Neil A. Kurtzman

Cisplatin Nephrotoxicity: A Review

Background:Cisplatin is a major antineoplastic drug for the treatment of solid tumors, but it has dose-dependent renal toxicity. Methods:We reviewed clinical and experimental literature on cisplatin nephrotoxicity to identify new information on the mechanism of injury and potential approaches to prevention and/or treatment. Results:Unbound cisplatin is freely filtered at the glomerulus and taken up into renal tubular cells mainly by a transport-mediated process. The drug is at least partially metabolized into toxic species. Cisplatin has multiple intracellular effects, including regulating genes, causing direct cytotoxicity with reactive oxygen species, activating mitogen-activated protein kinases, inducing apoptosis, and stimulating inflammation and fibrogenesis. These events cause tubular damage and tubular dysfunction with sodium, potassium, and magnesium wasting. Most patients have a reversible decrease in glomerular filtration, but some have an irreversible decrease in glomerular filtration. Volume expansion and saline diuresis remain the most effective preventive strategies. Conclusions:Understanding the mechanisms of injury has led to multiple approaches to prevention. Furthermore, the experimental approaches in these studies with cisplatin are potentially applicable to other drugs causing renal dysfunction.

Regulation of collecting tubule adenosine triphosphatases by aldosterone and potassium.

To examine the precise role of potassium and aldosterone on acid-base composition and on collecting tubule ATPases, glucocorticoid-replete adrenalectomized rats were replaced with zero, physiological, or pharmacological doses of aldosterone and were fed varying potassium diets to produce hypokalemia, normokalemia, or hyperkalemia. Radiochemical measurement of ATPase activities showed that collecting tubule H/K-ATPase changed inversely with potassium and not with aldosterone whereas H-ATPase changed directly with aldosterone but not with potassium. When both enzymes changed in the same direction, alterations in acid-base composition were profound; however, when these two acidifying enzymes changed in opposite directions or when only one enzyme changed, the effect on acid-base balance was modest. Serum bicarbonate was approximately 45 meq/liter when aldosterone was high and potassium was low; it was only 29 meq/liter when aldosterone was high but potassium was normal or when aldosterone was normal and potassium was low. Our observations may help explain the metabolic alkalosis of primary aldosteronism in which aldosterone excess and hypokalemia are combined and the metabolic acidosis of aldosterone deficiency in which hypoaldosteronism and hyperkalemia are paired. The present study also demonstrated that aldosterone plays the major role in controlling Na/K-ATPase activity in cortical collecting tubule. Hypokalemia stimulates Na/K-ATPase activity in the medullary collecting tubule; this stimulatory effect of hypokalemia supports the hypothesis that the enzyme is present on the apical membrane at this site.

A Patient With Hyperkalemia and Metabolic Acidosis

Uptake of potassium by extrarenal tissues, primarily muscle and liver, represents a major defense mechanism in the maintenance of normokalemia following an acute elevation in the serum potassium concentration. Insulin, epinephrine, and aldosterone all play major roles in maintaining the normal distribution of potassium between the intracellular and extracellular environment. In addition to hormonal regulation, changes in blood pH and tonicity also exert a strong influence on extrarenal potassium metabolism. Last, the serum potassium concentration per se directly influences its own cellular uptake and this transport mechanism appears to be inhibited by uremia.

Acid-base disorders in medicine

The practice of internal medicine involves daily exposure to abnormalities of acid-base balance. A wide variety of disease states either predispose patients to develop these conditions or lead to the use of medications that alter renal, gastrointestinal, or pulmonary function and secondarily alter acid-base balance. In addition, primary acid-base disease follows specific forms of renal tubular dysfunction (renal tubular acidosis). We review the acid-base physiologic functions of the kidney and gastrointestinal tract and the current understanding of acid-base pathophysiologic conditions. This includes a review of whole animal and renal tubular physiologic characteristics and a discussion of the current knowledge of the molecular biology of acid-base transport. We stress an approach to diagnosis that relies on knowledge of acid-base physiologic function, and we include discussion of the appropriate treatment of each disorder considered. Finally, we include a discussion of the effects of acidosis and alkalosis on human physiologic functions.

Diseases of Renal Adenosine Triphosphatase

Most renal transport is a primary or secondary result of the action of one of three membrane bound ion translocating ATPase pumps. The proximal tubule mechanisms for the reabsorption of salt, volume, organic compounds, phosphate, and most bicarbonate reabsorption depend upon the generation and maintenance of a low intracellular sodium concentration by the basolateral membrane Na-K-ATPase pump. The reabsorption of fluid and salt in the loop of Henle is similarly dependent on the energy provided by Na-K-ATPase activity. Some proximal tubule bicarbonate reabsorption and all distal nephron proton excretion is a product of one of two proton translocating ATPase pumps, either an electrogenie H-ATPase or an electroneutral H-K-ATPase. In this article, the authors review the biochemistry and physiology of pump activity and consider the pathophysiology of proximal and distal renal tubular acidosis, the Fanconi syndrome, and Bartters syndrome as disorders of ATPase pump function.

