative Ca2+ entry. The Ca2+ signal consisted of a peak and a gradual decline which reached a plateau in the case of 0.1-1 mM ADP; a plateau was not seen in the response to 10 mM ADP. ADP acted by stimulating P2u and P2y receptors based on rank order of agonist potency: ATP = UTP > ADP > 2-methylthio-ATP > 2-methylthio-ADP > adenosine > alpha, beta-methylene ATP. Buffering by lysosomes and efflux via plasmalemmal Ca2+ pumps might play important roles in the decay of the Ca2+ signal. The Ca2+ signal was dramatically inhibited by 100 microM LaCl3.
Jan
C R
CR
Department of Medical Education and Research, Veterans General Hospital-Kaohsiung, Taiwan, ROC. crjan@isca.vghks.gov.tw
Ho
C M
CM
Wu
S N
SN
Tseng
C J
CJ
D000244:Adenosine Diphosphate / Q000494:pharmacology* / Q000502:physiology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects*; D002460:Cell Line; D004285:Dogs; D005456:Fluorescent Dyes; D016257:Fura-2; D007202:Indicators and Reagents; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007811:Lanthanum / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000494:pharmacology
D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D000244:Adenosine Diphosphate; D007811:Lanthanum; D000255:Adenosine Triphosphate; D001920:Bradykinin; D002118:Calcium; D016257:Fura-2; D014544:Uridine Triphosphate