CHANNON AND MARRIAN [1926] examined the unsaponifiable fraction of pig liver primarily with a view to investigating the possible presence in liver of the unsaturated hydrocarbon squalene. Their results showed that, although squalene was not present, pig liver contained a highly unsaturated hydrocarbon of apparently very high molecular weight, and some evidence was obtained that this hydrocarbon was of terpenoid nature. The presence of the hydrocarbon was deduced from the ready preparation of an insoluble bromide and of a hydrochloride from fractions of the unsaponifiable matter into which the more unsaturated constituents had been concentrated. Analysis of the former compound showed that it was the bromide of an unsaturated hydrocarbon. The hydrochloride however was contaminated by an impurity which could not be removed and the mean values for the C, H and Cl analyses totalled no more than 98-71 %.The investigation of the unsaturated hydrocarbon did not progress further, because it could not be obtained in pure form; concentrates of it decomposed when distilled in.vacuo, and regeneration by dehalogenation of its halogen compounds was unsatisfactory. Further, deductions as to the molecular formula of the substance from consideration of the analyses of the halogen compounds could not be made, for the molecular weight of the hydrocarbon was unknown, nor could those of the bromide and hydrochloride be determined on account of their properties. The great advances which have been made in knowledge of the chemical nature of the higher terpenes in the last few years and the increasing realisation of the biochemical importance of these substances suggested that further investigation of the liver compound was desirable. It seemed not inconceivable that this compound might be concerned with the metabolism of carotene and vitamin A, or possibly with that of cholesterol, for the feeding of squalene to rats causes a noteworthy increase in the amount of cholesterol in the liver [Channon, 1926]. This paper therefore contains an account of attempts to obtain the unsaturated hydrocarbon of mammalian liver in pure form as a preliminary to its chemical investigation. Sufficient progress has been made to lead us to publish the results so far obtained, for further advance cannot be made until more material is available, the preparation of which will entail a considerable delay. EXPERIMENTAL.Preparation of the unsaponiftable fraction.Pig liver, having been shown to be richer in the hydrocarbon than that of the other mammals investigated, was again used as the starting material. The method adopted for the preparation of the unsaponifiable matter was essentially that used by Channon and Marrian [1926]. The pig liver was obtained from the
RATS fed on low protein diets of high fat content with or without small amounts of cholesterol develop intensely fatty livers; when caseinogen is used as the dietary protein, the degree of fat infiltration diminishes on increasing the amount of this protein present in the diet, irrespective of any action of choline [Channon & Wilkinson, 1935; Beeston et al. 1935]. Further work has shown that a daily intake of 1 g. caseinogen has an effect equivalent to that of 7-8 mg. choline [Beeston & Channon, 1935; Beeston et al. 1936]. Best et al. [1936] obtained similar results regarding this extensive action of caseinogen on liver fat deposition in preventive experiments. While we are continuing our studies of the action of pure amino-acids as one method of elucidating the mechanism of this action of caseinogen [Beeston & Channon, 1936; Channon et al. 1938], information as to the relative lipotropic actions of other proteins is desirable for two reasons. Firstly, it would enable the intensity of action of different proteins to be studied in relation to their amino-acid composition, and perhaps provide evidence of value from this point of view; secondly, it is important to determine which proteins are most satisfactory from the experimental point of view. Diets low in protein tend to cause weight losses even in the short term studies often used in this type of work, and a balance has to be struck between the desirable high fat percentage in the liver and ensuing weight losses. The work described in this paper is, therefore, a study of the actions of a number of plant and animal proteins in preventing fat deposition in the liver, caseinogen being used as the standard. EXPERIMENTAL Preparation of the proteins Edestin was crystallized from 5 % NaCl extracts of hempseed, washed twice with water, twice with alcohol and with ether; the dried powder was extracted twice with hot alcobol and with ether. Yield 75-80 g./kg. hempseed. Fibrin obtained from the slaughterhouse was water-washed until colourless, and dried in alcohol; the powdered product was extracted with water, cold alcohol, hot alcohol and finally with ether. Gliadin. Repeated extraction with 73 % alcohol (3, 3 and 2 1.) of wheat gluten flour (1 kg.), concentration in vacuo of the extracts and cooling in the refrigerator gave a jelly of gliadin, which was dehydrated by successive treatments with acetone; the finely ground product was extracted with cold absolute alcohol and with ether. Yield 275-290 g./kg. gluten flour. Zein. Maize gluten meal (1 kg.) was extracted repeatedly with hot 80 % alcohol (4, 2 and 2 1.), the extract concentrated to 2-5 1., and mixed with 2-5 1. of ether. The gelatinous precipitate was dissolved in warm 90 % alcohol and (976)
