Physiological Action

Oxidation And Nutrition

How far alkalies, as such, contribute to oxidation, has long been a question of interest, and it is one of great practical importance. Organic substances, such as bile and haematin, when exposed to air outside the body, certainly oxidize more quickly when in contact with potash (Chevreul, 1825): olein, again, is not acted on by ozone alone, but if potash be added, oxidation sets in at once. We know, also, that albumen, dissolved in water, changes but slowly, while the addition of alkali induces immediate oxidation, and in the ordinary test for diabetic sugar, potash deprives of oxygen even a metallic oxide.

Physiological chemists did not fail to trace a similar action within the body. Lehmann and Mialhe taught that alkalies were powerful promoters of systemic oxidation, and augmented the excretion of urea and carbonic acid. Liebig fully adopted the same view, teaching that they promoted the combustion of "respiratory foods," and pointing out that if organic acids (gallic, citric, etc.) were taken alone, they passed off almost wholly unchanged, but if in combination with alkalies, e.g., as citrate of potash, the acid was "burnt off" in the system, and the alkali passed as a carbonate. The experiments of Frerichs illustrated the same point; he gave urate of potash to rabbits, and yet found no uric acid in the urine, for it became changed into oxalic acid and urea, the excretion of the latter being much increased.

Bence Jones concluded that alkalies, though they could not themselves give up oxygen, decidedly assisted oxidation of organic substances within the body by promoting the formation of acids ("Lectures," and Lancet, i., 1867, p. 202), and Parkes found, in a series of analyses, that the organic material and sulphuric acid excreted in the urine were markedly increased under the use of liquor potassae, which acted, he considered, by increasing the oxidation of sulphur and protein tissues; for this effect it had to be given at least eight hours after food (Medico-Chirurgical Review, 1853). Similar results did not follow the use of acetate or nitrate of potash in Parkes's experiments, but Dr. Golding Bird reported a considerable increase of urea and other urinary solids in the case of a dog submitted to the action of 3 dr. of the acetate ("On Urinary Deposits"). Dr. Reginald Thompson proved by several series of observations, that the amount of phosphoric acid in urine was increased by the administration of carbonate of potash (Medico-Chirurgical Review, ii., 1864).

Besides the cases reported by Dr. Parkes, we have clinical evidence from Dr. Austin Flint of much increase in the urinary solids of a number of patients taking nitrate of potash, and Dr. Basham, observing specially cases of lithic acid diathesis, not only found the urea increased under the use of potash, but oxalic acid appeared as uric acid lessened, and oxalic acid and urea are recognized products of the oxidation of uric acid.

We might almost conclude from the preceding statements that the question as to alkalies increasing oxidation was answered in the affirmative, and yet practical experience shows that some qualifying statement is required, for do we not see marked asthenia, pallor, and anaemia produced in many persons by full doses of alkali, and in all persons by their continued use? (so that Trousseau speaks of their doing more harm than the abuse of iodine or mercury); and moreover, is not temperature reduced by salts of potash, so that they are used as anti-pyretics? whereas, if they increased oxidation, the results should be opposite to these. (Dr. Ridge argues that although some amount of alkali promotes oxidation, the "secondary effect" is to retard it - Medical Times, ii., 1871.) To advance knowledge in this direction, Rabuteau has recently recorded the results obtained on himself, on Constant (of Smyrna), and on a third person (a woman). Each took 5 to 6 grammes of bicarbonate of soda or potash for five to ten days. The full dose of bicarbonate of potash produced a slight diuretic effect, but 5 grammes none at all; urea was markedly and progressively diminished, and depression and anaemia were induced: analogous results were obtained by Ritter, of Nancy; 5 grammes of chlorate equally diminished urea (Fouilhoux, These, Paris, 1874), and 10-gramme doses of nitrate acted in a similar manner (Jovitzu).

The explanation of such contradictory results turns largely upon the question of dosage, as with many other medicines. Large quantities, like those last referred to, will pass out unchanged and quickly, and in their passage so far deteriorate the blood-condition and impair the function of the alimentary tract as to induce asthenia and diminish nutrition; hence, evidently Dr. Parkes's supposition that increasing the dose of potash will proportionately increase oxidation cannot be sustained. Small doses, on the other hand, not only help to saponify fatty food, but aid its oxidation, and that of carbonaceous material generally, improve the digestion, and raise the temperature.

Rabuteau himself confirms these statements, and explains these effects of small doses by their change into chloride in the stomach, and their acting as chlorides rather than as alkalies; under the influence of 5-gramme doses of chloride of potassium he found the excretion of urea increased by 20 per cent.

That potash salts are essential for the development of the animal tissues is shown by the fact that food which in itself is not sufficiently nutritious, such as over-stewed meat, recovers its properties on the addition of these salts and of a little sodium chloride (Binz); the absence of potash salts seems to be at least one cause of scurvy (Garrod). If, on the other hand, we give meat broth which is very rich in potash salts, without adding any other nutrient, tissue-change becomes so accelerated that animals thus fed die earlier than others kept without food.

Experiments with plants show also how necessary potassium is for cell-nutrition; if it be excluded from their soil and water no growth takes place, for without its presence in the chlorophyll granules no starch is produced.

Souligoux, in a recent treatise, emphasizes the necessity of a due amount of alkali for carrying on all the vital processes, and brings evidence to show that a large part of its good effect lies in its favoring proper electrical reactions and currents within the organism ("Etude sur les Alcalins," 1878, Paris).