Nephrotic syndrome and renal failure associated with a novel glycolipid storage disorder.

A 57-year-old Caucasian male presented with severe nephrotic syndrome and diffuse organomegaly; he subsequently developed renal failure and died. Intracellular, crystalloid material was identified by light and electron microscopy in bone marrow, liver, spleen, mesenteric lymph nodes, and kidneys. Tissue extraction analysis identified the material as glucocerebroside and its immediate precursor, ceramide lactoside. Although Gauchers disease cannot be completely excluded, glycolipid profiles do not conform to those of known storage disorders. Additionally, electron-microscopic studies indicate that the structural features of the glycolipid deposits are different from those of previously described storage diseases. These findings suggest a unique crystalloid deposition as the probable cause of a multisystem process, which was associated with renal insufficiency and death.

Anemia and Cardiovascular Complications: Iron and EPO Impact

Management of end-stage renal disease (ESRD) has been revolutionized by the advent of erythropoietin replacement. We briefly review its characteristics and clinical use. Also emphasized is the importance of iron deficiency in limiting the clinical response to erythropoietin therapy. Iron-replacement therapy in ESRD patients is briefly discussed.

Metabolic Alkalosis: Biochemical Mechanisms, Pathophysiology, and Treatment

Metabolic alkalosis is a primary pathophysiologic event characterized by the gain of bicarbonate or the loss of nonvolatile acid from extracellular fluid such that arterial pH increases (normal pH = 7.40). More simply put, it is a primary increase in plasma bicarbonate concentration (normal plasma HCO3 = 24mEq/L). Like all acid-base disturbances, metabolic alkalosis commonly complicates the course of patients with preexisting disorders. An understanding of its pathophysiology makes the diagnosis and management of metabolic alkalosis a relatively simple process. Several series (1,2) have reported that metabolic alkalosis is the second most common acid-base disorder in hospitalized adults (Table 1). Most of these are patients with other underlying diseases predisposing them to one of the many complex acid-base disorders.

Effect of vanadate in acute metabolic acidosis

Summary: The effect of vanadate on urinary excretion of acid and electrolyte in dogs with hydrochloric acid (HCI)‐induced acute metabolic acidosis was studied. Vanadate caused no changes in systemic and renal haemodynamics, blood parameters and net acid excretion (NAE) in the control group. In the acute metabolic acidosis group, metabolic acidosis per se also had no effect on haemodymic parameters. Fractional excretion of bicarbonate was decreased, while NAE was markedly increased. Following vanadate treatment, acute acid‐loaded animals showed an increase in mean arterial pressure (MAP), but a decreased glomerular filtration rate and effective renal plasma flow. These animals had reduced NAE compared to that seen with HCI alone. Thus, vanadate impaired the renal adaptive responses to acute metabolic acidosis. the decreased NAE induced by vanadate might be caused by its known inhibitory effect on hydrogen‐potassium‐adenosine triphosphatase (H‐K‐ATPase) and sodium‐potassium‐adenosine triphosphatase (Na‐K‐ATPase), and by renal vasoconstriction.

Effects of pH on calcium transport in turtle bladder

This study was designed to examine the effect of apical and basolateral (ie, mucosal and serosal) pH on calcium (Ca) transport in turtle bladder, a nonmammalian analog of the distal nephron. Unidirectional Ca45 fluxes were measured when serosal pH was 6.4, 7.4, or 8.4 (mucosal pH, 7.4) in the presence and absence of ouabain. When serosal pH was 8.4, M-->S Ca45 flux increased significantly, and when it was 6.4, M-->S Ca45 flux decreased markedly. Changes in serosal pH did not affect the S-->M Ca45 flux. When 5 x 10(-4) mol/L ouabain was added to inhibit sodium transport, M-->S Ca45 flux, at pH 7.4, was 221.6 +/- 27.4 pmol/mg/h (n = 10), and low pH again inhibited this flux (approximately 50%). Lowering mucosal pH (with serosal pH 7.4) also decreased M-->S Ca45 flux. In stripped bladders, Ca45 uptake increased linearly as medium pH was increased from 4.4 to 8.4. Total tissue Ca concentration did not change when serosal pH was varied, except at the extreme of pH 4.4, where tissue Ca decreased. By contrast, when apical pH was 6.4, tissue Ca rose substantially (approximately 1.5-fold). these results demonstrate that extracellular pH directly affects Ca homeostasis in the turtle bladder. Lowering the pH of either the serosal or mucosal medium directly inhibits apical Ca permeability. This change in Ca permeability is seen in the presence of ouabain. By contrast, alkalization of the serosal medium enhances apical permeability, but this effect is, in some manner, related to sodium transport.(ABSTRACT TRUNCATED AT 250 WORDS)