1. Extracts of kidneys have been prepared containing a substance which lowers arterial blood pressure for prolonged periods in patients with essential and malignant hypertension, and in hypertensive dogs and rats.
2. Several different chemical procedures are proposed for the preparation of the extract. The best one has not been decided upon.
3. The quantity of original fresh whole kidney required to yield enough extract to lower blood pressure from hypertensive levels (200 mm. Hg mean pressure) to normal levels is roughly 600 to 900 gm. in dogs within 4 to 8 days. In hypertensive patients the yield from 700 to 1000 gm. daily for several weeks may be necessary.
4. Lowering of the blood pressure too rapidly in animals results in a shock syndrome which may be fatal. If overdosage is avoided, no appreciable rise in blood urea nitrogen occurs, nor do other signs of toxicity appear.
5. Lowering of blood pressure to nearly normal levels has been accomplished in 60 hypertensive dogs, and in some of these it has been allowed to rise and was again reduced as many as five times. Similar results have been obtained with hypertensive rats.
6. Six patients with essential hypertension have been treated resulting in prolonged reduction of blood pressure. Clinically the patients appear improved.
7. Five patients with malignant hypertension have been treated, with reduction of the blood pressure in all instances. One patient was treated despite urea clearance of 5 per cent of normal. His blood pressure was sharply reduced, but death in uremia occurred. The second patient also exhibited sharp reduction of pressure and died after treatment was discontinued. The other three are much improved after treatment, as indicated by increase in vision and mental activity, loss of dyspnea, improvement in the electrocardiogram, etc.
8. The length of time the blood pressure remains lowered varies greatly in both animals and man. The trend is usually upwards after discontinuing treatment for 4 to 6 days.
9. Increasing experience with this treatment suggests that it is of value in the management of hypertension, but it is yet in the experimental stage.