Biomedical subjects

R Lester

Publications and source records attributed to R Lester.

At least 19 recordsLinked to original sources

PubMed2026

First UK use of bacteriophage therapy with DAIR for chronic Staphylococcus aureus prosthetic joint infection.

BACKGROUND: Chronic Staphylococcus aureus prosthetic joint infection (PJI) remains difficult to manage when surgical revision and long-term antibiotics are not feasible. Bacteriophage therapy is emerging as a potential adjunct, though experience in orthopedic infections, particularly in the United Kingdom, is limited. CASE SUMMARY: We report the first UK case of intra-articular bacteriophage therapy administered alongside debridement, antibiotics, and implant retention (DAIR) for chronic methicillin-sensitive Staphylococcus aureus knee PJI. An 81-year-old man with multiple comorbidities developed persistent infection following revision knee arthroplasty, with recurrent sinus formation despite multiple surgical washouts and prolonged suppressive antibiotics. Major revision surgery and amputation were not viable options. Following a multidisciplinary review through the UK Clinical Phage Network, targeted phage therapy was pursued as salvage treatment. Phage susceptibility testing identified an active lytic phage (ISP). The patient underwent open DAIR with intra-articular phage administration, adjunctive local antibiotics, short-course intravenous antimicrobials, and subsequent oral suppressive therapy. Two further intra-articular phage doses were administered postoperatively. Initial sinus closure occurred, but recurrence developed within 4 weeks. At 18 months, symptoms were partially improved with better mobility and reduced inflammation, though one sinus tract persisted. No significant adverse effects were observed. Whole-genome sequencing of pretreatment isolates demonstrated a predominantly ST5 S. aureus genotype with conserved biofilm-associated virulence genes and limited antimicrobial resistance in addition to clonal diversification consistent with chronic biofilm infection. CONCLUSION: This case demonstrates the feasibility and safety of intra-articular phage therapy during DAIR in a UK setting but highlights biological, logistical, and pharmacological factors that may limit efficacy in advanced chronic PJI.

Staphylococcus aureus↗

PubMed1992

Biosynthesis and chemical synthesis of carboxyl-linked glucuronide of lithocholic acid.

The glucuronidation of lithocholic acid (LA) by phenobarbital-induced male Fischer 344 rat liver microsomes supplemented with UDP-glucuronic acid was studied. A single radioactive metabolite was formed and its structure was determined by high pressure liquid chromatography/particle beam/mass spectrometry (HPLC/PB/MS), both with and without prior methylation and acetylation of the sample. The reaction product was rigorously identified as the 1-O-acyl-beta-D-glucuronide of LA by comparison with a chemically synthesized standard. The chemical synthesis of the acyl glucuronide of LA was accomplished via a condensation reaction using benzyl 2,3,4-tri-O-benzyl-D-glucopyranuronate. The latter compound was prepared in two steps from benzyl 2,3,4-tri-O-benzyl-1-O-methyl-alpha-D-glucopyranuronate via the 1-O-acetyl derivative. The stereoselective beta coupling of LA with 2,3,4-tri-O-benzyl-D-glucopyranuronate was achieved by the Mitsunobu reaction, in the presence of the free hydroxyl function of LA, using triphenylphosphine and diisopropyl azodicarboxylate in THF followed by preparative TLC. The benzylic ester and ether groups were cleaved by hydrogenation with Pd on charcoal as the catalyst. Positive identification of the glucuronide was established by HPLC/PB/MS and 1H-NMR spectra. No side products formed by acyl migration were detected, but the free acyl glucuronide underwent rapid transesterification in methanol.

Acetylation↗

PubMed1992

Application of 5-azido-UDP-glucose and 5-azido-UDP-glucuronic acid photoaffinity probes for the determination of the active site orientation of microsomal UDP-glucosyltransferases and UDP-glucuronosyltransferases.

