Abstract
Purpose::
The cornea is a very glycolytic tissue and produces a significant amount of lactic acid which needs to be removed in order to maintain balanced osmolarity. The purpose of this study is to determine the presence of monocarboxylate transporters (MCTs) in the corneal endothelium and its role in transporting lactic acid.
Methods::
MCT isoforms 1-4 total RNA were screened by RT-PCR followed by sequencing. MCT 1-4 western blots were also performed. Immunofluorescent screening is in progress to localize the MCT proteins. To examine its physiological function, bovine corneal endothelial cells cultured on permeable anodiscs were loaded with the intracellular pH sensitive fluorescent dye with 2’,7’-bis(2-carboxyethl)-5(6)-carboxyfluorescein acetoxy-methylester (BCECF-am). The cells were exposed to various concentration of lactate (10, 20, 30, 40 or 50 mM) on either the basolateral or the apical surface. The rate of pHi changes was measured.
Results::
Sequencing of MCT PCR amplicons and Western blot confirmed the presence of MCT 1, 2, and 4 in bovine corneal endothelium. BCECF-am measurements showed a decrease in pH following lactate exposure to the basal and apical surface in a dose dependent manner and exhibited saturation kinetics, suggesting that lactate flux into endothelial cells was via a protein mediated transport process.
Conclusions::
Preliminary data shows that MCTs 1, 2, and 4 are present. Physiology data suggest that MCTs transport lactic acid across both apical and basolateral surfaces of the bovine corneal endothelium.
Keywords: cornea: endothelium • ion transporters • cornea: basic science