Transport of ketone bodies and lactate in the sheep ruminal epithelium by monocarboxylate transporter 1
Transport of ketone bodies and lactate in the sheep ruminal epithelium by monocarboxylate transporter 1
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DOI：
10.1152/ajpgi.00268.2001
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发表时间：
2002-11-01
影响因子：
4.5
通讯作者：
Gäbel, G
中科院分区：
文献类型：
--
作者：
Müller, F;Huber, K;Gäbel, G
由于短链脂肪酸在细胞内的强烈代谢，瘤胃上皮细胞产生大量的D-β-羟丁酸、乙酰乙酸和乳酸。这些酸必须从胞浆中挤出，以避免细胞内pH(pH(I))的干扰。用pH敏感的荧光染料2‘，7’-bis(2-carboxyethyl)-5(6)-carboxyfluorescein.对绵羊瘤胃上皮细胞的pH(I)进行了研究细胞外加入D-β-羟基丁酸酯、乙酰乙酸酯或乳酸(20 MM)可导致细胞内酸化。反之亦然，去除细胞外的D-β-羟基丁酸酯、乙酰乙酸酯或乳酸，在与相应的单羧酸预育后会导致pH(I)增加。PCMBS(400um)和根皮素(20um)对pH(I)下降和pH(I)恢复的初始速率均有明显抑制作用。对培养的细胞和完整的瘤胃上皮在mRNA和蛋白水平上检测是否存在质子连接的单羧酸转运体(MCT)。利用RT-PCR技术，在培养的瘤胃上皮细胞和瘤胃上皮细胞中检测到编码MCT1亚型的mRNA。用MCT1抗体对培养的瘤胃上皮细胞和位于瘤胃上皮基底层的细胞进行免疫染色。综上所述，我们的研究结果表明，MCT1在瘤胃上皮层基底层表达，可能是将酮体和乳酸与H+一起从胞浆中排出到血液中的主要机制。
Due to intensive intracellular metabolism of short-chain fatty acids, ruminal epithelial cells generate large amounts of D-beta-hydroxybutyric acid, acetoacetic acid, and lactic acid. These acids have to be extruded from the cytosol to avoid disturbances of intracellular pH (pH(i)). To evaluate acid extrusion, pH(i) was studied in cultured ruminal epithelial cells of sheep using the pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Extracellular addition of D-beta-hydroxybutyrate, acetoacetate, or lactate (20 mM) resulted in intracellular acidification. Vice versa, removing extracellular D-beta-hydroxybutyrate, acetoacetate, or lactate after preincubation with the respective monocarboxylate induced an increase of pH(i). Initial rate of pH(i) decrease as well as of pH(i) recovery was strongly inhibited by pCMBS (400 muM) and phloretin (20 muM). Both cultured cells and intact ruminal epithelium were tested for the possible presence of proton-linked monocarboxylate transporter (MCT) on both the mRNA and protein levels. With the use of RT-PCR, mRNA encoding for MCT1 isoform was demonstrated in cultured ruminal epithelial cells and the ruminal epithelium. Immunostaining with MCT1 antibodies intensively labeled cultured ruminal epithelial cells and cells located in the stratum basale of the ruminal epithelium. In conclusion, our data indicate that MCT1 is expressed in the stratum basale of the ruminal epithelium and may function as a main mechanism for removing ketone bodies and lactate together with H+ from the cytosol into the blood.