A new approach to determining the active site orientation of microsomal glycosyltransferases is presented which utilizes the photoaffinity analogs [32P]5-Azido-UDP-glucose ([32P]5N3UDP-Glc) and [32P]5-Azido-UDP-glucuronic acid ([32P]5N3UDP-GlcA). It was previously shown that both photoprobes could be used to photolabel UDP-glucose:dolichol phosphate glucosyltransferase (Glc-P-Dol synthase), as well as the family of UDP-glucuronosyltransferases in rat liver microsomes. The effects of detergents, proteases, and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) on the photolabeling of these enzymes were examined in intact rat liver microsomes. Photolabeling of Glc-P-Dol synthase by either photoprobe was the same in intact or disrupted vesicles, was susceptible to trypsin digestion, and was inhibited by the nonpenetrating inhibitor DIDS. Photolabeling of the UDP-glucuronosyltransferases by [32P]5N3UDP-GlcA was stimulated 1.3-fold in disrupted vesicles as compared to intact vesicles, whereas photolabeling of these enzymes by [32P]5N3UDP-Glc showed a 14-fold increase when vesicles were disrupted. Photolabeled UDP-glucuronosyltransferases were only susceptible to trypsin digestion in disrupted vesicles, and this was further verified by Western blot analyses. The results indicate a cytoplasmic orientation for access of UDP-sugars to Glc-P-Dol synthase and a lumenal orientation of most UDP-glucuronosyltransferases.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1992

Hepatic metabolism of 3-oxoandrost-4-ene-17 beta-carboxylic acid in the adult rat: formation of carboxyl-linked glucuronides both in vivo and in vitro.

The hepatic metabolism of 3-oxoandrost-4-ene-17 beta-carboxylic acid (etienic acid), a probable acidic catabolite of deoxycorticosterone, was investigated using rats prepared with an external biliary fistula. Metabolic products were identified by GC-MS after hydrolysis with beta-glucuronidase and by proton nuclear magnetic resonance after chromatographic purification of protected glucuronides. About 80% of the injected dose was secreted into bile in 20 hours. Three fully reduced etianic acids (3 alpha-hydroxy-5 alpha-, 3 beta-hydroxy-5 alpha-, 3 alpha-hydroxy-5 beta-androstan-17 beta-carboxylic acids) were identified as were several of their di- and trihydroxylated congeners. Glucuronides of these reduced and/or hydroxylated metabolites constituted over half of the recovered dose, with carboxyl-linked glucuronides predominating over 3-hydroxyl-linked glucuronides. The mode of glucuronidation correlated well with the ability of liver microsomes to form the corresponding compounds in vitro from the set of four 3,5-diastereomeric etianic acids.

Androstenes↗

PubMed1991

Synthesis and characterization of 5-azido-UDP-glucuronic acid. A new photoaffinity probe for UDP-glucuronic acid-utilizing proteins.

A new active site-directed photoaffinity analogue, [beta-32P]5-azido-UDP-glucuronic acid (UDP-GlcA), was enzymatically synthesized from [beta-32P]5-N3UDP-Glc using UDP-glucose dehydrogenase. The product was characterized by its mobility on ion exchange and two thin-layer chromatographic systems, by its UV absorbance at 288 nm, and the loss of this absorbance after UV irradiation of the compound. Photoincorporation of [beta-32P]5-N3UDP-GlcA into bovine liver UDP-Glc dehydrogenase (EC 1.1.1.22) was saturable with an apparent Kd of 12.5 microM, and was inhibited by the known active-site effectors UDP-GlcA, UDP-Glc, and UDP-xylose. When human liver microsomes with known UDP-glucuronosyltransferase (EC 2.4.1.17) activities were photolabeled with [beta-32P]5-N3UDP-GlcA, major photolabeled bands of 35-37 and 50-54 kDa were detected. When rat liver microsomes from phenobarbital-injected rats were photolabeled with [beta-32P]5-N3UDP-GlcA, there was a marked increase in photoincorporation of a 51-kDa protein as compared with control animals. Evidence is presented which suggests that the photolabeled 51-54-kDa proteins in the liver microsomes from both tissues are UDP-glucuronosyltransferase and that [beta-32P]5-N3UDP-GlcA represents a new alternative approach in the study of UDP-glucuronosyltransferase and other UDP-GlcA-utilizing enzymes.

Affinity Labels↗

PubMed1991

Taurine-conjugated bile acids act as Ca2+ ionophores.

