Alterations of H-and M-isozymes of Lactic Dehydrogenase(LDH) were observed in the various tissues after´ exposing the rats to 59ppm and 25Oppm of sulfur dioxide. These isozymes of the respective tissue were separated by Diethlaminoethyl (DEAE)-cellulose from the tissue homogenates of brain, lung and muscle, presenting the activities by rate of reduction of nicotiiiamide-adenine-dinucleotide (NAD+).
Pure LDH and the caenzyma (NAD+) were directly treated with sulfur dioxide in vitro in order to find out the direct to sulfur dioxide on LDH and NAD} and the results were as follows.
1. In the normal´ tissues, the H-isozyme activity was ´dominant in the brain and heart, and the M-isozyme in the muscle.
2. In the lung tissue of normal rats, there was no difference between the activity of H-and M-type. of LDH.
3. When rats inhale sulfur dioxide gas in concentration of 50ppm and 250ppm, it appeared that the H-type tend to be suppressed in aerobic tissues and the M-type in anaerobic tissues.
4. In the lung tissue exposed to sulfur dioxide, both the LDH activities were suppressed.
5. It seems that LDH and the coenzyme (NAD+) are not directly affected by exposing in sulfur dioxide gas.
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