The role of sulfhydryl groups in human neutrophil adhesion, movement and particle ingestion

Recent studies have suggested that ectosulfhydryl groups may play a role in cell contact phenomena. We have studied the possible role of ecto- and endosulfhydryl groups in the morphology, adhesiveness, random and directed (chemotaxis) motility and phagocytosis of human polymorphonuclear neutrophils. The rapidly penetrating sulfhydryl binding reagents HgCl₂ and NEM inhibited adhesiveness, motility and phagocytosis when studied at > 0.1 mM in plasma or > 0.01 mM in buffer. The difference in inhibitory concentration was shown to be due to the difference in albumin content of the two media. D-cysteine prevented the effect of HgCl₂ and NEM on cell morphology, adhesiveness, motility and phagocytosis indicating that their effects were on cell sulfhydryl groups. PCMBS, a very slowly penetrating organic mercurial, had no effect on neutrophil morphology, adhesiveness, motility or phagocytosis. However, PCMBS inhibited platelet aggregation, assuring its potency. These studies indicate that ectosulfhydryl groups are either not present or not participants in the maintainence of structure and functions of human neutrophilic granulocytes.     

EFFECTS OF SULFHYDRYL REAGENTS ON BRAIN MICROTUBULE-ASSOCIATED ATPase ACTIVITY IN VITRO

Abstract— The effects of two sulfhydryl reagents, PCMBS ( p -chloromercuribenzene sulfonic acid) and NEM ( N -ethylmaleimide) on microtubule-associated Mg²⁺ -and Ca²⁺ -ATPase activity were studied in a MTP (microtubule proteins) preparation and in a MAP (microtubule-associated proteins) fraction. In the MTP preparation at pH 6.8, PCMBS stimulated the Mg²⁺ -ATPase activity at low concentrations and inhibited at higher, whereas the Ca²⁺ -ATPdse activity was only inhibited. NEM affected the activity in a similar way. At pH 8.0 PCMBS was only inhibitory. NEM showed stimulatory effects over a broader concentration range.
Preincubation in the presence of ATP counteracted the stimulatory effects of both PCMBS and NEM on Mg²⁺ -ATPase at pH 6.8.
In the MAP fraction at pH 6.8 PCMBS and NEM caused similar but less pronounced effects on the Mg²⁺ -and Ca²⁺ -ATPase.
The results show that brain microtubule-associated ATPase activity is similar to dynein and myosin ATPases with respect to biphasic alteration by sulfhydryl reagents.     

Lectin-mediated agglutination of murine lymphoma cells. Cell surface deformability and reversibility of agglutination by saccharides

Agglutination of S49 mouse lymphoma cells by Ricinus communis I agglutinin can be reversed by the competing haptenic saccharide, lactose, soon after agglutination, but after further incubation in the absence of lectin the agglutination reaction could not be reversed by lactose and the cells remained as multicell aggregates. The irreversibility of S49 cell agglutination was time, temperature and lectin concentration dependent and its onset correlated with ultrastructurally observed deformation of adjacent cell surfaces and an increase in the proportion of adjacent cell surface areas in close apposition within multicell aggregates. Pretreatment of S49 cells with cytochalasin B or cytochalasin B plus vinblastine enhanced R. communis I agglutinin-mediated agglutination, while vinblastine alone and fluoride plus azide had essentially no effect. When drug-treated cells were agglutinated and then incubated in lectin-free drug-containing media for various times prior to lactose addition, the drug effects were more pronounced. Cytochalasin B alone or with vinblastine inhibited lactose reversal of S49 cell agglutination compared to the drug-free controls, while fluoride plus azide enhanced hapten reversibility. Electron microscopic analysis revealed that the onset of agglutination irreversibility correlated with cell surface deformation in the drug-treated cells. Cell aggregates that were more readily reversible by lactose (fluoride plus azide) were unchanged or less deformed, while S49 aggregates treated with cytochalasin B plus vinblastine were more deformed compared to controls without drugs. These experiments suggest a role for cell surface deformability as an important secondary effect during lectin-mediated cell agglutination of 849 lymphoma cells.     

Lectin-mediated agglutination of murine lymphoma cells. Cell surface deformability and reversibility of agglutination by saccharides.