IN one experiment of a series in which study was made of the effect of choline in preventing the accumulation and accelerating the removal of fat in the liver of the rat, Best and Huntsman [1935] observed that, when rats which already had a liver fat percentage of 10-13-5 were transferred to a diet of pure sucrose, the liver fat was further increased by some 8 % during the course of 6 days. In a comparable experiment in which the transfer was made to a diet containing 80 /o of sucrose with 20 % of caseinogen, this increase in liver fat did not occur.Assuming a daily food intake of 10 g. per animal, this experiment suggested that 2 g. of caseinogen had prevented an 8 % rise in the fat of a liver which was already loaded with fat. Best and Huntsman were unable to decide at that time whether this action of caseinogen was due to the fraction of a mg. of choline present in the diet and they pointed out in further possible explanation. of this result that caseinogen might give rise to betaines during its metabolism, since betaine itself was shown to be lipotropically active by Best and Huntsman [1932]. At the same time Channon and Wilkinson [1935] were investigating the production of fatty livers in normal animals on synthetic diets, because they had failed to obtain such livers by the use of the diet of mixed grain and 40 % fat originally used by the Toronto workers. Various considerations discussed by them suggested that the amount of the protein present in the diet might be a governing factor in fatty liver production and they concluded from a series of experiments that the amount of fat appearing in the liver was controlled by the amount of protein in the diet, irrespective, however, of any action of choline. In a criticism of these results, Best et al. [1935] drew attention to their experiment mentioned above ax4d stated that the results of their more recent unpublished experiments suggested that 1 g. of the caseinogen used by them had no greater effect on liver fat than did 0*5 mg. of choline. They further stated that, whilst the lipotropic effect of caseinogen was not to be underestimated, in their opinion the effect could be accounted for if the protein contained 0-2 or 0 3 % of choline, betaine or other substances with a similar action.Meanwhile Beeston et al. [1935] had applied their previous findings on this protein effect to a further extensive study of the "cholesterol" fatty liver with results which amply confirmed their original conclusion that the caseinogen present in the diet controlled the amount of glyceride appearing in the liver, irrespective of any action of choline. As typical of this powerful action of the caseinogen may be mentioned an experiment in which the amount of glyceride in the livers of a group of animals was reduced by 18-69 % by the extra daily 1 The substance of this paper was reported at a
AlLAN et al. [1924] reported that depancreatized dogs receiving adequate amounts of insulin and maintained on a diet of lean meat, sucrose and bone ash did not survive for periods of more than a few months. They also observed that the symptoms of failure of liver function due to fat infiltration of the liver found in such animals, could be prevented by adding raw pancreas to the diet. They suggested, therefore, that the pancreas might possibly produce an internal secretion necessary for the physiological integrity of the liver. The subsequent discoveries of Hershey [1930] that lecithin could successfully replace raw pancreas in the diet of depancreatized dogs, and of Best & Huntsman [1932] that choline and betaine could prevent and cure fatty infiltration in the livers of rats fed on high fat diets have been extended in many directions. So far as we are aware, however, no proof has yet been advanced that the active agent of the pancreas is, in fact, choline, and particular interest therefore attaches to the claims of Dragstedt and his colleagues [Dragstedt et al. 1936, 1, 2] that raw pancreas contains an active substance other than choline and that this substance, to which they give the name " lipocaic " may be concentrated in dilute alcoholic extracts of the tissue. The work described in this paper was undertaken in an attempt to extend these findings to the dietary fatty liver of the rat, which lends itself to more accurate experimentation than that of the depancreatized dog.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.