Presence of atrial natriuretic polypeptide in the pulmonary vein and vena cava

Striated muscle cells and storage granules observed in the atria were found in main branches of the pulmonary veins and superior and inferior venae cavae of the rat, pig, and ox. The presence of atrial natriuretic polypeptide (ANP) in these veins was examined by reverse-phase high-performance liquid chromatography coupled with a radioimmunoassay for ANP. The veins contained 0.6 to 8.0 ng ANP/mg wet tissue with the major molecular form being gamma-ANP. ANP was detected in the peripheral lung tissue in a small quantity, but was not detected in the pulmonary artery. The identification of gamma-ANP and storage granules stained with an anti-ANP antiserum in the pulmonary vein and vena cava suggest that the veins may participate in regulating volume status, blood pressure, and cardiovascular homeostasis through the release of ANP.