Modulation by divalent cations of GABA rho 1 receptor from human retina expressed in Xenopus oocytes.
OBJECTIVE
To investigate functional homooligomeric GABA rho 1 receptors expressed in Xenopus oocytes and the modulation of divalent cations.


METHODS
GABA rho 1 cDNA from human retina was transcribed in vitro to obtain sense rho 1 mRNA, which was microinjected into Xenopus oocytes. Two-electrodes voltage clamp technique was performed to record GABA-induced currents.


RESULTS
Expressed receptors were found to have similar properties to GABAc receptors characterized in the retina. Cl-currents induced by GABA were blocked by picrotoxin instead of bicuculline. GABA-induced currents reversed at -19 +/- 2.5 mV, and EC50 was 3.3 mumol/L. Zn++ modulated GABA-induced currents with an IC50 = 9.6 mumol/L. Ni++, Cu++ and Cd++ inhibited GABA rho 1 obviously, too. Their rank order of potency was Zn++ > Ni++ > Cu++ > Cd++.


CONCLUSIONS
Zinc (10 mumol/L) inhibited GABA-induced currents in a competitive manner, and its action was sensitive to extracellular pH. Site-directed mutagenesis revealed that substitution of a single histidine residue (H44 and H48) failed to affect zinc sensitivity.
Wang
Q W
QW
Research Center of Basic Medicine, Wuhan Institute of Children Disease, Wuhan 430016, People's Republic of China. kinvinw@hotmail.com
Li
Z W
ZW
Wang
F
F
Yang
J Q
JQ
D000818:Animals; D001483:Base Sequence; D002413:Cations, Divalent / Q000494:pharmacology*; D017931:DNA Primers; D006801:Humans; D016297:Mutagenesis, Site-Directed; D009865:Oocytes / Q000378:metabolism; D018080:Receptors, GABA-B / Q000187:drug effects* / Q000502:physiology; D011994:Recombinant Proteins / Q000187:drug effects / Q000378:metabolism; D012160:Retina / Q000187:drug effects*; D014981:Xenopus
D002413:Cations, Divalent; D017931:DNA Primers; D018080:Receptors, GABA-B; D011994:Recombinant Proteins