Potentiation of adenosine 5'-triphosphate calcium responses by diadenosine pentaphosphate in individual rat cerebellar astrocytes.
The calcium responses induced by adenosine 5'-triphosphate (ATP) were examined in single cerebellar type 1 astrocytes by fura-2 microfluorometry. ATP elicited fast and transient increases of intracellular calcium concentration ([Ca2+]i) even in the absence of extracellular calcium, indicating the involvement of metabotropic purinoceptors. The co-stimulation with P1P5-di(adenosine-5')pentaphosphate (Ap5A; 0.1 microM) potentiated ATP-metabotropic calcium responses. After this preincubation ineffective concentrations of ATP triggered 40% of maximal response. Co-stimulation with Ap5A and ATP was mandatory. The potentiated response to ATP was also independent of extracellular Ca2+ and was maintained for long periods of time (h). These results show a relevant interaction of purinoceptors that may imply a novel mechanism of action for diadenosine polyphosphates.
Jiménez
A I
AI
Departamento de Bioquimica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.
Castro
E
E
Delicado
E G
EG
Miras-Portugal
M T
MT
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D002531:Cerebellum / Q000378:metabolism*; D015226:Dinucleoside Phosphates / Q000494:pharmacology*; D004357:Drug Synergism; D004533:Egtazic Acid / Q000494:pharmacology; D007700:Kinetics; D051381:Rats; D017208:Rats, Wistar
D015226:Dinucleoside Phosphates; C012275:P(1),P(5)-di(adenosine-5'-)pentaphosphate; D004533:Egtazic Acid; D000255:Adenosine Triphosphate; D002118:Calcium