ADENOSINE-DEAMINASE IN RODENT MEDIAN-EMINENCE - DETECTION BY ANTIBODYTO THE MOUSE ENZYME AND COLOCALIZATION WITH ADENOSINE DEAMINASE-COMPLEXING PROTEIN (CD26)

Adenosine deaminase in the hypothalamic tuberomammillary nucleus and m edian eminence of rat and mouse brains was investigated with two diffe rent antibodies generated against the enzyme derived from either calf or mouse. Both antibodies labelled neurons in the tuberomammillary nuc leus and, as determined in rat, they immunolabelled the same neurons. In the median eminence, immunopositive fibres and terminals were detec ted with anti-mouse adenosine deaminase in both rat and mouse, while n o such staining was seen in either species with antibody against the c alf enzyme. These fibres were most concentrated in the external median eminence, had a more restricted distribution than those containing ei ther galanin or tyrosine hydroxylase and only partially overlapped wit h oxytocin-positive fibres. By electron microscopy, adenosine deaminas e was found in terminals containing both small, clear vesicles with di ameters of 35 to 45 nm and large dense-core vesicles with diameters of 100 to 140 nm. Preadsorption of antibodies with purified enzyme deriv ed from the species against which they were directed eliminated all st aining in rat, while antibody adsorptions across species were less eff ective. Preadsorption of anti-mouse adenosine deaminase antibody with the mouse deaminase led to increased labelling in mouse median eminenc e, suggesting an interaction between tissue components and antibody-li nked enzyme. Tests for the presence of adenosine deaminase-complexing protein (CD26) with an antibody against this protein gave positive lab elling in the median eminence of both species and this labelling was c o-distributed with that seen for adenosine deaminase. These results co nfirm the expression of adenosine deaminase in restricted populations of neurons in rodent brain as revealed with a novel antibody, suggest the presence of a distinct form or localization of the enzyme in the m edian eminence, and raise the possibility that it contributes, perhaps along with CD26, to purinergic regulation of hormone secretion in thi s structure. Copyright (C) 1996 IBRO. Published by Elsevier Science Lt d.