Radioimmunoassay for brain natriuretic peptide (BNP) detection of BNP in canine brain.

We established a highly sensitive and specific radioimmunoassay (RIA) for BNP. Our RIA detected BNP-like immunoreactivity (-LI) in the porcine and canine brains but did not detect BNP-LI in the human, monkey or rat brain. The widespread distribution of BNP-LI was demonstrated both in the porcine and canine brains, with the highest concentration in the medulla oblongata. In contrast, the highest concentration of ANP-LI determined simultaneously was in the midbrain and the olfactory bulb. High performance-gel permeation chromatography coupled with RIA revealed that the major component of BNP-LI was eluted at the position of synthetic BNP with a small molecular weight (3K). These results indicate that the RIA for BNP serves as a useful tool to investigate physiological roles of BNP.