Resumo

PENA RODRIGUEZ, José Carlos. The wisdom of the kidney II. Urine concentration and the countercurrent multiplier mechanism of the loop of Henle. Acta méd. Grupo Ángeles [online]. 2021, vol.19, n.2, pp.304-312.  Epub 23-Nov-2021. ISSN 1870-7203.  https://doi.org/10.35366/100465.

In the middle (1950) of the last century, an interesting controversy on the mechanisms of the urine concentration, evolved. In which, Dr. Homer W. Smith the great leader of Renal Physiology at that time, actively participated. Until that moment, the nephron was drawn in a rectilinear fashion, without the presence of the Henle´s Loop. Dr. Smith considered the loop an incident of organogenesis with no functional significance. In that year during the XVIII International Congress in Copenhagen, he was faced with the data presented to him by his former fellow, M.D. Heinrich Wirz from the University of Basel, Switzerland. The observations of H. Wirz, consisted of measurements of the osmotic pressure at various levels of the rat kidney and showed as that the fluids in the cortex were isosmotic to plasma, the medulla depicted a continuous increase in osmotic pressure from the cortico-medullary junction up to the papilla. In this environment the urine travelling along the nephron from cortex to papilla particularly the collecting that became progressively concentrated. To explain this surprising results, Bartholomaüs Hargitay y Werner Kuhne, of the University of Basel, invoked a principle known as the countercurrent multiplier; wherein the opposing streams in the descending and ascending limbs of the loop of Henle played an important role. In the course of this review is analyzed the results published along that decade with the physiological concepts accepted in that period. Among the papers revised, excel the articles published by H. Wirz an collaborators, Carl Gottschalk and Margaret Mylle, plus the punctual and exhaustive analysis of the most important publications of that period, all included in this review. At the end, Dr. Smith accepted the fundamentals of the concentrating mechanism and the countercurrent hypothesis as concevied by all the authors mentioned. At the end of this review is described the osmolar concentration during severe dehydration, in the inner medulla and the papilla. For this condition, until today, there is not a plausible explanation.

Palavras-chave : Countercurrent multiplier mechanism; loop of Henle; ascending branch of the loop of Henle; collecting tube; concentration; dilution.

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