Cellular expression of a sodium-dependent monocarboxylate transporter (Slc5a8) and the MCT family in the mouse kidney

Abstract

Expression analysis of transporters selective for monocarboxylates such as lactate and ketone bodies in the kidney contributes to understanding the renal energy metabolism. Distribution and expression intensity of a sodium-dependent monocarboxylate transporter (SMCT) and proton-coupled monocarboxylate transporters (MCT) were examined in the mouse kidney. In situ hybridization survey detected significant mRNA expressions of SMCT and MCT-1, 2, 5, 8, 9, 10, and 12. Among these, signals for SMCT, MCT2 and MCT8 were predominant; transcripts of SMCT were restricted to the cortex and the outer stripe of outer medulla, while those of MCT2 and MCT8 gathered in the inner stripe of outer medulla and the cortex, respectively. Immunohistochemically, SMCT was present at the brush border in S2 and S3 of proximal tubules, suggesting the active uptake of luminal monocarboxylates here. MCT1 and MCT2 immunoreactivities were respectively found baso-laterally in S1 and thick ascending limbs of Henle's loop. The cellular localization of transporters suggests the involvement of SMCT in the uptake of filtrated lactate and ketone bodies and that of MCTs in the transport of monocarboxylate metabolites between tubular cells and circulation, but the different distribution patterns do not support the notion of a functional linkage between SMCT and MCT1/MCT2.

<b>Cellular distributions of monocarboxylate transporters: a r</b><b>eview </b>

“…The stomach, small intestine, and large intestine were segmented into three, twenty, and five sections, respectively. types (MCT1 to MCT12) by an in situ hybridization technique (159); four subtypes (MCT2, MCT5, MCT8, and MCT9) displayed comparatively intense signals of mRNA, with the most intense expression being for MCT2 and MCT8. Weak but significant signals were detected for MCT1, MCT10, and MCT12.…”

“…The regional differences of the outer medulla, in agreement with the expression pattern of SMCT1 mRNA. Its expression is not found in S1 segment of the proximal tubules but starts to appear in S2 up to S3 (S3: the proximal straight tubules) (141,159) (Fig. 2d).…”

“…Among the other MCT subtypes, the existence of MCT5, MCT6, MCT8, MCT9, MCT10 (or TAT1) and MCT12 has been shown in the kidney (33, 55), but their cellular localization and expression intensities remain unknown. We, therefore, tried to confirm the expression intensities and sites of MCTs in mice (159). First, we compared mRNA expressions of various MCT sub-brain (18,110,112).…”

Cellular Expression of the Monocarboxylate Transporter (MCT) Family in the Placenta of Mice

“…were designed for each mRNA of mouse MCT1-MCT12, GLUT1-GLUT5, and CD147, as described in our previous studies [21][22][23]. CD147 is an important chaperone protein of MCT1 and MCT4 [18].…”

“…The results obtained in the mouse largely confirmed the expression pattern of MCT reported by Northern blot analyses in the human placenta, except for MCT6 and MCT8 whose signals were undetectable in the mouse. The placenta must be another organ with the multiple expressions of MCT members comparable to the intestine [28] and kidney [21], which are engaged in the active uptake and reabsorption of monocarboxylates as nutrients.…”