Journal of Neuroscience, Vol 6, 2707-2714, Copyright © 1986 by Society for Neuroscience
Distribution of adenosine deaminase activity in rat brain and spinal cord
JD Geiger and JI Nagy
The activity of adenosine deaminase (ADA) was measured in 62 discrete
regions of the CNS, and in some autonomic and sensory ganglia, peripheral
nerves, and peripheral tissues of the rat using an automated high-pressure
liquid chromatography (HPLC) method. The formation of inosine and
hypoxanthine as a measure of ADA activity in homogenates of brain was
optimal at pH 7.0, linear for up to 60 min at 37 degrees C using 500 microM
adenosine as substrate, and linear with protein concentrations ranging from
0.05 to 0.8 mg. The Km and Vmax values for ADA activity in homogenates of
whole brain were 47 microM and 107 nmol/mg protein/30 min, respectively.
Among the CNS regions examined, the highest activity was found in posterior
hypothalamic magnocellular nuclei and the lowest in hippocampus. In
general, spinal cord contained relatively low levels of ADA activity, with
that in dorsal cord approximately 40% higher than ventral cord. In the
periphery, parasympathetic ganglia contained higher levels of ADA than
sensory ganglia and brain. Most peripheral tissues--including adrenal
gland, lung, liver, and anterior and posterior pituitary--exhibited
activity comparable to levels in the posterior hypothalamus. ADA activity
in thymus was about 10 times higher than any other tissue examined. The
uneven distribution of ADA activity in the rat CNS corresponds well with
the immunohistochemical localization of this enzyme in discrete neural
systems of this species. Structures that contain high ADA activity exhibit
intense ADA immunostaining of neuronal perikarya and/or fibers.(ABSTRACT
TRUNCATED AT 250 WORDS)