Identification and quantitative analysis of the cell membrane MgィイD1[2+]ィエD1 transporter in cardiac and smooth muscles.

A fluorescent Mg-D12 + Mg-D1 indicator，furapOracle（mag-fura-2）， was loaded into smooth muscle cells of guinea-pig tenia cecum， and cytoplasmic Mg-D12 + Mg-D1 concentration （[Mg-D12 + Mg-D1] Mg-fura-2） was measured Lowering extracellular NaイイD1+イエD1 concentration （[NaイイD1+イエD1]イイD2）in the absence of CaイイD12+イエD1 caused gradual elevation of [MgイD12+イエD1]イD2，the rate was strongly dependent on [NaイイD1+イエD1]イD2 with the max？rate of rise of 0. 16？M./ s.We also measured [MgイD12+イエD1]イイD2iイエD2 in rat ventricular myocytes。[Mg伊D12+伊D1]伊D2 was elevated when cells were treated with ionomycin 10 mM extracellular Mg伊D12+伊D1（[Mg伊D12+伊D1]伊D2 o伊D2）。The rat of rise of [MgイD12+イエD1]イイD2iイD2 was reduced in the higher [NaイイD1+イエD1]イイD2 oイエD2。您的位置：知道173>>网络D12+网络D1。These results suggest the exixtence of the Na D1+网络D12+网络D1 transport （Na D1+网络D1-Mg网络D12+网络D1 exchange） in smooth muscle and cardiac muscle cells。The rate of Mg D12+イエD1 transport was estimated to be 0. 026 pmol/cmイD12イD1·s in tenia and 0. 085 pmol/cmイD12イD1· s in cardiac myocytes at 25\。It is unlikely that the NaイイD1+イエD1-CaイイD12+イエD1 exchanger is mainly responsible for this MgイD12+イエD1 transport， because only the slight NaイD1+イエD1-MgイD12+イエD1 exchange activity was served in the CCL39 cells overexpressing the NaイイD1+イエD1 exchanger.

A fluorescent MgィイD12+ィエD1 indicator, furaptra (mag-fura-2), was loaded into smooth muscle cells of guinea-pig tenia cecum, and cytoplasmic MgィイD12+ィエD1 concentration ([MgィイD12+ィエD1]ィイD2iィエD2) was measured. Lowering extracellular NaィイD1+ィエD1 concentration ([NaィイD1+ィエD1]ィイD2oィエD2)in the absence of CaィイD12+ィエD1 caused gradual elevation of [MgィイD12+ィエD1]ィイD2iィエD2,the rate was strongly dependent on [NaィイD1+ィエD1]ィイD2oィエD2 with the maximal rate of rise of 0.16μM./s.We also measured [MgィイD12+ィエD1]ィイD2iィエD2 in rat ventricular myocytes. [MgィイD12+ィエD1]ィイD2iィエD2 was elevated when cells were treated with ionomycin in 10 mM extracellular MgィイD12+ィエD1([MgィイD12+ィエD1]ィイD2oィエD2). The rat of rise of [MgィイD12+ィエD1]ィイD2iィエD2 was reduced in the higher [NaィイD1+ィエD1]ィイD2oィエD2. The net efflux of MgィイD12+ィエD1 from the loaded cells was also markedly inhibited by the presence of 140 mM NaィイD1+ィエD1.These results suggest the exixtence of the NaィイD1+ィエD1-dependent MgィイD12+ィエD1 transport (NaィイD1+ィエD1-MgィイD12+ィエD1 exchange) in smooth muscle and cardiac muscle cells. The rate of MgィイD12+ィエD1 transport was estimated to be 0.026 pmol/cmィイD12ィエD1・s in tenia and 0.085 pmol/cmィイD12ィエD1・ s in cardiac myocytes at 25℃. It is unlikely that the NaィイD1+ィエD1-CaィイD12+ィエD1 exchanger is mainly responsible for this MgィイD12+ィエD1 transport, because only the slight NaィイD1+ィエD1-MgィイD12+ィエD1 exchange activity was observed in the CCL39 cells overexpressing the NaィイD1+ィエD1-CaィイD12+ィエD1 exchanger.