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B F Scharschmidt

Publications and source records attributed to B F Scharschmidt.

At least 73 records · Page 4Linked to original sources
PubMed1982

Chloride transport by intact rat liver and cultured rat hepatocytes.

Chloride is the predominant inorganic anion in bile, and it has been proposed that active chloride transport, possibly via a sodium-coupled mechanism, may contribute to that portion of canalicular bile formation not directly related to bile acid transport (bile acid-dependent bile formation or BAIBF). We have therefore examined the anion specificity of BAIBF using the isolated perfused rat liver and have studied sodium-chloride flux coupling and the sodium dependence of intracellular chloride content using 22Na and 36Cl transport by cultured rat hepatocytes. BAIBF by the isolated rat liver was unaltered by replacement of chloride with nitrate or benzenesulfonate but was significantly reduced by replacement of chloride with sulfate or thiocyanate. In cultured hepatocytes, sodium entry rate was reduced when chloride in the incubation medium was replaced by cyclamate, benzenesulfonate, or sulfate and mannitol but was unaffected when chloride was replaced by nitrate, gluconate, or thiocyanate. Conversely, chloride entry rate was decreased when sodium was replaced with choline but was unaffected when sodium was replaced by lithium or when ouabain was added to the medium. Thus no consistent evidence of sodium-chloride flux coupling was observed. Steady-state exchangeable intracellular chloride in the cultured hepatocytes was unaffected by ouabain or by replacement of sodium with choline and was increased when sodium was replaced by lithium. These findings indicate that basal BAIBF exhibits no specific chloride requirement. Although they do not exclude the possible existence in rat liver of sodium-coupled chloride transport, they provide no evidence that such a mechanism accounts for a major portion either of chloride transport by individual rat hepatocytes or of basal BAIBF by intact rat liver.

Animals↗
PubMed1982

Bile acid transport in cultured rat hepatocytes.

The mechanisms of bile acid uptake have been studied with primary monolayer cultures of rat hepatocytes. Hepatocytes were incubated with taurocholic acid (TC), glycocholic acid (GC), cholic acid (CA), glycochenodeoxycholic acid (GCDC), chenodeoxycholic acid (CDCA), deoxycholic acid (DOCA), lithocholic acid (LCA), or cholylglycylhistamine (CCH), a neutral bile acid derivative for 10 s to 60 min in medium containing sodium chloride, sodium chloride with 1 mM ouabain, or choline chloride. Cells were washed free of radioactive tracer, cell-associated radioactivity was quantitated, and bile acid uptake rates, kinetic parameters of uptake, and steady-state bile acid content were calculated. Two mechanisms for bile acid uptake were identified. Uptake of TC, GC, CA, and GCDC occurred predominantly via a sodium-dependent, ouabain-suppressible saturable mechanism, presumably sodium-coupled transport. Estimates of apparent Km and Vmax for these bile acids were TC, 33 micro M and 0.36 nmol . min-1 . mg prot-1; GC, 18 micro M and 0.22 nmol . min-1 . mg prot-1; CA, 13 micro M and 0.10 nmol . min-1 . mg prot; and GCDC, 6 micro M and 0.21 nmol . min-1 . mg prot, respectively. Uptake via this sodium-coupled mechanism exhibited considerable substrate selectivity. It was enhanced by increased ring hydroxylation and amino acid conjugation and decreased by further conjugation with a neutral histamine group (CGH). In contrast, uptake of CDCA, DOCA, LCA, and CGH occurred primarily via a nonsaturable sodium-independent mechanism, possibly simple diffusion. This mechanism accounted for only a small portion of uptake of TC, GC, CA, and GCDC at low bile acid concentrations. Nonsaturable bile acid uptake rates appeared to correlate with decane-buffer partition coefficients and to be related to bile acid structure.

Animals↗
PubMed1982

Effects of ion substitution on bile acid-dependent and -independent bile formation by rat liver.

