Sensitive immunoassay for rat parvalbumin: tissue distribution and developmental changes.

A sensitive enzyme immunoassay for measurements of rat parvalbumin was established using antibodies raised in rabbits with parvalbumin purified from skeletal muscles. Antibodies in the antiserum were purified with a parvalbumin-coupled Sepharose column. The sandwich-type immunoassay system for parvalbumin was composed of polystyrene balls with immobilized purified antibodies and the same antibodies labeled with beta-D-galactosidase from Escherichia coli. The assay was highly sensitive and the minimum detection limit was 1 pg parvalbumin/tube. The assay did not cross-react with other calcium binding proteins, including human S-100a0 and S-100b proteins, rat 28-kDa calbindin-D, and bovine calmodulin. High concentrations of parvalbumin were observed in the skeletal muscles, especially in those composed of fast-twitch fibers, and in the diaphragm and tongue, but not in heart muscle. A relatively high concentration was estimated in the central nervous tissue. Parvalbumin was detected in the cerebral cortex and cerebellum of gestational 15-day fetuses. However, the levels of parvalbumin in the muscle tissues and central nervous tissue were very low in rats before 1 week of age. Thereafter, they increased sharply, reaching the adult levels by 5 weeks in most of the tissues. Parvalbumin concentrations in adult rat soleus muscle increased less than 20-fold within 10 days after transection of the ipsilateral sciatic nerve, while the concentrations in the extensor digitorum longus muscle did not change in the same period.