In vivo microelectrode monitoring of real-time hydrogen concentration in different tissues of rats after inhaling hydrogen gas

Medical effects of hydrogen have been reported in many studies. Due to difficulties in measuring hydrogen concentration in vivo after intake and high explosive risks of hydrogen, studies about dose-response relationships and tissue concentrations of hydrogen are few. Here, for the first time, we monitored real-time hydrogen concentrations in different tissues in rats including brain, liver, spleen, kidney, thigh muscle, inguinal white adipose tissue, and gonadal white adipose tissue after inhaling different concentrations of hydrogen (4%, 42%, and 67%) using an electrochemical sensor. Hydrogen concentrations in the same tissue showed a dose-dependent response. The equilibrium concentration values were highest in the brain and lowest in the thigh muscle. The saturation and desaturation curves changed more slowly in the thigh muscle and white adipose tissues than in other tissues. These results provide fundamental information for the selection of hydrogen dose applications in basic research and clinical trials. The experiments were approved by the Laboratory Animal Ethics Committee of Shandong First Medical University & Shandong Academy of Medical Sciences (No. 2020-1028) on March 18, 2020.