Involvement of guanine nucleotide and sodium in regulation of yohimbine and clonidine binding sites in the HT29 human colon adenocarcinoma cell-line.
Sodium and GppNHp, a GTP analogue, decrease the specific binding of the alpha 2-adrenergic agonist [3H]clonidine on membranes from the HT29 cells; affinity of the ligand for the receptor is also decreased. The effects of the two agents are additive. By contrast, combination of sodium and GppNHp increases the number of binding sites for the alpha 2-adrenergic antagonist [3H]yohimbine. Sodium and GppNHp also decrease the potency of epinephrine and clonidine to displace [3H]yohimbine from the alpha 2-adrenoceptors of the HT29 cells
D000230:Adenocarcinoma; D001667:Binding, Competitive / Q000187:drug effects; D002460:Cell Line; D003000:Clonidine / Q000378:metabolism*; D003110:Colonic Neoplasms; D004837:Epinephrine / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology*; D006801:Humans; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology*; D015016:Yohimbine / Q000378:metabolism*
D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D006165:Guanylyl Imidodiphosphate; D006160:Guanosine Triphosphate; D012964:Sodium; D003000:Clonidine; D004837:Epinephrine