Shinya Matsumura

Oral administration of γ-aminobutyric acid affects heat production in a hot environment in resting humans

BackgroundCentral administration of γ-amino butyric acid (GABA) induces lower body temperature in animals in hot ambient air. However, it is still unknown whether oral GABA administration affects temperature regulation at rest in a hot environment in humans. Therefore, in the present study, we specifically hypothesized that systemic administration of GABA in humans would induce hypothermia in a hot environment and that this response would be observed in association with decreased heat production.MethodsEight male participants drank a 200-ml sports drink with 1 g of GABA (trial G) or without GABA (trial C), then rested for 30 minutes in a sitting position in a hot environment (ambient air temperature 33°C, relative humidity 50%).ResultsWe found that changes in esophageal temperature from before drinking the sports drink were lower in trial G than in trial C (-0.046 ± 0.079°C vs 0.001 ± 0.063°C; P < 0.05), with lower heat production calculated by oxygen consumption (41 ± 5 W/m2 vs 47 ± 8 W/m2; P < 0.05).ConclusionsIn this study, we have demonstrated that a single oral administration of GABA induced a larger decrease in body core temperature compared to a control condition during rest in a hot environment and that this response was concomitant with a decrease in total heat production.

Combined effects of lead and edta on Na+,K+‐ATPase activity of erythrocyte membranes

Erythrocyte Na+,K+-ATPase activity increased significantly in lead workers of a lead refining factory when measured with EDTA and compared to the controls without EDTA. The enzyme activity measured with EDTA increased in the following order: controls less than office workers in a lead refining factory less than lead workers. A positive correlation existed between blood lead and enzyme activity with EDTA (r = 0.380, p less than 0.10), and the activity without EDTA (r = 0.398, p less than 0.05). A negative correlation was found between sodium in erythrocytes and enzyme activity with EDTA (r = -0.437, p less than 0.05), and the activity without EDTA (r = -0.416). But no relationship was observed between enzyme activities and potassium in erythrocytes. A positive correlation between enzyme activity with EDTA and that without EDTA was observed (r = 0.452, p less than 0.05). With addition of lead to fragments of erythrocyte membranes, a significant decrease occurred in the activity of the enzyme without EDTA, whereas no change was observed with EDTA. No significant change occurred in the enzyme activity with and without EDTA upon addition of lead to blood. The maximum level of lead in membrane fragments (lead combined with membranes) of workers exposed to lead was 0.60 microgram/mg protein, and that in the experiment of addition to blood was 7.0 micrograms/mg protein.