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A voltage-clamp study on voltage-gated calcium channels translated in Xenopus oocytes by rat brain mRNA

Yao Yong, Zhu Hui, Yang Youshan, Bao Yongde

Shanghai Institute of Physioloyg, Academy Sinica. Shanghai 200031, China

Abstract

Voltage-gated calcium channels，expressed in Xenopas oocytes after injection of
rat brain mRNA，were studied by using voltage-clamp technique. The properties of
the calcium channels were characterized by barium current[I_(Ba)]passed through the channels. All oocytes used in this study were taken from five identified donors. Endogenous voltage-activated barium current measured in most oocytes from these donors were not detectable，or smalleer than 15 nA，mRNA was extracted from the whole brains of 10 day postnatal rats and microin jected into the oocytes. I_(Ba) increased gradually. during five days after mRNA injection. The maximum amplitude of the expressed voltage-activated barium current was usually larger than one hundred of nA on the third day after mRNA injection. In comparison，the expresion of voltage-activated barium current was hardly detectable in oocytes injected by mRNA extracted from brains of embryonic rats. The voltaged-dependence of activation and inactivation pharmacology of I_(Ba) were studied. It was found that I_(Ba) was inhibited potently by lanthanide cations [La~(+3)，Nd~(+3)，Srn~(+3)，Eu~(+3)，Gd~(+3)m, Dy~(+3)，Er~(+3)] at #mu# mol/L concentration level. L-type calcium channel ligands，nifedipineand Bay K 8644 inhibited I_(Ba),at 100 pmol/L，while another dihydropyridine ligand(±)nimodipine enhanced I_(Ba). at the same concentration.

Key words: Calcium channel;Xenopus oocytes;mRNA expression

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Citing This Article：

Yao Yong, Zhu Hui, Yang Youshan, Bao Yongde. A voltage-clamp study on voltage-gated calcium channels translated in Xenopus oocytes by rat brain mRNA. Acta Physiol Sin 1993; 45 (1): (in Chinese with English abstract).