Agglutination of S49 mouse lymphoma cells by Ricinus communis I agglutinin can be reversed by the competing haptenic saccharide, lactose, soon after agglutination, but after further incubation in the absence of lectin the agglutination reaction could not be reversed by lactose and the cells remained as multicell aggregates. The irreversibility of S49 cell agglutination was time, temperature and lectin concentration dependent and its onset correlated with ultrastructurally observed deformation of adjacent cell surfaces and an increase in the proportion of adjacent cell surface areas in close apposition within multicell aggregates. Pretreatment of S49 cells with cytochalasin B or cytochalasin B plus vinblastine enhanced R. communis I agglutinin-mediated agglutination, while vinblastine alone and fluoride plus azide had essentially no effect. When drug-treated cells were agglutinated and then incubated in lectin-free drug-containing media for various times prior to lactose addition, the drug effects were more pronounced. Cytochalasin B alone or with vinblastine inhibited lactose reversal of S49 cell agglutination compared to the drug-free controls, while fluoride plus azide enhanced hapten reversibility. Electron microscopic analysis revealed that the onset of agglutination irreversibility correlated with cell surface deformation in the drug-treated cells. Cell aggregates that were more readily reversible by lactose (fluoride plus azide) were unchanged or less deformed, while S49 aggregates treated with cytochalasin B plus vinblastine were more deformed compared to controls without drugs. These experiments suggest a role for cell surface deformability as an important secondary effect during lectin-mediated cell agglutination of S49 lymphoma cells.     

Antibody-dependent, eosinophil-mediated damage to 51Cr-labeled schistosomula of Schistosoma mansoni: effect of metabolic inhibitors and other agents which alter cell function.

The effect of drugs known to inhibit different metabolic pathways or cell functions on antibody-dependent, eosinophil-mediated damage to schistosomula was determined. Eosinophil-mediated damage was completely inhibited by cytochalasin B, inhibitors of glycolysis, aminophylline, and treatment of cells with diazotized sulfanilic acid and tosyl-lysyl-chloromethyl ketone. The effects of cytochalasin and 2-deoxyglucose were reversible. On the other hand, eosinophil-mediated damage was unaffected by agents which inhibit DNA replication, protein synthesis, oxidative respiration, prostaglandin synthesis, and microtubule aggregation. The findings suggest that alteration of the cell surface membrane and microfilaments prevents damage by interfering with cell-target interactions, that energy derived from glycolysis is required for cytotoxicity, that cell-associated esterases are probably involved, and that cytotoxicity may be modulated by cyclic nucleotides. Some of the attributes of eosinophils that allow it and not other cells to mediate this reaction are discussed.     

Light-induced chloroplast movements in Lemna trisulca. Identification of the motile system

In mesophyll cells of the water plant Lemna trisulca L. chloroplasts redistribute in response to blue light. In the present study it is shown that an actin depolymerizing agent cytochalasin D, a crosslinker of actin subunits in F-actin m-maleimidobenzoic acid N-hydroxysuccinimide ester (MBS) as well as N-ethylmaleimide (NEM)—a sulfhydryl group reagent, are potent inhibitors of these blue light-induced chloroplast movements in Lemna. Extraction with cold, buffered glycerol solution preserves light-induced chloroplast arrangements within cells producing permeabilized cell models. ‘Reactivation’ of these cell models by Mg-ATP results in remarkable movements which can be inhibited by treatment with NEM and cytochalasin D. Immunofluorescence microscopy demonstrates that a component which is associated with isolated Lemna chloroplasts cross-reacts with antibodies directed against bovine myosin. These results indicate that a contractile actomyosin system is involved in blue light-induced chloroplast movements in Lemna and a putative motor protein, similar to myosin, is associated with the surface of Lemna chloroplasts.     

Dependence of fluid-phase pinocytosis in arterial smooth-muscle cells on temperature, cellular ATP concentration and the cytoskeletal system.

125I-labelled poly(vinylpyrrolidone) was used as a marker of fluid-phase pinocytosis in cultured pig arterial smooth-muscle cells. The rate of pinocytosis was temperature-dependent. A decrease in cellular ATP concentrations as a result of inhibition of either glycolysis or oxidative phosphorylation was associated with a similar decrease in pinocytosis. A microfibrillar-disruptive agent, cytochalasin B, caused a concentration-dependent stimulation of pinocytosis, whereas the microtubular-disruptive agents colchicine and vinblastine decreased pinocytosis to approximately half of control values at all concentrations used. These results indicate that fluid-phase pinocytosis in smooth-muscle cells is dependent on a continuing supply of energy and the integrity of the microtubules. Furthermore, microfilaments appear to exert a certain degree of constraint on pinocytosis, possibly by restricting invagination of the plasma membrane.     