To characterize the transport mechanisms responsible for formation of canalicular bile, we have examined the effects of ion substitution on bile acid-dependent and bile acid-independent bile formation by the isolated perfused rat liver. Complete replacement of perfusate sodium with choline and lithium abolished taurocholate-induced choleresis and reduced biliary taurocholate output by greater than 70%. Partial replacement of perfusate sodium (25 of 128 mM) by choline reduced bile acid-independent bile formation by 30% and replacement of the remaining sodium (103 mM) by choline reduced bile acid-independent bile formation by an additional 64%. In contrast, replacement of the remaining sodium (103 mM) by lithium reduced bile acid-independent bile formation by only an additional 20%, while complete replacement of sodium (128 mM) by lithium reduced bile formation by only 17%, and lithium replaced sodium as the predominant biliary cation. Replacement of perfusate bicarbonate by Tricine, a zwitterionic amino acid buffer, decreased bile acid-independent bile formation by greater than or equal to 50% and decreased biliary bicarbonate output by approximately 60%, regardless of the accompanying cation. In separate experiments, replacement of sodium by lithium essentially abolished Na,K-ATPase activity measured either as ouabain-suppressible ATP hydrolysis in rat liver or kidney homogenates, or as ouabain-suppressible 86Rb uptake by cultured rat hepatocytes. These studies indicate that bile acid(taurocholate)-dependent bile formation by rat liver exhibits a specific requirement for sodium, a finding probably attributable to the role(s) of sodium in hepatic sodium-coupled taurocholate uptake and/or in maintenance of Na,K-ATPase activity. The surprising finding that bile acid-independent bile formation was substantially unaltered by complete replacement of sodium with the permeant cation lithium does not appear to be explained by Na,K-ATPase-mediated lithium transport. Although alternative interpretations exist, this observation is consistent with the hypothesis that much of basal bile acid-independent bile formation is attributable to an ion pump other than Na,K-ATPase, which directly or indirectly mediates bicarbonate transport.

Animals↗
PubMed1981

Isolation of a rat liver plasma membrane fraction of probable canalicular origin. Preparative technique, enzymatic profile, composition, and solute transport.

A technique currently used for isolation of brush border membranes from renal and intestinal epithelium that involves vigorous tissue homogenization and sedimentation of non-luminal membranes in the presence of Mg2+ has been adapted to rat liver. Liver plasma membranes so prepared consisted almost exclusively of vesicles by electron microscopy, showed some contamination with endoplasmic reticulum and minimal contamination with mitochondria or Golgi by marker enzymes, were highly enriched in alkaline phosphatase, Mg2+-ATPase, and 5'-nucleotidase activity compared with homogenate, and showed little enrichment in (Na+, K+)-ATPase. Comparison of this enzymatic profile with cytochemical studies localizing (Na+, K+)-ATPase and alkaline phosphatase to the sinusoidal/lateral and canalicular membranes, respectively, suggested that these membranes were predominantly of canalicular origin. They had a lower (Na+ + K+)-ATPase specific activity, lower lipid content, and higher cholesterol to phospholipid molar ratio than a conventional plasma membrane preparation believed to be enriched in canaliculi. Moreover, it was possible to measure movement of D-[3H]glucose into an osmotically sensitive space bounded by these membrane vesicles.

Adenosine Triphosphatases↗
PubMed1981

Transport of sodium, chloride, and taurocholate by cultured rat hepatocytes.

Transport of sodium, chloride, and taurocholate was studied in primary cultures of adult rat hepatocytes incubated in a balanced electrolyte solution containing 150 mM NaCl, various concentrations of taurocholate, and (22)Na, (36)Cl, [(3)H]taurocholate, and 3-O-[(3)H]methyl-D-glucose. Lithium chloride, choline chloride, or Na(2)SO(4) and mannitol were substituted isotonically for NaCl in selected studies. The steady-state intracellular concentrations of exchangeable sodium and chloride averaged 6.5 mM and 30.1 mM, respectively. Ouabain reversibly increased intracellular sodium concentration. Chloride entry rate was about double that of sodium. Unlike sodium entry, chloride entry rate increased nonlinearly with increasing extracellular concentration. Taurocholate entry exhibited both saturable and nonsaturable components; the former accounting for virtually all taurocholate uptake at concentrations comparable to those found in vivo. Taurocholate was actively concentrated by the cultured cells, with the steady-state intracellular-to-extracellular concentration ratio decreasing from over 50 to about 1 as extracellular taurocholate concentration was increased from 10 muM to 4 mM. Both the saturable uptake component and concentrative taurocholate transport were virtually abolished by substitution of choline or lithium for sodium or by addition of ouabain. Taurocholate entry rate first increased in a sigmoid fashion and then decreased as extracellular sodium concentration was increased from 0 to 150 mM. Sodium entry rate increased in the presence of added taurocholate with an average of one sodium ion accompanying each taurocholate molecule into the cell. These findings indicate that sodium and chloride differ strikingly in their mechanism and rate of entry into cultured rat hepatocytes and in their intracellular concentration. Moreover, hepatocytes concentrate taurocholate by a sodium-coupled mechanism with an apparently equimolar transport stoichiometry.

