脳のアミノ窒素 第二編 死後変化としてのダイコクネズミ脳遊離アミノ酸量の消長

Quantative changes in the contents of amino-nitrogen, ammonia and individual amino acids during the incubation of fresh rat brain tissue were investigated. Suspensions or slices of the fresh brains were incubated at 37℃ , pH 7.4. Amino-nitrogen was estimated by the modified ninhydrin colorimetric method, and ammonia by the Conway's micro-diffusion analysis. Contents of the individual amino acids and the related compounds of the brain suspensions before and after incubation were also determined. Ion exchange chromatography was employed for this purpose. 1) In the suspensions anaerobically incubated, a rapid increase of amino-nitrogen was found; this increase ceased within about one hour after start of the incubation, showing no further increase during the second hour. The liberation of amino-nitrogen was found to be more rapid in the white matter than in the grey matter of the rabbit brain. 2) In the cases of the brain slices, the increase in amino-nitrogen was a little slower and more protracted, being remarkably disturbed by the addition of glucose. The ammonia contents during incubation showed a relatively slow increase without paralleling with the increase of amino-nitrogen. During the period when the tissue samples were prepared at O℃ ., rapid ammonia formation was recognized while amino-nitrogen remained almost constant. 3) Several amino acids such as serine, glycine, alanine. aspartic acid and γ-aminobutylic acid increased after incubation of one hour, glutathione and N-acetylaspartic acid rather decreased. 4) It appears that this remarkable increase in amino-nitrogen observed during a few hours after death might be due to the effect of "neutral proteinase" as reported by Ansell & Richter.