Atrial natriuretic factor: atrial conversion of high to low molecular weight forms

The atrial natriuretic factor elutes by gel filtration in high and low molecular weight fractions. Extraction and elution of rat atria in 1.0 M acetic acid yielded a predominance of the high molecular weight form(s); whereas when these procedures were carried out in 0.1 M acetic acid, there was a predominance of the low molecular weight forms. When partially purified high molecular weight natriuretic activity was eluted in 0.1 M acetic acid, the high molecular weight form(s) remained intact. When partially purified high molecular weight natriuretic activity was mixed with crude atrial extract in 0.1 M acetic acid, there was an apparent conversion to the low molecular weight forms. Extraction of rat atria in boiling 0.1 M acetic acid blocked this conversion. It is concluded that rat atria contain a heat labile factor that converts high molecular weight natriuretic activity to the low molecular weight forms.