Observations on the Multiple Nature of the “Rat Filtrate Factor.”

Abstract

The fitrate factor for rats is that material present in fuller's earth filtrates of liver extract which promotes the growth of rats maintained on a basal diet of only pure chemicals. It has been generally assumed that the growth response is due to the presence of one vitamin in the filtrate, although there have been some dissenters from this view. 1 , 2 It has recently been shown 3 , 4 , 5 that relatively pure preparations of the chick antidermatitis factor or pantothenic acid will produce a good growth response in rats in the classical filtrate factor assay. Hence the question arises as to whether pantothenic acid is to be identified with the “rat filtrate factor.”

Results of the present investigation show clearly that there are other unknown growth factors for the rat. Pantothenic acid promotes growth in a filtrate-factor-deficient animal only for a relatively short period. It appears that a growth response is obtained only because the young rat has a sufficient store of other growth factors to meet his needs for the relatively short duration of the usual filtrate factor assay. If young male rats are fed a synthetic ration for 4-6 weeks, they will no longer show a growth response when pantothenic acid is subsequently supplied to them. They still respond dramatically when certain liver concentrates in addition to pantothenic acid are added. If the pantothenic acid is added after 3 weeks, rather than after 4-6 weeks, on the synthetic ration, about half of the animals will grow for a week or 2 and then the growth again ceases. Addition of even 200 mg per day of pantothenic acid fails to produce a response, whereas 50 mg will produce good growth in the usual filtrate factor assay.