P2X(7) is a scavenger receptor for apoptotic cells in the absence of its ligand, extracellular ATP

Phagocytosis of apoptotic cells is essential during development and tissue remodeling. Our previous study has shown that the P2X(7) receptor regulates phagocytosis of nonopsonized particles and bacteria. In this study, we demonstrate that P2X(7) also mediates phagocytosis of apoptotic lymphocytes and neuronal cells by human monocyte-derived macrophages under serum-free conditions. ATP inhibited this process to a similar extent as observed with cytochalasin D. P2X(7)-transfected HEK-293 cells acquired the ability to phagocytose apoptotic lymphocytes. Injection of apoptotic thymocytes into the peritoneal cavity of wild-type mice resulted in their phagocytosis by macrophages, but injection of ATP prior to thymocytes markedly decreased this uptake. In contrast, ATP failed to inhibit phagocytosis of apoptotic thymocytes in vivo by P2X(7)-deficient peritoneal macrophages. The surface expression of P2X(7) on phagocytes increased significantly during phagocytosis of either beads or apoptotic cells. A peptide screen library containing 24 biotin-conjugated peptides mimicking the extracellular domain of P2X(7) was used to evaluate the binding profile to beads, bacteria, and apoptotic cells. One peptide showed binding to all particles and cell membrane lipids. Three other cysteine-containing peptides uniquely bound the surface of apoptotic cells but not viable cells, whereas substitution of alanine for cysteine abolished peptide binding. Several thiol-reactive compounds including N-acetyl-L-cysteine abolished phagocytosis of apoptotic SH-SY5Y cells by macrophages. These data suggest that the P2X(7) receptor in its unactivated state acts like a scavenger receptor, and its extracellular disulphide bonds play an important role in direct recognition and engulfment of apoptotic cells.     

Sodium fluoride reveals multiple pathways for regulation of surface expression of the C3b/C4b receptor (CR1) on human polymorphonuclear leukocytes

We have examined the effects of NaF on C3b receptor (CR1) expression and function in human polymorphonuclear leukocytes (PMN). Plasma membrane expression of CR1 was determined with a monoclonal antibody (3D9); CR1 function was assessed with erythrocytes bearing C3b (EC3b) or C3b oligomers prepared with avidin and biotin. NaF inhibited in a dose-dependent manner CR1-mediated phagocytosis and NaF inhibited f-met-leu-phe or phorbol dibutyrate-induced increases in CR1 expression, with 50% inhibition at 5 mM NaF. Increased plasma membrane expression of CR3 induced by f-met-leu-phe also was inhibited by NaF. However, increased CR1 and CR3 expression due to incubation at 37 degrees C were unaffected by 10 mM NaF. Incubation of PMN with 10 mM NaF depleted 80% of intracellular adenosine triphosphate (ATP) after 10 min. However, inhibition of CR1 function was unrelated to ATP level, inasmuch as normal increases in CR1 expression and in phagocytosis occurred 20 min after removal of NaF, whereas ATP levels remained below 25% of normal. Strikingly, internalization of soluble oligomeric C3b ligands was unaffected by 10 mM NaF, which completely inhibited phorbol dibutyrate-induced CR1 internalization and EC3b phagocytosis. We conclude that there are two different mechanisms for increasing plasma membrane expression of CR1, one of which is inhibitable by NaF. Moreover, there are two distinct pathways of CR1 internalization which can also be distinguished by their sensitivity to NaF.     

Modifying effect of vinblastine on superoxide anion production by membrane perturbing agents in polymorphonuclear leukocytes

Superoxide anion production in peritoneal polymorphonuclear leukocytes obtained from guinea pigs was stimulated by in vitro treatment with membrane-perturbing agents, such as cytochalasin D, concanavalin A, phorbol myristate acetate, myristate, digitonin, and NaF. Vinblastine modified these stimulating effects on the superoxide anion production, but its modifying effect was not uniform. The effect of cytochalasin D was stimulated by vinblastine at the concentration of 10(-5)-10(-7) M, whereas it was inhibited at the concentration of 10(-4) M. At 10(-4)-10(-5) M, vinblastine was inhibitory to the effect of concanavalin A, and lower concentrations had no significant effect. Stimulation of the superoxide anion production by phorbol myristate acetate and myristate was further enhanced by vinblastine at any concentration in the range of 10(-4)-10(-8) M with peaks at 10(-6) and 10(-5) M, respectively. Vinblastine had little effect on the stimulation of the superoxide anion production by digitonin and NaF throughout the concentration range examined. The mechanism of the interaction of these membrane-perturbing stimulants and vinblastine is discussed.     

