Distribution and molecular forms of brain natriuretic peptide in the central nervous system, heart and peripheral tissue of rat.

The amino acid sequence of rat brain natriuretic peptide (rBNP) precursor has recently been deduced by the cDNA cloning method (1). In the present study, a radioimmunoassay (RIA) system for rBNP was newly established, and regional distribution of rBNP in the central nervous system, heart and other peripheral tissue of rat was investigated. In heart, especially in cardiac atrium, a high concentration of immunoreactive (ir-) rBNP was detected and identified as rBNP-45 and gamma-rBNP. No significant amount of ir-rBNP was found in other tissues examined including the central nervous system. Especially in brain, no ir-rBNP was detected, while ir-rat atrial natriuretic peptide (rANP) was observed at a relatively high concentration. These results demonstrate a sharp contrast between rat and porcine brains in ir-BNP distribution.