John H. Galla

Circulating immune complexes and immunoglobulin A rheumatoid factor in patients with mesangial immunoglobulin A nephropathies.

Circulating immune complexes (CIC) containing IgA and C3 were elevated in 48% of IgA nephropathy patients; IgA1 was the predominant subclass. IgA1-IgG CIC were detected in 44%, IgA2-IgG CIC in 7%, and IgM-IgA1 CIC in 16% of the patients. No IgM-IgA2 CIC were detectable. Sucrose gradient ultracentrifugation indicated that IgG-IgA1 CIC were predominantly of intermediate (13-19S) size whereas IgA1-C3 CIC sedimented from 11S to 19S. At acid pH, isolated CIC revealed the presence of substantial amounts of 7S IgA. One third of the patients had elevated serum IgA rheumatoid factor (RF) of both polymeric and monomeric forms despite normal levels of IgM-RF; 87% of patients with elevated IgA-RF had IgA1-IgG CIC. These results indicate that the IgA1 component of CIC in patients with IgA nephropathy is not necessarily of mucosal origin and suggest that a portion of these CIC consists of IgA RF immunologically complexed with autologous IgG.

IgA-associated renal diseases: Antibodies to environmental antigens in sera and deposition of immunoglobulins and antigens in glomeruli

Levels of IgA1, IgA2, IgM, and IgG antibodies specific for 10 ubiquitous food and bacterial antigens were examined by radioimmunoassay in the sera of 29 patients with IgA-associated renal diseases and 22 normal individuals. No significant differences were observed between patient and normal groups in the levels of IgA1 antibodies, and IgA2 antibodies were detected in only a few individuals in either group. Minor differences in IgM or IgG antibodies were seen against some antigens. Significant positive correlations between IgA1 and IgG and between IgA1 and IgM antibodies to casein were found in the patient group. Analysis of the molecular form of serum IgA1 antibodies revealed that although the pattern of polymeric and monomeric forms varied between individuals and between antibody specificities, there was no preponderance of one form in either patient or normal groups. Examination of kidney biopsies from 50 patients with IgA-associated renal diseases revealed that IgA1 represented the predominant subclass deposited in the glomerular mesangium; glomeruli from three patients contained both IgA1 and IgA2. Seventy-eight percent of the patients also had deposits of IgM, although IgA and IgM deposits did not always coincide. When IgG was present in glomeruli (45% of patients), the IgG1 subclass predominated. J chain was detectable in glomeruli of only four patients. C3 was detected in glomeruli of 95% of the patients, although the distribution of C3 did not always coincide with that of IgA. Indirect immunofluorescence staining with rabbit antisera to various environmental antigens showed that milk protein antigens could be deposited in association with IgA in the glomerular mesangium.

Renal filtration and catabolism of complement protein D

Complement protein D, a serine protease participating in the formation of the C3 convertase of the alternative complement pathway, has the lowest molecular weight (23,750) and serum concentration of all complement proteins. In normal serum, D is the rate-limiting protease of the alternative pathway of complement activation. We report that the serum concentrations of D in 20 patients with chronic renal failure (mean +/- S.D., 0.42 +/- 0.28 mg per deciliter) and in 16 patients on long-term dialysis (1.53 +/- 0.39 mg per deciliter) were significantly higher (P less than 0.001) than in 22 healthy adults (0.18 +/- 0.04 mg per deciliter). In chronic renal failure the serum concentration of D correlated with that of creatinine (r = 0.75, P less than 0.001). The serum concentrations of D found in patients with renal failure reached and in some cases exceeded those at which the protease is no longer rate-limiting. Thus, enhanced activity of the alternative pathway of complement should be expected in patients with advanced renal failure. Urinary D was undetectable (less than 0.2 micrograms per deciliter) in 17 normal adults and either undetectable or below the concentration expected from the degree of proteinuria in 10 patients with nephrotic syndrome. However, in a patient with Fanconis syndrome the urinary concentration of D (1.3 mg per deciliter) was an order of magnitude higher than the serum concentration, representing 0.5 per cent of the total protein. The urinary D in this patient had normal hemolytic activity, antigenicity, and size. These results indicate that D is filtered through the glomerular membrane and is probably catabolized in the proximal renal tubules.

