Charles Toussaint

Effects of hypercalcemia on water and sodium excretion by the isolated dog kidney

SummaryThe effects of acute hypercalcemia on hemodynamics and on water and sodium excretion were studied on the blood-perfused isolated dog kidney. This model advantageously eliminates various factors which modify medullary osmolality and intrarenal hemodynamics, as well as collecting duct permeability. Calcium ion directly inhibits sodium reabsorption in the proximal tubule and in the ascending limb of Henles loop, leading to increased sodium excretion rate and to decreased free water generation. The vasoconstrictive action of calcium, leading to decreased glomerular filtration rate, may mitigate the strong natriuretic effect of this ion.

Renal tubular transport of sodium during sodium chloride and sodium bicarbonate loadings in the normal dog

La réabsorption tubulaire des ions sodium, chlore et bicarbonate a été étudiée au cours de perfusions de NaCl et de NaHCO3 chez le chien normal. 61 expériences, comportant un ensemble de 295 récoltes urinaires, ont été pratiquées sur 21 animaux. A filtration constante, la réabsorption du sodium exprimée enmM/l de filtrat glomérulaire demeure constante lorsque la natrémie est accrue par linfusion de NaHCO3. Elle est, au contraire, une fonction linéaire de la natrémie lorsque celle-ci est élevée par des perfusions de NaCl. Dans le premier cas, la réabsorption du sodium seffectue par un double mécanisme: lun, lié à la réabsorption du bicarbonate, est fixé par un Tm constant, lautre, lié à la réabsorption du chlore, dépend de la chlorémie. Lorsque la natrémie est accrue par linfusion de NaCl, le second mécanisme lemporte nettement sur le premier. Il apparaît alors une relation évidente entre la natrémie (ou la chlorémie) et la quantité de sodium (ou de chlore) réabsorbée par les tubes rénaux.

Role of the peritubular oncotic pressure on sodium excretion by the avian kidney

SummaryThe introduction of oncotically active substances, such as dextran and human serum albumin, into the renal portal vein of the cock is followed by a reduction of sodium excretion rate by the injected kidney, the contralateral organ acting as control. This observation demonstrates that the transtubular oncotic pressure gradient plays some role in sodium transport by the renal tubules. The implications of this finding are confronted with the clearance and micropuncture data obtained in the course of saline diuresis in other species.

Effects of Large Doses of Furosemide in End-Stage Chronic Renal Failure

Administered orally at 500 mg/day to patients in end-stage chronic renal failure treated by hemodialysis, furosemide significantly decreases the weight gain between dialyses and increases sodium excretion rate. This therapy remains without effect on blood pressure, creatinine clearance and urinary excretion of potassium and nitrogen. Devoid of any side-effects, at least during short periods, the treatment may contribute to achieve better control of sodium and water balance.

Bicarbonate excretion after prolonged exposure to carbon dioxide in the normal dog.

Lexcrétion du bicarbonate a été étudiée chez des chiens ayant préalablement séjourné pendant des périodes de 4 à 6 jours dans une atmosphère contenant de 7 à 10% de CO2. Ce procédé a pour effet daccroître fortement la réabsorption tubulaire du bicarbonate par un mécanisme distinct de laction de laccroissement de la pression partielle du CO2 et analogue à celui qui augmente la réabsorption du bicarbonate au cours de lhypochlorémie aiguë réalisée par des procédés de vividialyse.

Effects of plasmapheresis on renal hemodynamics and sodium excretion in dogs

SummaryAcute plasmapheresis in dogs reduces plasma protein concentration, without significantly altering plasma volume, glomerular filtration rate and plasma sodium concentration.The effects of acute hypoproteinemia on renal circulation is variable. In some cases, the renal plasma flow is not modified, while in others it is markedly decreased, leading to a rise in filtration fraction. The hemodynamic changes are observed in experiments inducing marked protein depletion.Acute hypoproteinemia increases sodium excretion exclusively in experiments where plasmapheresis has not reduced kidney irrigation.The lack of plasma volume expansion in the natriuretic animals cancels the necessity of postulating the secretion of some unknown natriuretic hormone to explain the decreased tubular reabsorption of sodium. The explanation of “saline diuresis” should be sought within the kidney itself, and the fall in peritubular oncotic pressure, occurring after plasmapheresis or during massive saline loading, offers an alternative explanation, which appears simpler and more rational.

Effect of potassium salts administration on the renal excretion of bicarbonate during acute respiratory acidosis and hypochloremic alkalosis in the dog.

Leffet dinfusions de KCl et de KHCO3 a été étudié chez des chiens soumis à deux situations aiguës caractérisées par un accroissement de la réabsorption du bicarbonate: lacidose respiratoire et lalcalose hypochlorémique. Les deux sels diminuent fortement la réabsorption du bicarbonate au cours de lacidose respiratoire mais le KCl est beaucoup plus efficace dans lalcalose hypochlorémique où le KHCO3 paraît dépourvu deffet.

Erythropoiesis in renal insufficiency and in anephric man.

While the role of the kidney in erythropoiesis has been experimentally demonstrated,1.2 we have only indirect arguments concerning the eventual production of erythropoietin by this organ in man. The fact that acute anuria is followed by a sudden and marked depletion of the erythroid as opposed to the moderate normoblastic depression observed in chronic renal disease, has led us to think that uremic intoxication is not the main cause of the erythropoietic depression in renal insufficiency, but that the kidney has a predominent role in erythropoiesis independent of its excretory function.2 Erythropoietin plasma level is not measurable in patients with chronic renal disorders regardless of the severity of anemia, while increased values are generally found in patients with similar anemia but normal renal f~nction.5.~ On the other hand, polycythemia has been reported in some renal diseases (renal tumors, cysts or hydronephrosis) . In certain cases erythropoietin has been detected in plasma and in tumor extracts or cystic fl~id.~JO These facts corroborate the hypothesis that in man, the kidney is concerned with the elaboration of erythropoietin, if not with the exclusive source of the hormone. In this study we have presented determinations of erythropoietin plasma levels in patients with chronic uremia or acute anuria, treated or not by extrarenal epuration, nephrectomy or transplantation, and compared the modifications of normoblast percentage observed in the bone marrow after nephrectomy or acute anuria.

Interactions between furosemide and vasopressin on hemodynamics and on water excretion by the isolated dog kidney

SummaryThe effects of furosemide were studied on isolated dog kidneys in the absence and in the presence of vasopressin. In the latter condition, furosemide did not modify renal blood flow and glomerular filtration rate while both parameters were decreased by the drug in the absence of vasopressin, as they were also reduced by vasopressin alone. This would indicate direct vasoactive effects of furosemide, depending on the previous tone of the vasculature. In the absence of vasopressin, furosemide decreased free water clearance through inhibition of sodium reabsorption in the ascending limb of Henles loop. On the other hand, in the presence of vasopressin, furosemide increased free water clearance, presumably through reduction of water reabsorption in the collecting duct by enhanced distal tubular flux.

Effects of stimulation and inhibition of bicarbonate reabsorption on the renal tubular transport of sodium and chloride in the dog

Lacidose respiratoire aiguë naffecte pas significativement la réabsorption tubulaire du Na et du Cl, alors que celle-ci est déprimée par ladministration dacétazolamide.