THE ORIGIN OF FAT FROM PROTEIN IN THE SO-CALLED FATTY METAMORPHOSIS OF PHOSPHORUS POISONING
Authors: Taylor Alonzo Englebert 
Published: June 2004

588.780 grm. of frogs, all of the same sex, of the same comparative approximate weights, taken from the ground about the same time, kept awake and without food for nearly the same time, were divided into equal groups; the one group was poisoned with phosphorus, the other group held as a control. The frogs in the poisoned group lost in dried residue 8.821 grm. or 16.5 per cent of the dried residue of the control group; 1.182 grm. of nitrogen, corresponding to 7.388 of proteid, or 18.45 per cent of the nitrogen and protein in the control frogs; 1.026 grm. of fat, or 22.64 per cent of the fat in the control animals; and 0.261 grm. glycogen, or 13.3 + per cent of the glycogen in the control frogs.
I believe that it is obvious that in these experiments no fats were produced from protein. Mathematically, it is possible to conceive that fats could have been formed but entirely burned up. As previously stated, the carbon in the proteid lost during the poisoning was equivalent to 4.600 grm. of fat, and it is conceivable that these 4.600 grm. of fat were formed, but that they, together with the 1.026 grm. of fat actually lost during the experiments, were burned. In brief, the fat combustion might have been tremendously increased, and masked an actual fat formation. This however is unsupported by evidence, and is highly improbable. It is hard to conceive that in an organism whose katabolic functions were greatly augmented as the result of phosphorus poisoning, in which protein, fat, and glycogen were being burned in excess, the carbon of the protein would first have been converted into fat and then the fat burned as such. I believe the only conclusion which can be drawn from these experiments is that no fat was formed as the result of phosphorus poisoning. Thus the fatty degenerations so-called which occurred in these frogs did not comprehend any formation of fat at all, but simply the deposition of fat.
These results are directly opposite to those of Polimanti. Polimanti apparently did not weigh his animals before the beginning of the experiment, and based his calculations upon the relation of the fat to the dried residue. Obviously his calculation was based upon the assumption that the dried residue of a frog was unaffected by phosphorus poisoning. Polimanti, in declining to base his calculations upon the weight of the animals when dead, states that as water is often increased, such a calculation would be misleading. But since the dried residue may and does vary, calculations based upon it are also misleading, and thus the only proper basis of calculation is the original weight of the frogs before the experimentation. Calculated upon the basis of the dried residue, in my material the percentage of fat in the control animals was 8.48 per cent, in the poisoned animals 7.86 per cent, so that, even upon the basis of Polimanti's incorrect calculation, in my experiments fat was lost in notable quantity.
Just before this study was completed, the publication of Athanasiu, (8) from Pflueger's laboratory, appeared. Operating with a large number of frogs, and under varying conditions, with careful methods and rigid controls, Athanasiu reached the conclusions: that phosphorus poisoning has no effect upon the total quantity of fat in frogs; that it has little effect upon the nitrogen; that it produces a diminution in the quantity of glycogen; and that the fatty degenerations are really fatty infiltrations. While my results agree with those of Athanasiu in the essential point, that no fat was produced by phosphorus poisoning, they differ in that the poisoned frogs, in my experiments, lost fat and protein as well as glycogen, while his frogs lost only glycogen. Since our methods were almost the same, the differences must have resided either in the conditions surrounding the experiments, or in the animals. I do not believe that such differences exist between the Rana fusca and esculenta of Europe and the Rana palustris of America as to explain the differences in our results. These differences I believe may be explained by varying conditions. My animals were kept in a warm cellar, at a temperature of from 18 to 20° C. The period of poisoning with Athanasiu's frogs varied from one to six days; all of my frogs lived over six days, most of them ten or twelve days. Since we know that the katabolic actions of most poisons are greater in prolonged intoxications, it is fair to assume that the time element was the factor in the production of my results.
While it would be unscientific and illogical to state that fat cannot be formed from protein, the fact stands that it has never been shown, either in physiology or pathology, that fats are formed from protein. On the contrary, nearly all of the careful work upon the question has yielded negative results. Not. only has it never been shown that, in fatty degeneration so-called, fat is formed from the cellular protein, but it has never been demonstrated that fat is then formed at all, even from glucosides, etc., substances from which fats may be readily formed.