LETTERS AND COMMENTS ADBENOGORTICOTROPHIC HORMONE AND ERYTHROPOIETIN To the Editor: In the article entitled "Hypo- thalamic Control of Red Cell Production " by

the tissue tension of oxygen in the kidneys themselves controls the rate of red cell produc-tion. However, Seip, Halvorsen, Andersen, and Kaada (1) and Halvorsen (2) have reported that hypothalamic stimulation increases the rate of red cell production and that hypothalamic ablation interferes with normal erythropoietic response to hypoxia. Richards and Sayers (3) have reported that in rats relatively large amounts of injected adrenocorticotropic hor-mone (ACTH) accumulate in the kidneys, and Marks, Garber, and McCoy (4) indicated that the juxtaglomerular apparatus responds quickly to ACTH. Recent studies (5) have shown that ACTH stimulates the renal juxtaglomerular apparatus, directly increasing renin release in normal subjects and in patients with chromo-phobe adenoma, oat cell carcinomas, and car-cinoma of the breast. Preliminary studies with m I ACTH suggest the possibility that the kid-ney is the principle extra-adrenal site of ACTH action (6). These observations suggest a more attractive hypothesis of the pituitary-kidney axis. The "stress " of hypoxia stimulates in the hypo-thalamus the release of ACTH, which in turn stimulates formation or release or both of ery-thropoietin in the kidneys