Immunoreactive atrial natriuretic peptide in the guinea pig spleen.

The presence of immunoreactive ANP precursor-like material in the guinea pig spleen is suggested. This is based on the following experimental evidence: An acidic extract of guinea pig spleen analysed by Sephadex G-50 gelfiltration contained 4.6 pmol/g wet tissue immunoreactive atrial natriuretic peptide (IR-ANP), coeluting with the 15 kDa synthetic ANP (2-126). Gelfiltrated IR-ANP material was further submitted to reverse phase high performance liquid chromatography and monitored by radioimmunoassay employing two antisera. One antiserum recognizes the C-terminal of ANP (1-126), the second is directed against the N-terminal sequence. Both antisera revealed material eluting with synthetic ANP (2-126). Furthermore, immunohistochemical analysis suggests this ANP-like material to be localized mainly at the periphery of the white pulp of the spleen. These findings link ANP with the immune system.