The ionophoretic properties of several taurine-conjugated bile acids have been investigated in two experimental systems: in a two-phase bulk partitioning system and in proteoliposomes. In the former, a bile acid/Ca2+ complex was extracted into the bulk organic phase and had an experimental stoichiometry of 1.75. Extraction was specific for Ca2+ over Mg2+; Na+ and K+ did not compete with the extraction of Ca2+. In the second system, bile acids at concentrations as low as 5-100 molecules/vesicle lowered the steady-state Ca2+ gradient maintained by a reconstituted sarcoplasmic reticulum Ca(2+)-ATPase. The effect was not due to nonspecific membrane perturbation. In addition to releasing intravesicular Ca2+ in a transmembraneous process, bile acids caused partition of Ca2+/bile acid complexes into the hydrophobic core of the bilayer. In both experimental systems, the Ca2+ ionophoretic activity correlated well with the concentration and the hydrophobicity of the bile acid. Taurolithocholate was most active, with a significant effect measurable at 10 microM in either system. Since bile acid concentrations equal to those used in our experiments can occur in the blood in certain liver diseases, the results support the notion that bile acids can increase the intracellular Ca2+ concentration bypassing the regulatory systems that maintain cellular Ca2+ homeostasis.

Animals↗

PubMed1991

The anionic conjugates of bilirubin and bile acids stimulate ATP hydrolysis by S-(dinitrophenyl)glutathione ATPase of human erythrocyte.

These studies demonstrate that bilirubin-ditaurate (an analog of bilirubin-diglucuronide), lithocholic acid 3-O-sulfate, and lithocholic acid 3-O-glucuronide, which are believed to be transported from liver into bile through an active transport process stimulate ATP hydrolysis by purified dinitrophenylglutathione ATPase of human erythrocytes. The Km and Vmax values of the enzyme for these substrates are similar to those for dinitrophenylglutathione indicating the transport mechanisms for bilirubin conjugates, and anionic bile acid-conjugates from hepatocytes to bile and transport of GSH-conjugates from erythrocytes may be mediated by similar mechanisms.

Adenosine Triphosphatases↗

PubMed1991

Distinct forms of cytochrome P-450 are responsible for 6 beta-hydroxylation of bile acids and of neutral steroids.

Cytochrome P-450-dependent 6 beta-hydroxylation of bile acids in rat liver contributes to the synthesis of the quantitatively important pool of 6-hydroxylated bile acids, as well as to the detoxification of hydrophobic bile acids. The lithocholic acid 6 beta-hydroxylation reaction was investigated and compared with androstenedione 6 beta-hydroxylation. Differential responses of these two activities to inducers and inhibitors of microsomal P-450 enzymes, lack of mutual inhibition by the two substrates and differential inhibition by antibodies raised against several purified hepatic cytochromes P-450 were observed. From these results it was concluded that 6 beta-hydroxylation of lithocholic acid is catalysed by P-450 form(s) different from the subfamily IIIA cytochromes P-450 which are responsible for the bulk of microsomal androstenedione 6 beta-hydroxylation. Similar, but more tentative, results revealed that the 7 alpha-hydroxylation of lithocholic acid and of androstenedione may be also catalysed by distinct P-450 enzymes. The results indicate that cytochromes P-450 hydroxylating bile acids are distinct from analogous enzymes that carry out reactions of the same regio- and stereo-specificity on neutral steroids (steroid hormones). A comparison of pairs of cytochromes P-450 that catalyse the same reaction on closely related steroid molecules will help to define those structural elements in the proteins that determine the recognition of their respective substrates.

Androstenedione↗

PubMed1991

Purification and characterization of an ATPase from human liver which catalyzes ATP hydrolysis in the presence of the conjugates of bilirubin bile acids and glutathione.

An ATPase has been purified from the membrane fraction of human liver which catalyzes ATP in the presence of bilirubin ditaurate, lithocholic acid 3-O-sulfate and lithocholic acid 3-O-glucuronide as well as dinitrophenylglutathione and other glutathione conjugates. Its subunit Mr value (38,000) and immunological properties are similar to dinitrophenylglutathione ATPase of human erythrocytes. Kinetic constants of the enzyme for the conjugates of glutathione, bile acids and bilirubin are comparable indicating that this ATPase may mediate active transport of all these anionic conjugates in liver.

Adenosine Triphosphatases↗

PubMed1991

Castleman's disease associated with pemphigus vulgaris.

