Role of the basal sodium intake in the rats on their response to a natriuretic factor

A previously described natriuretic factor found in urine from man and dogs receiving a high salt diet has been postulated to be of hormonal nature. In order to test this hypothesis, natriuretic factor obtained from a pool of human urine of a standard activity has been injected into rats fed 0.55 (group A), 3.55 (group B), 6.55 (group C) mEq sodium a day as it has been shown that the endogenous activity of this factor depends on the sodium content of the diet. This material induces an increment of the UNaV and FENa in the rats averaging respectively 429.6 +/- 150.1% and 317.5 +/- 71.14% for the rats from group A, 103 +/- 29% and 99.7 +/- 26.25% for the rats from group B, 56.3 +/- 34.4% and 63.2 +/- 35.8% for the rats from group C reflecting the degree of statistical significance observed between the absolute values obtained during the control and experimental periods for each group. In addition, a dose-response curve has been established. Altogether the results suggest the hormonal nature of the natriuretic factor and design the kidney as the target organ. These data allow to define the best conditions under which the rats have to be in order to provide a valuable bioassay for this natriuretic material.