Atrial natriuretic factor in inbred Dahl salt-sensitive and salt-resistant rats

The atria of adult Dahl salt-sensitive (S) rats contain more atrial natriuretic factor (ANF) than the atria of adult Dahl salt-resistant (R) rats by both radio-immunoassay and bioassay. This strain difference is not present between 1 and 15 days of age but is present at 30 days of age and persists throughout adulthood. The precursors of ANF immunoprecipitated from in vitro translations of atrial messenger RNA (mRNA) had the same molecular weight in S and R strains. Hypothalamic levels of ANF were similar in S and R. Kidneys of weanling S rats were hyporesponsive to ANF compared with R, but as the S rats became hypertensive with age the situation was reversed, with S rats being hyperresponsive to ANF. Aortic vascular responses to ANF were identical in S and R rats. Plasma ANF was similar in S and R rats on low-salt diet, but increased markedly in S, but not R, on high-salt diet. It is concluded that any genetic defect in the ANF system in Dahl S rats is most likely to involve the kidney response to ANF, and that high plasma ANF in salt-fed rats may be a consequence of volume expansion and hypertension.