Monocarboxylate transporter genes in the mammary gland of lactating cows

Abstract

This study is the first to examine the expression of the 14 monocarboxylate transporter genes (MCT1-MCT14) in the mammary gland of mammals. RT-PCR, Western blot, immunohistochemistry, and immunofluorescence confocal laser microscopy were applied in a comprehensive approach to assess the expression and cellular localization of MCTs in the mammary gland of lactating cattle. RT-PCR revealed the existence of nine MCT isoforms, namely MCT1, MCT2, MCT3, MCT4, MCT5, MCT8, MCT10, MCT13, and MCT14 in cow mammary gland. The amplified cDNA segments were confirmed by sequence analysis and deposited in the GenBank. Using the commercially available antibodies against MCT1-MCT8, Western blotting verified the protein expression of MCT1, MCT2, MCT3, MCT4, MCT5, and MCT8 in the cow mammary gland. The precise cellular localization of the identified MCT proteins showed that both MCT1 and MCT2 were basolaterally localized on the cow mammary alveolar epithelial cells. In contrast, MCT4 protein signal was expressed on the apical membrane of these alveolar epithelia. MCT8, however, was predominantly localized on the basolateral membranes of the lactocytes, along with its weak labeling on the apical membrane of the same cells. No immunoreactive staining for MCT3 and MCT5 proteins could be detected histochemically in lactating bovine mammary tissue. Additionally, we proved the colocalization of CD147 with both MCT1 and MCT4 on the boundaries of the cow mammary alveolar epithelia. The existence and localization pattern of MCT genes in the mammary gland of lactating cows suggest their possible involvement in the transport of essential elements required for milk synthesis and secretion.

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

“…Kirat and Kato (76) have detected expressions of MCT1, MCT2, MCT4, and MCT8 by immunoblotting and RT-PCR in the mammary gland of cows; MCT1 and MCT2 have been described as localized at the basolateral membrane of alveolar epithelial cells with the expression of MCT4 at the apical side. Unfortunately, immunostaining of CD147 in cows failed to confirm the cellular localization of MCTs (76). Our in situ hybridization analysis in the murine mammary gland could not detect any significant mRNA expression of MCT2 or MCT4.…”

Lactate-H+Transport Is a Significant Component of the In Vivo Corneal Endothelial Pump

“…31 Nevertheless, some studies show that MCT4 can localize to the apical membranes in certain tissues. 32,33 Even in the same organ (e.g., small and large intestine), the expression profile of MCT4 varies depending on the region. 33 It has also been reported that MCT expression in a tissue can vary among different animal species.…”

Histological characterization of orphan transporter MCT14 (SLC16A14) shows abundant expression in mouse CNS and kidney

“…As for MCT14, its substrate profile is still unknown and the expression data are limited. MCT14 has been found in bovine mammary gland, in the gastrointestinal tracts of cattle and the mammary glands of lactating cows [ 21 – 23 ], but there is no detailed immunohistochemical analysis of MCT14 expression in mouse brain.…”