Castleman's disease is a rare, benign, lymphoproliferative disorder of unknown cause. The hyaline-vascular type is frequently associated with a localized mediastinal mass. The plasma-cell type is associated with constitutional symptoms, multicentric lymph node involvement, lymphoma development, and autoimmune disease-like laboratory abnormalities such as elevated erythrocyte sedimentation rate, anemia, and thrombocytopenia. We report a case of hyaline-vascular Castleman's disease associated with a cutaneous autoimmune disease, pemphigus vulgaris. We also reviewed the clinicopathologic features of four similar cases. Among these five reports of Castleman's disease, five patients had severe erosive stomatitis diagnosed as oral pemphigus, three had keratoconjunctivitis, and three had circulating pemphigus antibodies. All were young, ranging in age from 15 to 21 years, and four of the five were women. Two had hyaline-vascular Castleman's disease, whereas three had plasma-cell Castleman's disease. All five had surgical resection of the Castleman's disease mass. After surgery, remission of pemphigus vulgaris could be achieved with reduced dosages of steroids in all cases. In at least two cases steroid treatment could be completely discontinued. We postulate that an underlying immune dysfunction in Castleman's disease facilitates the expression of pemphigus.

Adult↗

PubMed1991

Urinary excretion of lithocholic acid and its conjugates by the bile duct-ligated rat.

The 3-O-glucuronide of lithocholic acid has been shown to be a potent cholestatic agent in rats. However, even after the onset of lithocholic acid glucuronide-induced cholestasis, little of the administered material was recovered in urine. To determine whether this phenomenon was related to the steroid moiety or the form of conjugation, small doses of radiolabeled lithocholic acid glucuronide, lithocholic acid, taurolithocholic acid and/or lithocholic acid sulfate were administered to rats with ligated bile ducts. Urinary excretion of isotope was followed for 24 hr and urinary metabolites of the administered compounds were identified by thin-layer chromatography. Lithocholic and taurolithocholic acids were slowly but relatively efficiently excreted in urine with 73% and 91% of the dose, respectively, recovered in urine over 24 hr. More than 80% of the label in urine from animals receiving these two compounds was in the form of taurine-conjugated beta-muricholic acid. In contrast, lithocholic acid 3-glucuronide and 3-sulfate were poorly excreted: 9% and 12% of the administered doses, respectively, were recovered in urine in 24 hr. Of the small amount of label in urine from rats given the glucuronide, 90% was identified as lithocholic and taurolithocholic acid glucuronides. When lithocholic acid sulfate was given, thin-layer chromatography of urine showed two peaks, which were tentatively identified as tauromurideoxycholic and taurolithocholic acid sulfates. More definitive identification was not possible because of the small amount of the administered dose excreted in urine in these forms.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Hepatic metabolism of short-chain bile acids. Inversion of the 3-hydroxyl group of isoetianic acid (3 beta-hydroxy-5 beta-androstane-17 beta-carboxylic acid) by the adult rat.

The stereospecificity of mechanisms for hepatic transport of short-chain bile acids has been examined by following the hepatic metabolism and biliary secretion of 3 beta-hydroxy-5 beta-androstane-17 beta-carboxylic acid (isoetianic acid) administered in two different labeled forms to rats prepared with an external biliary fistula. While 93% of the administered [2,2,4,4-3H]isoetianic acid was recovered in bile after 20 h, only 18% of a similar dose of [3 alpha-3H]isoetianic acid was secreted in bile over the same time period. The recovered radioactivity of the latter compound was mainly associated with bile water. With the [2,2,4,4-3H]isoetianic acid, the bulk of the biliary isotope was determined to be in the form of two glucuronide conjugates. Spectral analysis identified these metabolites as the hydroxyl-linked (major) and carboxyl-linked (minor) beta-glucuronides, not of the 3 beta-hydroxy compound administered, but of 3 alpha-hydroxy-5 beta-androstane-17 beta-carboxylic acid (etianic acid), i.e., the products of hydroxyl group inversion. It is concluded that isoetianic acid is efficiently cleared from plasma and conjugated with glucuronic acid after its epimerization to etianic acid. The prevalent, but not complete, loss of the 3-tritium atom and the retention of the 2- and 4-tritium atoms probably indicates a 3-oxo-5 beta-androstane-17 beta-carboxylic acid intermediate with partial return of the label via a limited labeled pool of reduced nicotinamide cofactor.

Androstanols↗

PubMed1990

The pathogenesis of cholestasis.