Effect of Chloride on Renin and Blood Pressure Responses to Sodium Chloride

Both the inhibition of renin release by sodium chloride and salt-sensitive hypertension have been attributed to sodium. We evaluated the contribution of chloride to these responses to sodium chloride. In the Sprague-Dawley rat, acute and chronic administration of sodium salts other than sodium chloride failed to suppress plasma renin activity, whereas renin was inhibited by both sodium chloride and by selective chloride (without sodium) loading. Plasma renin activity was stimulated by selective chloride depletion. Similarly, in humans, plasma renin activity was suppressed by sodium chloride but not by sodium bicarbonate infusion. In a preliminary study in the Dahl salt-sensitive rat, in contrast to sodium chloride loading, sodium bicarbonate loading failed to produce hypertension. Thus, both the renin and possibly the blood pressure responses to sodium chloride are dependent on chloride.

Differential nephrotoxicity of low molecular weight proteins including Bence Jones proteins in the perfused rat nephron in vivo.

To investigate the pathogenetic mechanisms of tubule nephrotoxicity of low molecular weight proteins (LMWP), proximal tubules (PT) of rats were perfused in vivo with artificial tubule fluid (ATF) containing one of five LMWPs: three human Bence Jones proteins (BJP), beta-lactoglobulin (BLG), and rabbit myoglobin (MYG). Volume (JV), chloride (JCl) and glucose (JG) fluxes in these perfused PTs were compared with those determined using ATF alone. In separate experiments, perfused nephrons were examined with electron and immunoelectron microscopy. After exposure to BJP1 or BLG, JV, JCl, and JG were less (P less than 0.05) than corresponding control fluxes. Cell damage of these perfused PTs, along with cellular debris in the distal tubules, was prominent. The PT lysosomes often appeared atypical and contained crystals. In contrast, perfusion with BJP2, BJP3, or MYG did not alter JV, JCl, or JG. These findings were corroborated by the normal ultrastructure of these PTs despite immunohistochemical evidence of endocytosis of the BJPs. Isoelectric point, molecular form, and isotype were not factors associated with PT damage. In addition, proteins with pI less than 7.4 precipitated in the distal nephron, forming acellular casts. Thus, certain nephrotoxic LMWPs damaged the PT, while others precipitated in the distal tubule, obstructing the nephron. These two pathogenetic mechanisms may independently be responsible for tubulointerstitial nephropathy of LMWPs in humans.

Assessing acid-base disorders

Effective management of acid-base disorders depends on accurate diagnosis. Three distinct approaches are currently used in assessing acid-base disorders: the physiological approach, the base-excess approach, and the physicochemical approach. There are considerable differences among the three approaches. In this review, we first describe the conceptual framework of each approach, and comment on its attributes and drawbacks. We then highlight the application of each approach to patient care. We conclude with a brief synthesis and our recommendations for choosing an approach.

It Is Chloride Depletion Alkalosis, Not Contraction Alkalosis

Maintenance of metabolic alkalosis generated by chloride depletion is often attributed to volume contraction. In balance and clearance studies in rats and humans, we showed that chloride repletion in the face of persisting alkali loading, volume contraction, and potassium and sodium depletion completely corrects alkalosis by a renal mechanism. Nephron segment studies strongly suggest the corrective response is orchestrated in the collecting duct, which has several transporters integral to acid-base regulation, the most important of which is pendrin, a luminal Cl/HCO(3)(-) exchanger. Chloride depletion alkalosis should replace the notion of contraction alkalosis.

HCO 3 − reabsorption in renal collecting duct of NHE-3-deficient mouse: a compensatory response

