1. Plasma levels of atrial natriuretic peptide and several other hormones were measured and related to the renal responses to chronic changes in the dietary intake of protein and sodium, alone and in combination. Eight healthy subjects consumed four diets for 1 week: a basal diet containing 140 mmol of sodium/day and 1 g of protein day−1 kg−1, the same diet with isocaloric addition of 1 g of meat protein day−1 kg−1, the basal diet with addition of 170 mmol of sodium chloride/day and the basal diet with both additions.
2. Creatinine clearance was increased significantly both by protein and, to a smaller extent, by sodium. Plasma atrial natriuretic peptide and the urinary excretion of guanosine 3′:5′-cyclic monophosphate were increased significantly by sodium but were not affected by protein. Protein induced a significant rise in plasma glucagon levels, whereas the rise in somatomedin C (insulin-like growth factor I) just failed to reach statistical significance.
3. These findings demonstrate that atrial natriuretic peptide does not mediate chronic protein-induced hyper-filtration, although it may contribute to the renal effects of sodium. Glucagon and somatomedin C (insulin-like growth factor I) may have contributed to chronic protein-induced hyperfiltration.