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Glycosuria in Phloridzin Poisoning

sugar, diabetes, blood, mellitus, kidneys, albumin and urine


The form of glycosuria which we are about to study, namely, that occurring in phloridzin poisoning, has thrown no greater light upon the problem of diabetes than did the experiments which we have just considered. Yet our acquaintance with it has added in an im portant degree to our knowledge of the process of sugar formation in the animal organism. Phloridzin is a glucoside obtained from the bark of the root of apple and cherry trees. In 1886 v. Mering an nounced that after the administration of this substance to clogs and rabbits there was an excretion of a large percentage of sugar in the urine. A few hours after the exhibition to dogs of about one gram of phloridzin to every kilogram of the animal's weight, the urine is found to contain 10 per cent. or more of grape sugar. The glycosuria persists as long as the administration of phloridzin is continued. The same result can be obtained also in the human subject, in whom the ingestion of phloridzin produces no injurious consequences. The sugar appears in the urine indifferently whether carbohydrates have been previously ingested or whether the individual be fasting or living upon a flesh diet. In experiments upon animals sugar was excreted even when the dogs had been fasting so long that no glyco gen, or at most only traces, could have been present in the liver or muscles. We see here, therefore, a very remarkable difference be tween the previously described forms of glycosuria and that which follows phloridzin poisoning, and recognize at once that the occur rence of the two forms must be very differently explained. More exact investigations have furnished this desired explanation.• Other observers as well as v. Mering found that the blood was poor in grape sugar during the phloridzin glycosuria, a condition of this fluid exactly the opposite of that which exists after piqare and over feeding. There is now scarcely any doubt that phloridzin acts pri marily upon the kidneys, so changing the renal epithelium as to destroy its normal power of keeping back sugar and to cause it to seize greedily upon the sugar held in solution in the blood. Hence comes it that the blood is found to be poor in sugar. This drawing of sugar from the blood is at once met by a discharge from the gly cogen reservoirs, and when the supply of glycogen is exhausted new sugar is formed in order to maintain the percentage of sugar in the blood, which is a matter of so great importance, at its normal height.

Under these conditions albumin is used for the sugar production, either the albumin of the food or, when the individual is fasting, the albumin of the tissues.

The study of phloridzin diabetes has, more than all other previ ous researches, established the certainty that the albuminates may become a source of sugar production. It has not yet been definitely settled whether or not fat also may be drawn upon as an adjuvant in furnishing a supply of sugar to the blood, in case of phloridzin poisoning.

The lesson of phloridzin poisoning is important from another point of view. It has pointed out to us an entirely new way, and one that is full of surprising aspects, by which glycosuria may be produced. We have as yet, however, no ground for the assumption that the clinical affection, diabetes mellitus, ever arises in this way. Still we must remember that, in the history of diabetes mellitus, the view has often been expressed by well-known authorities that this is a primary affection of the kidneys. For example, Dickinson treats of diabetes mellitus in his work on " Diseases of the Kidneys," pub lished in 1875, and in earlier times we meet with this opinion still more frequently (Galen, Theophrastus, Paracelsus). The present Las offered a long-defeiTed reparation to these authors in so far as it has been shown by phloridzin poisoning that there is a form of gly cosuria and even, if one cares to use the term, diabetes mellitus, which is dependent upon disease of the kidneys. This experience warns us not to reject absolutely the possibility that such a patho genesis may be present in true diabetes mellitus. As was said above, we have not the slightest ground for such an opinion; but it is possi ble that there are other poisons, gaining access to the human organ ism in some manner unknown to us, which may produce changes in the kidneys similar to those caused by phloridzin. The doctrine, which has indeed for a long time been questioned, that diabetes melli tus is a morbid entity, can now no longer be upheld on theoretical grounds.