Changes In Lactate Content Research Articles

Changes in lactate content and monocarboxylate transporter 2 expression in Aβ₂₅₋₃₅-treated rat model of Alzheimer's disease.

Decreased brain energy metabolism is correlated with cognitive impairment in Alzheimer's disease (AD). Accumulating evidence indicates that lactate and monocarboxylate transporters (MCTs) participate in brain energy metabolism. To date, changes in lactate level and expression of MCTs in AD remain unclear. This study was conducted to detect the changes in lactate content and expression of MCT2 in Aβ25-35-treated rat model of AD. Sprague-Dawley rats were randomly divided into control and model groups, which received bilateral intrahippocampal injections of saline and Aβ25-35, respectively. Cognitive functions were detected by Morris water-maze test. Lactate content in the cerebral cortex and hippocampus was measured by absorbance assay. The MCT2 level in the brain was examined by immunohistochemistry and Western blot. Morris water-maze test showed that the model group exhibited impaired learning and memory compared with the control group. Lactate content in the cerebral cortex and hippocampus was decreased in the model group compared with that in the control group. Immunohistochemistry and Western blot showed that the expression of MCT2 in the model group significantly decreased compared with that in the control group. Results indicate that decreased lactate content and downregulated MCT2 expression in the cerebral cortex and hippocampus reflected impaired energy metabolism in the brain, which may participate in the pathologic progression of AD.

Visual stimulation, 1H MR spectroscopy and fMRI of the human visual pathways.

The purpose was to assess changes in lactate content and other brain metabolites under visual stimulation in optical chiasm, optic radiations and occipital cortex using multiple voxel MR spectroscopy (MRS). 1H chemical shift imaging (CSI) examinations of transverse planes centered to include the above structures were performed in four subjects at an echo time of 135 ms. Functional MRI (fMRI) was used to confirm the presence of activity in the visual cortex during the visual stimulation. Spectral maps of optical chiasm were of poor quality due to field disturbances caused by nearby large blood vessels and/or eye movements. The optic radiations and the occipital lobe did not show any significant MR spectral change upon visual stimulation, i.e., the peak areas of inositol, choline, creatine, glutamate and N-acetylaspartate were not affected. Reproducible lactate signals were not observed. fMRI confirmed the presence of strong activations in stimulated visual cortex. Prolonged visual stimulation did not cause significant changes in MR spectra. Any signal observed near the 1.33 ppm resonance frequency of the lactate methyl-group was artifactual, originating from lipid signals from outside the volume of interest (VOI). Previous claims about changes in lactate levels in the visual cortex upon visual stimulation may have been based on such erroneous observations.

Changes in intracellular pH of mouse hippocampal slices responding to hypoxia and/or glucose depletion

Effects of hypoxia and/or glucose depletion on apparent intracellular pH, (pH i) app, were studied in hippocampal slices of mouse brain using the fluorescence pH indicator BCECF (2′, 7′-bis(car☐yethyl)car☐yfluorescein). In the presence of glucose (11 mM), (pH i) app of the CA1 pyramidal cell layer decreased with hypoxia but rapidly recovered with reoxygenation. The response in (pH i) app to hypoxia was consistent with changes in lactate content. By superfusion with a hypoxic and glucose-devoid solution, (pH i) app decreased in the first 5 min, but then increased in two phases: during a 5- to 7-min period and again during the latter period of superfusion. BCECF fluorescence rapidly diminished in this latter period. These changes in (pH i) app could not be explained only by the lactate content in the slices. Some other mechanisms may also regulate the (pH i) app in the slices during and after hypoxia and glucose depletion.

Changes in lactate content in the gills of the mudskippers Periophthalmus chrysospilos and Boleophthalmus boddaerti in response to environmental hypoxia

The gills of Periophthalmus chrysospilos exhibited significantly greater pyruvate kinase and lactate dehydrogenase activities than those of Boleophthalmus boddaerti (P <0.01). Under the control normoxic condition, the branchial lactate content of the former mudskipper was also significantly greater (P < 0.01) than that of the latter. After hypoxic exposure, lactate and alanine accumulated in the gills of P. chrysospilos but not B. boddaerti. Succinate and propionate were not detected in the gills of these two mudskippers under the control and hypoxic conditions.

A 1H-nuclear magnetic resonance study on lactate and intracellular pH in frog muscle.

High resolution proton magnetic resonance spectra of intact frog muscle, obtained by the selective saturation of water signal with 15 min accumulation, showed well-resolved signals from lactate, carnosine, and other compounds. This technique was used to monitor the changes in lactate content and in intracellular pH which was estimated from the chemical shift of carnosine in muscle. The intracellular pH was estimated to be 7.1 in fresh muscles. Under an anaerobic condition, resting muscle showed a gradual increase in lactate content with intracellular acidification. When the anaerobic muscle was electrically stimulated for 5 sec, a transient acceleration of the lactate production and the intracellular acidification was observed. The intracellular buffer value was estimated to be 27 mEq/(pH X kg muscle), based on the pH change due to the increase in lactate content.