Animals↗
PubMed1981

Effect of splenectomy of hepatic bilirubin clearance in patients with hereditary spherocytosis. Implications for the diagnosis of Gilbert's syndrome.

BRT and CBR were determined from studies of radiobilirubin kinetics in 14 patients undergoing splenectomy for hereditary spherocytosis. Studies were conducted both before and after the operation in order to assess the effects of the postsplenectomy fall in BRT on CBR. Splenectomy led to a doubling of the RBC-t1/2 from 13.0 +/- 1.7 (S.E.) days to 26.1 +/- 1.5 and a fall in BRT from 15.9 +/- 4.4 mg/kg/day to 4.3 +/- 0.9. In seven patients (group A) initially normal values for CBR were unaltered by surgery. In the remaining seven (group B), low preoperative values for CBR, suggestive of Gilbert's syndrome, uniformly improved after splenectomy, becoming normal in five patients. Nevertheless, family studies and reduced values for UDPGT activity supported the initial impression of concomitant Gilbert's syndrome in group B. These studies suggest the existence of a latent state for Gilbert's syndrome that, in some patients, may be unmasked by a hemolytic stress. As such, they have important implications for both pedigree analysis and incidence studies of this condition.

Adolescent↗
PubMed1979

Studies of relationship among bile flow, liver plasma membrane NaK-ATPase, and membrane microviscosity in the rat.

Liver plasma membrane (LPM) NaK-ATPase activity, LPM fluidity, and bile acid-independent flow (BAIF) were studied in rats pretreated with one of five experimental agents. Compared with controls, BAIF was increased 24.6% by thyroid hormone and 34.4% by phenobarbital, decreased by ethinyl estradiol, but unchanged by propylene glycol and cortisone acetate. Parallel to the observed changes in BAIF, NaK-ATPase activity also was increased by thyroid hormone (40.8%) and decreased by ethinyl estradiol (26.2%). In contrast, NaK-ATPase activity failed to increase after phenobarbital but did increase 36% after propylene glycol and 34.8% after cortisone acetate. Thus BAIF and NaK-ATPase activity did not always change in parallel. The NaK-ATPase K(m) for ATP was not affected by any of these agents.LPM fluidity, measured by fluorescence polarization using the probe 1,6-diphenyl-1,3,5-hexatriene, was found to be increased by propylene glycol, thyroid hormone, and cortisone acetate, decreased by ethinyl estradiol, and unaffected by phenobarbital. Thus in these cases, induced changes in LPM fluidity paralleled those in NaK-ATPase activity. In no case did Mg-ATPase or 5'-nucleotidase activities change in the same direction as NaK-ATPase, and the activity of neither of these enzymes correlated with LPM fluidity, thus indicating the selective nature of the changes in LPM enzyme activity caused by the agents. These findings indicate that LPM fluidity correlates with NaK-ATPase activity and may influence the activity of this enzyme. However, the nature of the role of LPM NaK-ATPase in bile secretion is uncertain and needs further study.

Animals↗
PubMed1979

Validation of a recording spectrophotometric method for measurement of membrane-associated Mg- and NaK-ATPase activity.

Conventional methods for determination of membrane-associated Mg- and NaK-ATPase activity typically involve a timed incubation of enzyme with ATP followed by measurement of released Pi. They are time-consuming, require a large amount of enzyme protein, and show considerable variability induplicate samples. These problems can be largely eliminated with a coupled enzyme assay in which formation of ADP by ATPase is coupled to NADH oxidation with the intermediate enzymes PK and LDH and the intermediate substrate phosphoenolpyruvate present in excess. NADH oxidation is continuously recorded at 340 nm, and NaK-ATPase represents the ouabain suppressible fraction of total ATPase. This method allows accurate determinatin of initial reaction rates which vary linearly with respect to enzyme protein. Furthermore, it eliminates the need to measure Pi and prevents accumulation of inhibitory ADP. In over 100 preparations of LPM prepared from rats pretreated with agents known to alter ATPase activity or exposed in vitro to ATPase inhibitors. ATPase activity by the coupled-enzyme assay paralleled results obtained with the conventional method. Moreover, the coupled-enzyme assay required less membrane protein, showed less variability in duplicate samples, required half the time, and also yielded accurate values in brain, kidney, and heart tissue. This improved assay should find broad application in the study of membrane ATPase as they relate to a variety of cellular functions.

