Species‐specific distribution of aromatic L‐amino acid decarboxylase in the rodent adrenal gland, cerebellum, and olfactory bulb

Abstract

Aromatic L‐amino acid decarboxylase (AADC), the enzyme that converts L‐dopa to dopamine, displayed species‐specific differences in both activity and immunoreactivity in the cerebellum, olfactory bulb, and adrenal glands of three rodent species, the hamster, rat, and mouse. Specifically, in the hamster but not the rat or mouse, AADC immunoreactive cells were observed in the cerebellum and adrenal cortex. The unusual distribution of the enzyme was confirmed biochemically. AADC activity was greater in the adrenal gland and the cerebellum in the hamster than in the mouse or rat. In addition, by Western blot analysis, one band of appropriate molecular weight was observed both in the hamster adrenal gland and cerebellum. The rat adrenal gland displayed a similar immunoreactive protein on the Western blot; however, the protein could not be detected in the rat cerebellum by the technique utilized. Tyrosine hydroxylase (TH) immunoreactivity in these same tissues did not differ among the species. In the main olfactory bulb of the mouse, juxtaglomerular cells exhibited very limited immunoreactivity for AADC, but TH‐immunoreactivity in these cells was robust. In contrast, juxtaglomerular cells in the rat displayed a similar intensity of immunostaining for both AADC and TH. AADC activity in the mouse, consistent with the reduced immunostaining for the enzyme, was 50% of that in the rat and the hamster. These data demonstrate that AADC protein, which is contained in cells of diverse function, also displays qualitative and quantitative species specific variations in both distribution and amount.