Polycythemic response in normal adult rats to a nonprotein plasma extract from anemic rabbits.

T HE EXPERIMENTS reported here were suggested by the finsdinsgs its two insdepensdenst linses of insvestigations, onse conscernsed w-ith the erythropoietic responsse to high alt,itudet and the other with the stimulating effect of liver arsd plasma extracts ons the inscorporations of aminso acids ins reticulocytes.2 Drabkins ansd Graybiel’ showed that ins the acclimat.izationi to lowoxygens tenssion, heme (ansd insferenstiallyhemoglobins) synsthesiswasaccelerated. Amonsg the several interpretationss of this fact is the possibility that. erythropoiesis is regulated by a humoral fact.or.35 It was also possible that the factor (or factors) ins liver or plasma which stimulates aminso acid incorporation (proteins synsthesis) ins reticulocytes might he the humoral factor, or at least be related to it. or funsctions like it. The factors found by Borsook aisd his associates2 to stimulate amino acid incorporatiors irsto rabbit reticulocyte proteinss fall insto three categories. Onse coissists of certains aminso acids : histidinse, leucinse, pheisylalansinse, tryptophanse, and valinse. A seconsd they have designated as carbohydrate metabolism factors; these are glucose plus either adensosinsetriphosphate, diphosphopyridinse tsu-