Oscillations in cytosolic free Ca2+ induced by ADP and ATP in single rat hepatocytes display differential sensitivity to application of phorbol ester.
We have previously described differences in the oscillatory responses of cytosolic free Ca2+ concentration ([Ca2+]i) in hepatocytes to ADP and ATP, which we have interpreted as evidence that these two nucleotides are acting at distinct receptors. We show here that ADP- and ATP-induced oscillations are differentially sensitive to application of the phorbol ester 4 beta-phorbol 12,13-dibutyrate (PDB). ADP-induced [Ca2+]i oscillations are abolished by low concentrations of PDB (5-10 nM), whereas ATP-induced oscillations of long duration are refractory to PDB, even at greatly elevated concentrations (100 nM). The data illustrate a further difference in the actions of ADP and ATP, strengthening the argument that these agonists are not acting at the same receptor on rat hepatocytes.
Dixon
C J
CJ
Department of Human Anatomy and Cell Biology, University of Liverpool, U.K.
Cobbold
P H
PH
Green
A K
AK
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar
D015240:Phorbol 12,13-Dibutyrate; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D002118:Calcium