THE BIOLOGICAL ESTIMATION OF PYRIDOXINE (VITAMIN Be)*

Since the discovery of vitamin Bs, several biological assay procedures for this factor have been proposed (Gyorgy (1) ; Lunde and Kringstad (2); Wilson and Roy (3) ; Schneider et al. (4) ; Halliday and Evans (5) ; Edgar, El Sadr, and Macrae (6) ; Dimick and Schreffler (7); Reedman et al. (8)). These methods, with the exception of that of Edgar et al., are based upon the cure of acrodynia produced on a vitamin Bs-deficient ration or upon a combination of growth and the cure of acrodynia of vitamin Bedepleted rats. Edgar et al. propose an assay based on the growth response alone. In light of the fact that factors other than vitamin Be are concerned in the production and alleviation of dermatitis in the rat, methods involving the curing of dermatitis present difficulties in technique and interpretation (Birch (9) ; Schneider et al. (10)). Furthermore some workers have not been able to produce the dermatitis consistently (Dann (11)). The method described here is based entirely upon the growth response of vitamin Be-depleted rats supplemented either with synthetic pyridoxine or the substance to be assayed. Two rations are described. In Ration I a fullers’ earth filtrate of a butanol extract of 1: 20 liver concentrate powder is used to supply pantothenic acid and unidentified factors necessary for the rat. When synthetic pantothenic acid became available, Ration II was devised in which synthetic pantothenic acid and 0.25 per cent of