Mice with a targeted disruption of Na+/H+exchanger NHE-3 gene show significant reduction in[Formula: see text] reabsorption in proximal tubule, consistent with the absence of NHE-3. Serum[Formula: see text], however, is only mildly decreased (P. Schulties, L. L. Clarke, P. Meneton, M. L. Miller, M. Soleimani, L. R. Gawenis, T. M. Riddle, J. J. Duffy, T. Doetschman, T. Wang, G. Giebisch, P. S. Aronson, J. N. Lorenz, and G. E. Shull. Nature Genet. 19: 282-285, 1998), indicating possible adaptive upregulation of[Formula: see text]-absorbing transporters in collecting duct of NHE-3-deficient (NHE-3 -/-) mice. Cortical collecting duct (CCD) and outer medullary collecting duct (OMCD) were perfused, and total CO2 (net[Formula: see text] flux, J tCO2) was measured in the presence of 10 μM Schering 28080 (SCH, inhibitor of gastric H+-K+-ATPase) or 50 μM diethylestilbestrol (DES, inhibitor of H+-ATPase) in both mutant and wild-type (WT) animals. In CCD, J tCO2increased in NHE-3 mutant mice (3.42 ± 0.28 in WT to 5.71 ± 0.39 pmol ⋅ min-1 ⋅ mm tubule-1 in mutants, P < 0.001). The SCH-sensitive net[Formula: see text] flux remained unchanged, whereas the DES-sensitive [Formula: see text] flux increased in the CCD of NHE-3 mutant animals. In OMCD, J tCO2increased in NHE-3 mutant mice (8.8 ± 0.7 in WT to 14.2 ± 0.6 pmol ⋅ min-1 ⋅ mm tubule-1 in mutants, P < 0.001). Both the SCH-sensitive and the DES-sensitive [Formula: see text] fluxes increased in the OMCD of NHE-3 mutant animals. Northern hybridizations demonstrated enhanced expression of the basolateral Cl-/[Formula: see text]exchanger (AE-1) mRNA in the cortex. The gastric H+-K+-ATPase mRNA showed upregulation in the medulla but not the cortex of NHE-3 mutant mice. Our results indicate that[Formula: see text] reabsorption is enhanced in CCD and OMCD of NHE-3-deficient mice. In CCD, H+-ATPase, and in the OMCD, both H+-ATPase and gastric H+-K+-ATPase contribute to the enhanced compensatory[Formula: see text] reabsorption in NHE-3-deficient animals.

Effects of chloride and extracellular fluid volume on bicarbonate reabsorption along the nephron in metabolic alkalosis in the rat. Reassessment of the classical hypothesis of the pathogenesis of metabolic alkalosis.

Volume expansion has been considered essential for the correction of chloride-depletion metabolic alkalosis (CDA). To examine the predictions of this hypothesis, rats dialyzed against 0.15 M NaHCO3 to produce CDA and controls, CON, dialyzed against Ringer-HCO3 were infused with either 6% albumin (VE) or 80 mM non-sodium chloride salts (CC) added to 5% dextrose (DX) and studied by micropuncture. CDA was maintained in rats infused with DX. VE expanded plasma volume (25%), maintained glomerular filtration rate (GFR), but did not correct CDA despite increased fractional delivery of total CO2 (tCO2) out of the proximal tubule (36 +/- 2%) as compared with VE/CON (24 +/- 4%; P less than 0.05). In contrast, CC corrected CDA despite volume contraction (-16%) and lower GFR than CC/CON; proximal tCO2 delivery in CC/CDA (29 +/- 4%) did not differ from VE/CDA. CC was associated with an increment in tCO2 excretion. The data strongly suggest that maintenance and correction of CDA are primarily dependent upon total body chloride and its influences on intrarenal mechanisms and not on the demands of sodium or fluid homeostasis.

K+ depletion increases HCO3- reabsorption in OMCD by activation of colonic H(+)-K(+)-ATPase.

To probe the role of the isoforms of H(+)-K(+)-ATPase (HKA) in potassium depletion (KD), rats were placed on a KD diet for 2 wk. Colonic HKA (cHKA) mRNA levels increased approximately 30-fold in outer medulla, and net HCO3-flux (JtCO2) in outer medullary collecting duct (OMCD) increased (13.1 pmol.min-1.mm tubule length-1 in control to 17.7 pmol.min-1.mm tubule length-1 in KD; P < 0.01). In normal rats, 1 mM ouabain in perfusate had no effect on JtCO2, whereas 10 microM Sch-28080 decreased JtCO2 to 5.1 pmol.min-1.mm tubule length-1 (P < 0.001). In KD rats, ouabain 1 mM decreased JtCO2 to 6.3 pmol.min-1.mm tubule length-1 (P < 0.001). Although 10 microM Sch-28080 also decreased JtCO2 to 4.6 pmol.min-1.mm tubule length-1 (P < 0.001), the inhibitory effects of Sch-28080 and ouabain were not additive. Removal of K+ from perfusate blocked Sch-28080-sensitive JtCO2 in both normal and KD tubules. The data suggest that, in KD, cHKA is induced and mediates increased HCO3-reabsorption in OMCD, cHKA in vivo is sensitive to both Sch-28080 and ouabain, and cHKA activity is dominant.