Sulphur metabolism. I. The absorption and excretion of flowers of sulphur

Abstract

1. Experiments have been conducted with rats and sheep to determine the absorption and excretion of flowers of sulphur, and it was found that both processes took place at a relatively slow rate. 2. The steps in the metabolism of sulphur were its reduction in the digestive tract to hydrogen sulphide in which form it was absorbed. The sulphide absorbed as such was subsequently oxidised to sulphate and excreted in the urine as inorganic sulphates. 3. The excretion of the inorganic sulphates took place very slowly, because 8 days after the discontinuation of sulphur-feeding (Ration IV, Table I, containing- 1 per cent. of elementary sulphur) the inorganic sulphate in the urine of rats was still 1.6 times as high as compared with that during the pre-sulphur period. In the case of sheep, it took 11 to 12 days, after the retraction of sulphur (5 gm. daily per animal) from the ration, for the inorganic sulphate to return to its normal level. 4. The slow excretion of sulphates in the urine was not only due to the storage of sulphur in the animal body but in part also to the long retention of sulphur in the digestive tract whence some was still absorbed before all of it was swept out of the digestive tract with the food residues. 5. The rise in the excretion of total sulphur in the urine during the sulphur period above that during the pre-sulphur one, with due allowance for a transition period, served as an index of the absorption of elementary sulphur, and when based on this assumption, the following absorption values were obtained:- 24•6, 44•6 and 20•9 per cent. by rats on mixed Rations II, III and IV (Table 1) containing 0•5 per cent., 1 per cent. and 1 per cent. of added flowers of sulphur, respectively. It will be seen that when the basal ration was high in easily available "food-sulphur" (Rations II and IV) the absorption of elementary sulphur was low, whereas when the absorption of "food-sulphur" was low (Ration III) that of the elementary sulphur was high. 6. Apparently the level at which the administration of elementary sulphur will commence to show toxic effects, will be controlled by the concentration of easily available "food-sulphur" in the basal ration. The larger the concentration of "food-sulphur" the higher will be the toxic level of elementary sulphur, and vice versa. 7. The absorption of elementary sulphur, as determined by the Bergeim method on a protein-free diet (Ration I, Table I) containing 1 per cent. of sulphur, was found to be about 38 per cent. This slightly lower value, as compared with that obtained on the low protein Ration III, containing 1 per cent. of elementary sulphur, might probably be explained on the grounds of the incompleteness of the protein-free ration from a nutritional standpoint, and the subsequent marked state of constitutional disorder. 8. The absorption of elementary sulphur by sheep when ingested with the basal ration (200 gm. cut up lucerne hay, 400 gm. crushed yellow maize and 4 gm. NaCl), to the extent of 5 gm. per animal per day, was found to be 28•13 per cent. 9. At this level the feeding• of sulphur had no deleterious effect on sheep, whereas under the conditions of the rat experiments, the addition of 1 per cent. of sulphur to the basal rations showed definite toxic symptoms within a relatively short period of time. 10. The symptoms were anorexia and subsequent cachexia during the sulphur periods, and furthermore, an impairment of the normal physiological functions of the urinary excretory system. 11. The physiological principles underlying the metabolism of elementary sulphur would seem to be similar in rats and sheep.