title: Rat chromaffin cells lack P2X receptors while those of the guinea-pig express a P2X receptor with novel pharmacology.
abstract: 1. Whole-cell patch-clamp recording was used to determine the functional expression and pharmacological properties of P2X receptors in chromaffin cells dissociated from adrenal medullae of rats and guinea-pigs. 2. In rat chromaffin cells maintained in culture for 1 - 7 days, ATP and UTP failed to evoke any detectable response. 3. Guinea-pig chromaffin cells responded to ATP (100 microM) with a rapidly activating inward current. The amplitude of the response to ATP increased over the period cells were maintained in culture and so did the number of cells giving a detectable response, with 69% of cells responding after >/=4 days of culture. 4. The response to ATP desensitized slowly, and had a reversal potential of 2.5 mV. The EC50 for ATP was 43 microM. The potency order for ATP analogues was 2-MeSATP>ATP>ADP. Adenosine, UTP and alpha,beta-meATP were inactive. 5. Suramin (100 microM) and Cibacron blue (50 microM) inhibited the ATP (100 microM)-activated current by 51 and 47%, respectively. PPADS antagonized the response to ATP (100 microM) with an IC50 of 3.2 microM. 6. The ATP concentration-response curve shifted to the left at pH 6.8 (EC50, 19 microM) and right at pH 8.0 (EC50, 96 microM), without changing the maximal response. Zn2+ inhibited the response to ATP (100 microM) with an IC50 of 48 microM. 7. This study indicates that expression of ATP-gated cation channels in chromaffin cells is species dependent. The P2X receptors in guinea-pig chromaffin cells show many characteristics of the P2X2 receptor subtype.
authors.affiliation: Autonomic Neuroscience Institute, Royal Free and University College Medical School, Royal Free Campus, Rowland Hill Street, Hampstead, London NW3 2PF.
authors.forename: M
authors.initials: M
authors.lastname: Liu
authors.forename: P M
authors.initials: PM
authors.lastname: Dunn
authors.forename: B F
authors.initials: BF
authors.lastname: King
authors.forename: G
authors.initials: G
authors.lastname: Burnstock
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000313:Adrenal Medulla / Q000166:cytology; D000818:Animals; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D004553:Electric Conductivity; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D020128:Inhibitory Concentration 50; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D018722:Nicotinic Agonists / Q000494:pharmacology; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058476:Receptors, Purinergic P2X2; D013045:Species Specificity; D014544:Uridine Triphosphate / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology
chemical_list: D018722:Nicotinic Agonists; C546403:P2rx2 protein, rat; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; D004246:Dimethylphenylpiperazinium Iodide; D000255:Adenosine Triphosphate; D015032:Zinc; D014544:Uridine Triphosphate