Increases in intracellular calcium via activation of an endogenous P2-purinoceptor in cultured CHO-K1 cells.
1. Increases in intracellular calcium ([Ca2+]i) were measured in chinese hamster cultured ovary cells (clone, CHO-K1), by use of the fluorescent, calcium-sensitive dye, fura-2. 2. Addition of both ATP and UTP elicited rapid increases in [Ca2+]i due to mobilization from intracellular stores and calcium entry across the plasma membrane. 3. Omission of calcium from the extracellular medium and pre-incubation with the inorganic calcium channel blocker, nickel (Ni2+) prevented the calcium entry components of the responses. 4. Investigation of the concentration-response relationships of various analogues of ATP suggests the presence of a purinoceptor which cannot be characterized as P2X or P2Y. In addition, there appears to be a sub-population of P2Y-purinoceptors which do not cross-react with the 'nucleotide' receptor population. 5. Cross-desensitization and additivity experiments suggest that both ATP and UTP activate the same receptor. 6. Pre-incubation with the tumour-promoting agent, beta-phorbol-12,13 dibutyrate (PDBu), caused a reduction in the increases in [Ca2+]i, suggesting a role for protein kinase C in feedback inhibition of purinoceptor responses in this cell line. 7. In summary, we present evidence for the existence of an endogenous P2U-purinoceptor (or 'nucleotide receptor') which is linked to increases in [Ca2+]i in CHO-K1 cells.
Iredale
P A
PA
Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, Nottingham.
Hill
S J
SJ
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D018047:Receptors, Purinergic P1 / Q000187:drug effects / Q000502:physiology*; D014544:Uridine Triphosphate / Q000494:pharmacology
D018047:Receptors, Purinergic P1; D015240:Phorbol 12,13-Dibutyrate; D000255:Adenosine Triphosphate; D002118:Calcium; D014544:Uridine Triphosphate