Hormonal actions of the heart and of lungs on the isolated kidney.

1. An hormonal influence of the heart on the isolated kidney has been demonstrated by insertion of hearts into pump-oxygenator circuits during renal perfusions.2. This hormone is a steroid which is secreted from the heart into the cardiac venous blood in response to reduction in venous input. The steroid is extractable from heart muscle.3. The actions of the cardiac steroid resemble those of aldosterone but are of shorter latency. Renal blood flow (R.B.F.) and glomerular filtration rate (G.F.R.) rise; urine flow, Na-concentration and Na/K decrease.4. An hormonal influence of lungs on the isolated kidney is also demonstrated. This hormone is not a steroid. It is antidiuretic and Na-retaining: the concentration of urinary Na rises: Na/K remains unchanged.