摘要:

Previous studies have shown that the clearance of lithium (Cli) is a quantitative measure of the delivery of tubular fluid to Henle’s loop in rats given food with an ordinary or high sodium content, but not in rats given food with a low sodium content, because under these latter circumstances lithium is also reabsorbed to some extent in the distal nephron. The present study examines the effect of acetazolamide, hydrochlorothiazide, furosemide, and amiloride on the distal reabsorption of lithium in conscious rats with hereditary diabetes insipidus fed standard diets with medium (300 mmol Na/kg) and low (5 mmol Na/kg) sodium contents, respectively. Low sodium diet induced distal Li reabsorption, as apparent from the decrease in CLi and a fall in the urine/plasma lithium concentration ratio (U/P)Li to below 1.0. Amiloride and furosemide abolished the distal Li reabsorption. Acetazolamide also abolished distal Li reabsorption and, in addition, it increased the fluid output from the proximal tubules. Hydrochlorothiazide was unable to abolish distal Li reabsorptio

ISSN:1420-4096    

DOI:10.1159/000173070

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

At present the detailed mechanism for transmembrane interactions is not known and a protein linked to the endoskeleton as well as to the exoskeleton has not been described as yet. The H2 complex, a transmembrane protein, consists of heavy and light chains, the latter is named beta-2-microglobulin. In order to look for an association of beta-2-microglobulin with an exoskeleton protein, we examined the extracellular matrix proteins, collagen type I, type IV, fibronectin, amyloid P, the solubilized glomerular basement membrane and lamiriin in respect to their interaction with the light chain. The heavy chain is known to bind strongly to the endoskeleton protein actin. Only laminin and the glomerular basement membrane bound firmly to the beta-2-microglobulin; 3 M urea was necessary to dissociate the formed complex. Incubation with beta-2-microglobulin antibody prevented binding of beta-2-microglobulin to laminin and the glomerular basement membrane on affinity chromatography columns. Antiserum to the glomerular basement membrane in turn prevented binding of beta-2-microglobulin to the glomerular basement membrane, whereas antibodies against the basement membrane collagen type IV failed to inhibit this binding to the glomerular basement membrane. Beta-2-microglobulin also bound to ñbronectin but this complex was dissociated with 1 M urea. In a rosette assay beta-2-microglobulin antibody and antiserum to the glomerular basement membrane reduced attachment of glomerular cells to beads coupled with laminin and solubilized glomerular cells to beads coupled with laminin and solubilized glomerular basement membrane. Also antibody against fibronectin reduced attachment of glomerular cells to fibronectin-coated beads. In an organ reconstruction assay, glomerular cells showed reduced binding to the glomerular scaffold if antibodies to the solubilized glomerular basement membrane or fibronectin were applied, but not if anti-type-IV collagen antibodies were used. This points to the role of laminin and fibronectin for the attachment to glomerular cells, where the receptor could be identified as beta-2-microglobulin, the light chain of the H2 complex, thus linking the endoskeleton with the exoskeleton. Only differences in the binding affinities between laminin and fibronectin were detected

ISSN:1420-4096    

DOI:10.1159/000173071

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Autoregulatory efficiency of renal blood flow (RBF) and glomerular filtration rate (GFR) was evaluated in 12 anesthetized dogs that had been maintained on low-sodium diet during control conditions and following infusion of an angiotensin-converting enzyme inhibitor (captopril). Converting enzyme inhibition (CEI) decreased systemic blood pressure by 15.5 ± 3.5%, increased RBF by 36.3 ± 6.5%, and increased GFR by 25.9 ± 10.7%. In response to reductions in renal arterial pressure, RBF was efficiently autoregulated and did not change significantly until the 89- to 75-mm Hg range during the control period and the 74- to 54-mm Hg range during CEI. Overall GFR autoregulatory efficiency was generally well maintained during CEI; however, evaluation of the coupled autoregulatory efficiency of RBF and GFR indicated that during angiotensin blockade, there was a greater incidence of a dissociation between RBF and GFR autoregulatory efficiency. Six of the 12 dogs showed reduced GFR autoregulatory efficiency at renal arterial pressures where RBF was still well maintained. Thus, while the data indicate that blockade of the renin-angiotensin system does not abolish the basic capability of the kidney to autoregulate either RBF or GFR efficiently, more subtle influences on the coupling of RBF and GFR autoregulatory efficiency were observed at the lower level of the autoregulatory ran

ISSN:1420-4096    

DOI:10.1159/000173072

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

Clearance and micropuncture experiments were performed on male Cercopithecus monkeys weighing between 2 and 4 kg to evaluate the function of the superficial nephron. The mean glomerular filtration rate was 4.47 ± 0.32 ml/min. The fraction of filtered sodium, potassium, calcium, magnesium, and phosphate remaining at the end of the accessible proximal tubule were 54 ± 3, 64 ± 4, 70 ± 3, 79 ± 5, and 39 ± 5%, respectively. The concentration of magnesium and calcium in the tubule fluid rose significantly along the length of the proximal tubule. The tubule fluid bicarbonate concentration was measured by determination of total CO2 with microcalorimetry. The tubule fluid to blood bicarbonate ratio fell to 0.48 ± 0.06 at the late proximal tubule collection site, as the tubule fluid to ultrafiltrable chloride concentration ratio rose to 1.08 ± 0.02. Thus, bicarbonate is reabsorbed in preference to chloride in the superficial proximal tubule of the monkey, to provide a potential driving force for water and salt absorption. By the time the tubular fluid reached the distal tubule sampling site, most of the filtered sodium potassium, calcium, magnesium, and chloride was reabsorbed, suggesting the loop of Henle as a major site of ion reabsorption. Segments beyond the distal tubule collection site reabsorbed little of the delivered ions. These studies indicate that the function of the superficial nephron resembles that of species previously studied, except that calcium reabsorption is demonstrably diminished in the proximal convoluted tubule relative to other

ISSN:1420-4096    

DOI:10.1159/000173073

出版商:S. Karger AG    

年代:1986

数据来源: Karger

摘要:

The volume control of the syncytium of principal cells (as opposed to the mitochondria-rich cells) is largely confined to the movement of ions and water through the basolateral membrane. The apical membrane is nearly tight to water and ions except sodium. The basolateral membrane is normally tight to chloride, but its chloride channels open if the cells swell osmotically or if the membrane is depolarized. If the epithelium has lost KC1 during osmotic swelling, it is recovered by a basolateral cotransport of KNaCl2

ISSN:1420-4096    

DOI:10.1159/000173074

出版商:S. Karger AG    

年代:1986

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173076

出版商:S. Karger AG    

年代:1986

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000317492

出版商:S. Karger AG    

年代:1986

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000317493

出版商:S. Karger AG    

年代:1986

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000317494

出版商:S. Karger AG    

年代:1986

数据来源: Karger

ISSN:1420-4096    

DOI:10.1159/000173077

出版商:S. Karger AG    

年代:1986

数据来源: Karger