Active target cell processes, possibly involving receptor-mediated endocytosis, are critical for expression of cytotoxicity by natural killer cell-derived cytolytic factor

Inhibitors of energy metabolism, 2-deoxyglucose and cyanide were shown to inhibit NKCF-mediated lysis of L929 target cells at the same molar concentrations that effectively inhibited cellular ATP levels and the toxic effects of pseudomonas toxin A. In addition, inhibitors of receptor-mediated endocytosis, cytochalasin B, a microtubule disrupter, and trifluoperazine, an inhibitor of clathrin-coat formation, inhibited NKCF-mediated lysis and expression of pseudomonas toxin activity, but had little effect upon cellular ATP. Lysomotropic agents chloroquine, ammonium chloride, and dansylcadavarine also inhibited both NKCF-mediated lysis and pseudomonas toxin activity. These results are similar to those involving diphtheria toxin and the plant toxins abrin, modeccin, and ricin, whose mode of action involves inhibition of protein synthesis following receptor-mediated endocytosis. However, it was determined that NKCF did not cause a decrease in the rate of protein synthesis up to the time of cell death. These results suggest that active target cell processes (possibly involving receptor-mediated endocytosis of NKCF) must occur for target cell lysis to be completed.     

Effects of cytochalasin B, colchicine and vincristine on the metabolism of isolated fat-cells

1. Colchicine and vincristine only slightly inhibit the metabolism of glucose to CO(2) and lipids by isolated fat-cells. 2. Prolonged incubation with these agents causes no further inhibition. 3. Cytochalasin B, however, inhibits glucose metabolism to both CO(2) and lipids in fat-cells. 4. However, at a concentration that causes a strong inhibition of glucose metabolism cytochalasin B is without effect on the metabolism of pyruvate, lactate or arginine to these end products. The uptake of labelled alpha-aminoisobutyrate is likewise not modified. Similarly it does not affect release of glycerol or free fatty acid, or the actions of adrenaline, insulin or caffeine on these parameters. At 10mug/ml it slightly lowers ATP concentrations, an effect that does not occur at 2mug/ml. 5. The transport of fructose into adipocytes by a specific fructose-transport system is also not affected by the agent, but the uptake of 2-deoxyglucose is strongly inhibited. It is concluded that cytochalasin B may specifically inhibit the glucose-transport system of isolated fat-cells. 6. Cytochalasin A has a much weaker action than cytochalasin B on glucose metabolism.     

Glucose requirement for postischemic recovery of perfused working heart

The quantitative importance of glycolysis in cardiomyocyte reenergization and contractile recovery was examined in postischemic, preload-controlled, isolated working guinea pig hearts. A 25-min global but low-flow ischemia with concurrent norepinephrine infusion to exhaust cellular glycogen stores was followed by a 15-min reperfusion. With 5 mM pyruvate as sole reperfusion substrate, severe contractile failure developed despite normal sarcolemmal pyruvate transport rate and high intracellular pyruvate concentrations near 2 mM. Reperfusion dysfunction was characterized by a low cytosolic phosphorylation potential [( ATP]/[( ADP][Pi]) due to accumulations of inorganic phosphate (Pi) and lactate. In contrast, with 5 mM glucose plus pyruvate as substrates, but not with glucose as sole substrate, reperfusion phosphorylation potential and function recovered to near normal. During the critical ischemia-reperfusion transition at 30 s reperfusion the cytosolic creatine kinase appeared displaced from equilibrium, regardless of the substrate supply. When under these conditions glucose and pyruvate were coinfused, glycolytic flux was near maximum, the glyceraldehyde-3-phosphate dehydrogenase/3-phosphoglycerate kinase reaction was enhanced, accumulation of Pi was attenuated, ATP content was slightly increased, and adenosine release was low. Thus, glucose prevented deterioration of the phosphorylation potential to levels incompatible with reperfusion recovery. Immediate energetic support due to maximum glycolytic ATP production and enhancement of the glyceraldehyde-3-phosphate dehydrogenase/3-phosphoglycerate kinase reaction appeared to act in concert to prevent detrimental collapse of [ATP]/[( ADP][Pi]) during creatine kinase dysfunction in the ischemia-reperfusion transition. Dichloroacetate (2 mM) plus glucose stimulated glycolysis but failed fully to reenergize the reperfused heart; conversely, 10 mM 2-deoxyglucose plus pyruvate inhibited glycolysis and produced virtually instantaneous de-energization during reperfusion. The following conclusions were reached. (1) A functional glycolysis is required to prevent energetic and contractile collapse of the low-flow ischemic or reperfused heart (2). Glucose stabilization of energetics in pyruvate-perfused hearts is due in part to intensification of glyceraldehyde-3-phosphate dehydrogenase/3-phosphoglycerate kinase activity. (3) 2-Deoxyglucose depletes the glyceraldehyde-3-phosphate pool and effects intracellular phosphate fixation in the form of 2-deoxyglucose 6-phosphate, but the cytosolic phosphorylation potential is not increased and reperfusion failure occurs instantly. (4) Consistent correlations exist between cytosolic ATP phosphorylation potential and reperfusion contractile function. The findings depict glycolysis as a highly adaptive emergency mechanism which can prevent deleterious myocyte deenergization during forced ischemia-reperfusion transitions in presence of excess oxidative substrate.     

