RADIOIMMUNOASSAY OF CALRETININ IN THE RAT-BRAIN

A radioimmunoassay was developed for the quantitation of the brain specific calcium binding protein, calretinin, in micropunch samples of the rat brain. The assay was sensitive, capable of detecting 2-100 ng calretinin and was specific in that no significant cross reactivity was observed with calbindin D-28k. Results indicated several brain regions with high concentrations of calretinin including the ventral cochlear nucleus (6400 ng/mg total protein), periventricular nucleus of the thalamus (4400 ng/mg), optic chiasm (3600 ng/mg), medial habenula (3400 ng/mg) and lateral lobules of the cerebellum (3100 ng/mg). Low concentrations of calretinin were found in, for example, the cerebral cortex and hippocampus. The development of this assay will be useful in future studies of experimental and physiological factors influencing calretinin content in the brain.