Summary
A study was conducted in order to contribute to the methodology and topochemical localization of amino acid dehydrogenases in mammals; Nitro-BT, Tetra-Nitro-BT and phenazine methosulphate were used in the tests. Under anaerobic incubation conditions varying amounts of some α-amino acids (dextrorotators) are oxidized in the mammalian kidney. The positive test result is regarded as the manifestation of a d-amino acid dehydrogenase activity. The investigation reveals that the kidney of carnivores (cat, dog, mink) shows the highest d-AAD-activity. However, this activity is histochemically not detectable in the kidney of genuine herbivores (guinea pig, rabbit, cattle). Rat, mouse, pig, and sheep take an intermediate position. In most of the species investigated the oxidative deamination of the d-amino acids takes place in the pars recta (renal cortex). In humans and sheep, however, the entire renal cortex gives positive results. The reaction is negative in the liver of most of the species tested.
Out of the l-amino acids, tested in the course of the investigation, it is only l-proline that gives a positive result on kidney sections. In contrast to the findings concerning d-AAD activity, the formazan deposits are seen in the pars convoluta. In all probability this activity can bei regarded as a specific proline-dehydrogenase.