Tissue distribution and developmental profiles of immunoreactive alpha B crystallin in the rat determined with a sensitive immunoassay system

In order to determine the quantitative distribution of alpha B crystallin (alpha B) in non-lenticular tissues, we have established a sensitive immunoassay system for specific measurement of alpha B. Antisera were raised in rabbits by injecting alpha B purified from bovine lenses, or C-terminal decapeptide (KPAVTAAPKK) of alpha B (alpha Bpep). The antibodies to alpha B and alpha Bpep were purified by the use of alpha B-coupled Sepharose column. The F(ab')2 fragments of antibody IgG to alpha B were immobilized on polystyrene balls and the Fab' fragments of antibody IgG to alpha Bpep were labeled with beta-D-galactosidase from Escherichia coli. The sandwich-type enzyme immunoassay consisted of the above two antibodies was sensitive, and the minimum detection limit of the assay was 10 pg alpha B without any crossreactivity with alpha A. By using the assay method, it is revealed that the alpha B was distributed in most of the tissues examined. Among the non-lenticular tissues, alpha B was present at high levels in the heart and striated muscles, especially in the soleus muscle, and kidney. High levels of alpha B in the muscle tissues were also seen in various animals. Developmental increases of alpha B in rat muscle tissues and kidney were observed from 16 days of gestational age to 1 or 5 weeks of postnatal age. In contrast, the alpha B in the brain kept a low level during the same period. After 5 weeks of age, alpha B concentrations in the brain increased sharply, reaching the adult levels at 9 weeks of age. Immunohistochemical staining with anti-alpha Bpep revealed that alpha B was positive not only in glial cells, in the central nervous tissues, but also in some neurons of spinal cord, brainstem, hippocampus, and olfactory bulb. Spermatocytes in the testis were also immunopositive for alpha B.