The effect of volume expansion on atrial natriuretic peptide and cyclic guanosine monophosphate levels in young and aged subjects.

The relationship between atrial natriuretic peptide (ANP) and age was studied. In elderly subjects (65 to 84 years) higher basal ANP levels were found as compared with those found in young subjects (21 to 23 years). Volume loading (750 mL 0.9% NaCl in 60 minutes) increased ANP levels only in the aged group, and plasma renin activity decreased only in the young subjects. Plasma aldosterone levels did not change. Basal cyclic guanosine monophosphate values did not differ in either group, and rose to a similar extent during volume loading. High pressure liquid chromatography analysis did not suggest different molecular forms of immunoreactive ANP in elderly subjects. The main circulating component both basal and after stimulation corresponds to the (99-126)hANP form.