How does cholestasis develop when there is no obvious obstruction, destruction, or malformation of bile ducts? Recent findings on bile formation and flow are reviewed, and two models of intrahepatic cholestasis are presented: one of rapid onset, which is bile acid induced, and the other of slow onset, which is estrogen induced. Potential clinical correlations are discussed.

Bile↗

PubMed1990

Metabolism of lithocholic acid in the rat: formation of lithocholic acid 3-O-glucuronide in vivo.

Milligram amounts of [3 beta-3H]lithocholic (3 alpha-hydroxy-5 beta-cholanoic) acid were administered by intravenous infusion to rats prepared with a biliary fistula. Analysis of sequential bile samples by thin-layer chromatography (TLC) demonstrated that lithocholic acid glucuronide was present in bile throughout the course of the experiments and that its secretion rate paralleled that of total isotope secretion. Initial confirmation of the identity of this metabolite was obtained by the recovery of labeled lithocholic acid after beta-glucuronidase hydrolysis of bile samples. For detailed analysis of biliary metabolites of [3H]lithocholic acid, pooled bile samples from infused rats were subjected to reversed-phase chromatography and four major labeled peaks were isolated. After complete deconjugation, the two major compounds in the combined first two peaks were identified as murideoxycholic (3 alpha, 6 beta-dihydroxy-5 beta-cholanoic) and beta-muricholic (3 alpha, 6 beta, 7 beta-trihydroxy-5 beta-cholanoic) acids and the third peak was identified as taurolithocholic acid. The major component of the fourth peak, after isolation, derivatization (to the methyl ester acetate), and purification by high pressure liquid chromatography (HPLC), was positively identified by proton nuclear magnetic resonance as lithocholic acid 3 alpha-O-(beta-D-glucuronide). These studies have shown, for the first time, that lithocholic acid glucuronide is a product of in vivo hepatic metabolism of lithocholic acid in the rat.

Animals↗

PubMed1989

Effect of bile acids on calcium efflux from isolated rat hepatocytes and perfused rat livers.

The changes in intracellular Ca2+ concentration [( Ca2+]i) of hepatocytes induced by certain bile acids are biphasic: an initial increase is followed by a more gradual decrease. This latter decline in [Ca2+]i may be due to an efflux of Ca2+ across the plasma membrane. This hypothesis was tested by studying the effect of different bile acids on the efflux of 45Ca from preloaded rat hepatocytes and isolated perfused rat livers. The following bile acids were studied: cholic (C), ursodeoxycholic (UDC), chenodeoxycholic (CDC), and deoxycholic (DC) acids; their taurine (T) conjugates (TC, TUDC, TCDC, and TDC); and the taurine, sulfate (S), and glucuronide (Glu) derivatives of lithocholic acid (TLC, LS, TLS, and LGlu, respectively). At 0.3 mM, all bile acids except C, TC, TCDC, UDC, and TUDC significantly increased 45Ca efflux from preloaded hepatocytes without affecting cell viability. Dose-response studies revealed that the minimum effective concentration needed to induce 45Ca efflux was 0.06 mM for LS, 0.8 mM for TCDC, and 10 mM for TC. Efflux of 86Rb from preloaded hepatocytes was not significantly altered by 0.1 mM LS, indicating relative specificity for calcium. TDC and DC, but not TC, increased 45Ca efflux from preloaded perfused rat livers. These results showed that bile acids known to increase [Ca2+]i (CDC, DC, TDC, and TLC) also increased 45Ca efflux from hepatocytes and perfused livers and that efflux was also stimulated by LS, TLS, and LGlu. The extent of this efflux was related to the hydrophobicity of the steroid nucleus of the bile acid. It is speculated that bile acid-induced increases in [Ca2+]i activate the plasma membrane Ca2+ pump resulting in increased Ca2+ efflux.

Animals↗

PubMed1989

Defective biliary secretion of bile acid 3-O-glucuronides in rats with hereditary conjugated hyperbilirubinemia.