Adenosine Triphosphatases↗
PubMed1978

The micellar sink: a quantitative assessment of the association of organic anions with mixed micelles and other macromolecular aggregates in rat bile.

Although the importance of mixed micelles in the solubilization and biliary excretion of lipids is established, little is known about a possible role of mixed micelles in the excretion of other biliary solutes. Ultrafiltration and ultracentrifugation techniques were used to investigate the interaction between substances that are excreted in bile and biliary mixed micelles. Substances (urea, erythritol, sucrose) excreted in bile at concentrations equal to, or less than, that in plasma did not show an association with mixed micelles, whereas substances (indocyanine green, iopanoic acid, rose bengal, unconjugated and conjugated sulfobromophthalein, and conjugated bilirubin) excreted in bile at high concentration relative to plasma did. The percentage of these latter substances in bile associated with micelles varied from 26 to 93% and was relatively independent of concentration. In addition to their association with mixed micelles, these test solutes formed self-aggregates that were stabilized primarily by ionic bonds, and only a small percentage (range = 0-5%) of these solutes were present in bile in the form of monomer or complexes small enough to pass a 5,000-mol wt membrane.These findings offer a possible explanation for the increase in sulfobromophthalein, bilirubin, and indocyanine green maximal biliary excretory rate produced by bile salt infusion, and suggest that the concentrative transport into bile of endogenous compounds and xenobiotics may result from their incorporation into mixed micelles and other macromolecular complexes.

Animals↗
PubMed1978

The lower esophageal ring and esophageal reflux.

Although the lower esophageal ring is an important cause of dysphagia in adults, its pathogenesis is unknown. To better define the relationship between the lower esophageal ring and esophageal reflux, we analyzed, retrospectively, the records of 18 hospitalized patients with radiologically demonstrated rings (16 confirmed by endoscopy and/or surgery). In 16 of these patients, evidence of esophageal reflux including at least one of the following was present: overt esophagitis noted at endoscopy or surgery (14 cases), histologic evidence of esophagitis (3 cases), and/or symptoms of pyrosis or free reflux (13 cases). These findings suggest that 1. reflux is frequently associated with lower esophageal rings and may play a role in their pathogenesis; 2. the radiologic finding of a ring should serve as a clue to the possibility of esophageal reflux and 3. long-term control of dysphagia in these patients may depend upon control of the associated reflux as well as mechanical disruption of the ring.

Adult↗
PubMed1978

Studies of the kinetics of purified conjugated bilirubin-3H in the rat.

Radio-labeled conjugated bilirubin was purified from rat bile by affinity chromatography. Following the intravenous injection of tracer doses of this material, the initial fractional plasma disappearance rate of conjugated bilirubin-3H in the normal Sprague-Dawley rat was found to be approximately 50% faster than that for unconjugated bilirubin-3H (0.51 +/- 0.94 [SE] vs. 0.35 +/- 0.02 min.-1; P less than .001). Hepatic recovery studies in the rat indicated that, over the first four minutes after injection, disappearance of cholephilic anions from plasma is accounted for almost entirely by hepatic uptake. Hence, these studies demonstrate that hepatic uptake of conjugated bilirubin is substantially faster than that of unconjugated bilirubin. Net hepatic clearance of conjugated bilirubin in normal rats was three-fold greater than that of unconjugated bilirubin (0.94 +/- 0.16 vs. 0.30 +/- 0.03 ml./min./100 gm. body weight; P less than .001), presumably reflecting both the more rapid hepatic uptake and the ability of the former pigment to by-pass the conjugation step. Hepatic uptake of conjugated bilirubin was shown to be inhibited by unconjugated bilirubin, sulfobromophthalein and indocyanine green but not by glycocholate. These observations cannot be explained by simple diffusion and suggest that the hepatic uptake mechanism for conjugated bilirubin is the same as that for the unconjugated pigment.

Animals↗
PubMed1977

The natural history of hypertrophic gastrophy (Menetrier's disease). Report of a case with 16 year follow-up and review of 120 cases from the literature.

