Bobby J. Stinebaugh

Distal renal tubular acidosis syndromes: a pathophysiological approach.

Ammonium is the most important component of renal acid excretion. A reduced rate of ammonium excretion is the common feature of the group of diseases called distal renal tubular acidosis. We have presented an alternative approach to patients with distal acidification defects based upon the pathophysiology of these disorders. Accordingly, the purpose of this review is to describe a revised classification based on our current understanding of collecting duct hydrogen ion secretion and ammonium addition to the lumen of the distal nephron. We have subdivided these defects into four groups: disorders of the collecting duct proton pump (pump defects); failure to generate and/or maintain an appropriate electrical gradient to favor hydrogen ion secretion (voltage defects); back-leak of hydrogen ions across an abnormally permeable collecting duct membrane (gradient defects), and diminished availability of NH3 in this nephron segment (NH3 defects). These four subtypes can be identified by measuring the urine pH and PCO2 under appropriate circumstances and evaluating the renal excretion of ammonium and potassium.

Evaluation of the effect of pentobarbitone anaesthesia on the plasma potassium concentration in the rabbit and the dog

The purpose of these studies was to determine the reasons for the hypokalaemia observed in rabbits studied in our laboratory. The rabbits consumed standard rabbit chow which is rich in potassium and remained in potassium balance. Hypokalaemia was only observed following anaesthesia. A number of additional investigations were undertaken to clarify the mechanisms involved. The hypokalaemia could not be attributed to technical factors, alkalaemia, hyperinsulinaemia or hyperaldosteronism, but seemed to be a function of anaesthesia. This effect of pentobarbitone anaesthesia was not unique to the rabbit, as similar changes also occurred in the anaesthetized dog.The findings reported in this paper have significant implications with respect to the interpretation of plasma potassium concentrations in anaesthetized subjects or animals.RésuméLe but de cette eétude était de déterminer la cause de l’hypokaliémie observée à la suite de l’anesthésie des lapins de laboratoire. Ces lapins consommaient une moulée standard à lapins riche en potassium et capable de maintenir en balance cet électrolyte. Plusieurs investigations supplémentaires furent entreprises pour élucider les mécanismes responsables. La baisse de la kaliémie ne put être attribuée à des facteurs techniques, à l’alcalémie, l’hyperinsulinémie ou 1’hyperaldostéronisme mais semblait bien être une conséquence de l’anesthésie au pentobarbitone. Cet effet ne survenait pas uniquement sur les lapins mais aussi sur les chiens anesthesies.Les données rapportées dans ce travail peuvent modifier significativement 1’interprétation des résultats d’analyse de la kaliémie plasmatique chez les patients et les animaux anesthésiés.

Disequilibrium pH and bicarbonate reabsorption: relevance to the pathogenesis of distal renal tubular acidosis.

An augmented renal capacity to reabsorb bicarbonate (RHCO3) has been noted in patients with distal renal tubular acidosis (dRTA), and construed as evidence that the basic defect in dRTA is abnormal distal tubular permeability. According to this interpretation, the absence of a disequilibrium pH due to a back-leak of H2C03 permits increased distal H+ secretion and results in an increased RHCO3. To test this assumption, we have evaluated the effect of acute elimination of the disequilibrium pH by carbonic anhydrase infusion. The results establish that this maneuver doses not cause a rise in RHCO3. Thus, the elevated value of RHC3 described in dRTA cannot be the consequence of increased back-diffusion of H2CO3 and is more likely due to coexisting extracellular volume depletion and/or postassium deficiency.

Renal Excretion of Calcium and Magnesium during Acetazolamide or Parathyroid Hormone Administration in Dogs with Distal Blockade

Renal absorption of calcium and magnesium occurs in the proximal tubule, and at unknown site(s) beyond this segment. In the presence of blockade of Henle’s loop by ethacrynic acid, the excretion of ca