Natriuretic activity of extracts obtained from hearts of different species and from various rat tissues

Heart tissue extracts from different species as well as extracts obtained from various rat tissues were tested for natriuretic activity in the nondiuretic bioassay rat. Natriuretic activity was found restricted to heart tissues. Atrial but not ventricular extracts of mammals and both atrial and ventricular extracts in the frog displayed natriuretic activity. Specific natriuretic activity values were highest in the atria of small rodents. It is concluded that the distribution and relative content of natriuretic activity of cardiac tissues from different species approximately parallels the distribution and relative abundance of specific heart granules.