Cardiac atrial factor--an endogenous diuretic?

An extract of rat heart atria causes a saluresis in bioassay rats. When organic acid secretion in the proximal tubule was blocked by probenecid, the saluretic response to the extract was significantly reduced. Similarly, the natriuretic response to acute hypervolemia was reduced by probenecid administration. The data indicate that the atrial natriuretic factor, like the "loop" diuretic drugs, requires proximal tubular secretion for maximal renal activity. Furthermore, the factor may play a role in the renal response to acute blood volume expansion.