Biliary secretion of bile acid glucuronides was studied in control rats and in rats with a congenital defect in hepatobiliary transport of organic anions (GY rats). In control animals, hepatobiliary transport of [3H]lithocholic acid 3-O-glucuronide and [3H]cholic acid 3-O-glucuronide was efficient (greater than 95% in 1 h) and comparable to that of [14C]taurocholic acid. Secretion of both glucuronides was impaired in GY rats (24% and 71% at 1 h), whereas that of taurocholate was similar to control values. However, recovery of the glucuronides in bile was nearly complete within 24 h; virtually no radioactivity was found in urine. In control rats, biliary secretion of lithocholic acid 3-O-glucuronide, but not that of cholic acid 3-O-glucuronide or taurocholate, could be delayed by simultaneous infusion of dibromosulphthalein. In mutant rats, dibromosulphthalein infusion was also able to inhibit secretion of cholic acid 3-O-glucuronide. [3H]Hydroxyetianic acid, a C20 short-chain bile acid, was secreted by control rats as a mixture of 20% carboxyl-linked and 80% hydroxyl-linked (3-O-)glucuronide; secretion was very efficient (99% in 1 h). In GY rats, secretion was drastically impaired (16% at 1 h and 74% over a 24-h period). Initially, the mutant secreted more carboxyl- than hydroxyl-linked glucuronide, but the ratio reached that of control animals after 24 h. The rates of formation of both types of hydroxyetianic acid glucuronide by hepatic microsomes from mutant rats were similar or even slightly higher than those of control microsomes. These findings indicate that bile acid 3-O-glucuronides, but probably not carboxyl-linked glucuronides, are secreted into bile by a transport system shared with organic anions such as conjugated bilirubin and dibromosulphthalein, but different from that for amino acid-conjugated bile acids.

Androstanols↗

PubMed1989

Detoxification of lithocholic acid. Elucidation of the pathways of oxidative metabolism in rat liver microsomes.

The hydroxylation of lithocholic acid (3 alpha-hydroxy-5 beta-cholanoic acid) by adult male Sprague-Dawley rat liver microsomes supplemented with NADPH was studied. Metabolites were separated by a combination of thin-layer chromatography and high pressure liquid chromatography, both with and without prior methylation and acetylation of the samples. The resulting products were characterized by thin-layer, gas-liquid, and high pressure liquid chromatography by comparison with authentic bile acid standards; final structure determination was by proton nuclear magnetic resonance spectroscopy and by mass spectrometry. The following reaction products were found: 3 alpha, 6 beta-dihydroxy-5 beta-cholanoic acid (80% of total metabolites) and 3 alpha, 6 alpha-dihydroxy-5 beta-cholanoic, 3 alpha, 7 alpha-dihydroxy-5 beta-cholanoic, 3 alpha, 6 beta,7 beta-trihydroxy-5 beta-cholanoic, and 3 alpha-hydroxy-6-oxo-5 beta-cholanoic acids (less than or equal to 5% each). In addition, one unidentified trihydroxylic bile acid and several minor compounds were present. It is concluded that four different hydroxylation reactions of lithocholic acid, namely the predominant 6 beta as well as the minor 6 alpha, 7 alpha, and 7 beta hydroxylations, are catalyzed by rat hepatic microsomes; 7 beta-hydroxylation may occur only with dihydroxylated bile acids but not with lithocholate itself. The presence of the 6-oxo bile acid can be explained either by direct oxidation of a hydroxyl group by cytochrome P-450, or by the action of microsomal dehydrogenase(s) which could also catalyze the epimerization of hydroxyl groups via their oxidation. The results form the basis of a proposed scheme of the oxidative metabolism of lithocholic acid in rat liver microsomes.

Animals↗

PubMed1988

ATP-dependent Ca2+ uptake and Ca2+-dependent protein phosphorylation in basolateral liver plasma membranes.

ATP-dependent Ca2+ uptake was measured in vesicles of rat liver cell basolateral plasma membranes. Nucleotide-dependent uptake was specific for ATP and observed at pH 7.0 and 7.4/7.5 but not at pH 8.0. ATP-dependent Ca2+ transport was only observed in the presence of Mg2+. Kinetic analysis of ATP-dependent transport revealed an apparent Km in the submicromolar region. Addition of calmodulin and trifluoperazine had no effect on ATP-dependent uptake. A Ca2+-dependent, phosphorylated intermediate with the apparent molecular weight of 135,000 could be demonstrated in the basolateral plasma membranes. Phosphorylated intermediates with apparent molecular weights of 200,000 and 110,000 were demonstrated in microsomes and appeared to contaminate 'basolateral' membrane protein phosphorylation. The results suggest that a 135,000 molecular weight protein is a Ca2+-ATPase and the enzymatic expression of the liver cell basolateral membrane Ca2+ pump.

Animals↗