We describe a 33 year old man who presented with epigastric pain, weight loss and hematemesis. Roentgenograms of the upper gastrointestinal tract and endoscopy demonstrated giant rugal folds, and the diagnosis of hypertrophic gastropathy was confirmed by operative biopsy. This patient's symptoms and abnormalities noted on the roentgenograms persisted until his death 16 years later. Postmortem examination confirmed the persistence of hypertrophic gastropathy and revealed, in addition, a hepatocellular carcinoma metastatic to the stomach and regional lymph nodes. A review of 120 previously reported cases of hypertrophic gastropathy with special attention to its natural history indicates that the chronic nature of this patient's illness is typical. In addition, the chance of gastric carcinoma developing in these patients is appreciable. Since the reported long-term results of operative therapy appear favorable, patients with persistent and sufficiently distressing symptoms should be considered for gastric resection.

Adult↗
PubMed1977

The use of calcium chelating agents and prostaglandin E to eliminate platelet and white blood cell losses resulting from hemoperfusion through uncoated charcoal, albumin-agarose gel, and neutral and cation exchange resins.

Hemoperfusion through adsorbents such as charcoal, cation exchange (e.g., AG 50W-X8) and uncharged (e.g., XAD-2) resins, and albumin-agarose gel (AAG) has been proposed for use in patients with hepatic failure. However, the loss of white blood cells and, particularly, platelets caused by each of these adsorbents remains a major deterrent to their clinical use. In vitro studies demonstrate that addition of citrate, ethylenediamine tetraacetate (EDTA), or oxalate to heparinized human blood eliminated this loss of formed blood elements during hemoperfusion. The improvement in postperfusion platelet counts (per cent of preperfusion values) produced by citrate were XAD-2, 13 leads to 95 per cent; AG 50W-X8, 10 leads to 94 per cent; AAG, 17 leads to 94 per cent; and charcoal, 44 leads to 96 per cent. Prostaglandin E1 in high doses (5 mug/ml.) markedly reduced platelet losses. Lower doses were less uniformly effective. Three young rhesus monkeys were hemoperfused for 160 minutes with columns containing AAG, XAD-2, and charcoal. During the first 80 minutes, citrate and calcium were infused into the column inflow and outflow lines respectively. For all three adsorbents, average platelet counts in the monkeys (115 per cent) and column effluent (95 per cent) were unchanged from preperfusion control values during the first 80 minutes but fell promptly to 13 and 7 per cent, respectively, after the citrate infusion was stopped. Each of the monkeys tolerated the procedure without ill effects. Use of a system analogous to that described here may facilitate clinical application of the technique of hemoperfusion through a variety of adsorbents.

Albumins↗
PubMed1976

The effect of repeated phlebotomy on bilirubin turnover, bilirubin clearance and unconjugated hyperbilirubinaemia in the Crigler-Najjar syndrome and the jaundiced Gunn rat: application of computers to experimental design.

1. A multicompartmental model of erythrokinetics and bilirubin production has been developed to predict the consequences of chronic phlebotomy on daily bilirubin turnover. 2. Control values for four physiological variables including bilirubin turnover were determined in a 20-year-old woman with type I congenital nonhaemolytic jaundice (Crigler-Najjar syndrome). With these base-line data, the model predicted the following changes during phlebotomy: a 34% fall in bilirubin turnover; a 240% increase in the haemoglobin content of bone-marrow erythroid precursors; a 25% fall in the half-life of 51Cr-labelled erythrocytes; a characteristic alteration of the erythrocyte survival curve after labelling with [2-14C]glycine. 3. On the assumption, previously validated in normal volunteer subjects and patients with Gilbert's syndrome, that hepatic bilirubin clearance was independent of turnover and would therefore remain unchanged, a fall in plasma unconjugated bilirubin concentration during phlebotomy from 436 to 282 mumol/1 was expected. 4. Accordingly, the patient underwent phlebotomy 350 ml/week for 2 months, and 500 ml/week during an additional 3 months. Appropriate studies during phlebotomy confirmed each of the predictions in paragraph 2 above. In particular, turnover fell by 31%. Unexpectedly, plasma unconjugated bilirubin remained essentially unchanged. Analogous results were observed in phlebotomized jaundiced Gunn rats. 5. Kinetic studies in both the patient and the rats demonstrated that the failure of plasma unconjugated bilirubin to fall in parallel with bilirubin turnover resulted from a prolongation of the terminal half-life of radioactively labelled bilirubin and a fall in bilirubin clearance in every instance. 6. These studies indicate that (a) in congenital non-haemolytic jaundice, bilirubin clearance is uniquely influenced by bilirubin turnover and (b) compartmental modelling and kinetic studies are useful for predicting and interpreting the results of both physiological experiments and experimental therapeutic regimens.

Adult↗