Effects of antiphagocytic agents on penetration of Eimeria magna sporozoites into cultured cells.

Madin-Darby Bovine Kidney cells were treated with sodium flouride, iodoacetate, and 2-deosyglucose, reagents that block glycolysis, and thus reduce phagocytosis. Sporozoites readily entered cells whose ATP stores were largely depleted. They also entered cells treated with colchicine, colcemid, and vinblastine. These latter agents did not inhibit sporozite motility after 6 hr incubation. Cytochalasin B prevented penetration of cells by inhibiting the motility of sporozoites. This effect was reversible. Warm sporozoites entered cold cells 4 times more radily than cold sporozoites into warm cells. The above findings suggest that phagocytosis is not the mechanism for entry of E. magna sporozoites into cultured cells, but that sporozoite motility is of primary importance.     

Fibroblast spreading and phagocytosis: similar cell responses to different-sized substrata

Experiments were carried out to test the hypothesis that cell spreading and phagocytosis are similar cell responses to different-sized substrata. The following morphological and biochemical studies provided evidence for this supposition. Cells phagocytosed 1.09-micron and 5.7-micron latex beads, but were unable to completely ingest 15.8-micron or 25.7-micron beads. With the larger beads, the cells spread around the bead surfaces with an appearance typical of cells spread on culture dishes. Biochemical studies with cytochalasin D, azide, and iodoacetate, as well as temperature-dependence studies, demonstrated similar responses of cell spreading and phagocytosis to these treatments. Similar cell surface receptors were involved in cell spreading and phagocytosis based upon experiments using antibodies to baby hamster kidney (BHK) cell wheat germ agglutinin receptors. And finally, BHK cell variants with defective plasma fibronectin (pFN) receptors were unable to spread on pFN-coated dishes or ingest pFN-coated beads. Evidence also is presented concerning the "contact" process in cell adhesion. It was found that azide and low temperature inhibited cell attachment per se but did not block fibronectin-receptor interactions based upon cell binding of pFN-coated beads. A possible explanation for the contact process is presented based upon the resistance of cells and beads to shear forces.     

INHIBITION OF PHAGOCYTOSIS AND PLASMA MEMBRANE MOBILITY OF THE CULTIVATED MACROPHAGE BY CYTOCHALASIN B : Role of Subplasmalemmal Microfilaments

Functional and morphologic effects of cytochalasin B on the cultivated macrophage were examined to determine the basis for plasma membrane movements of the type required for endocytosis and/or spreading on a substratum. Inhibition of phagocytosis and changes in cell shape by cytochalasin B exhibited nearly identical dose-response curves requiring 2–5 x 10^-6 M and 1–2 x 10^-5 M cytochalasin B to inhibit these functions by 50% and 100%, respectively. In contrast, hexose transport was ten times more sensitive to the drug requiring 2–3 x 10^-7 M cytochalasin B to achieve 50% inhibition of 2-deoxyglucose uptake. Inhibition of phagocytosis and changes in cell shape could not be explained solely by drug effects on hexose transport. Analysis of serial thin sections showed that cytochalasin B doses inhibitory for hexose transport had no effect on distribution or organization of either of the two subplasmalemmal microfilament types. However, cytochalasin B concentrations (2.0 x 10^-5 M) that inhibited phagocytosis and altered cell shape disorganized and/or disrupted oriented bundles of 40–50-Å subplasmalemmal microfilaments, but had no effect on the microfilamentous network. Comparative dose-response studies showing positive correlations among cytochalasin B effects on phagocytosis, changes in cell shape, and alterations in oriented subplasmalemmal microfilament bundles provide additional support for the hypothesis that microfilamentous structures play a role in translocation of plasma membrane required for endocytosis and cell motility.     

Phloem loading in Vicia faba leaves: Effect of N-ethylmaleimide and parachloromercuribenzenesulfonic acid on H+ extrusion,K+ and sucrose uptake

The effects of a penetrating (NEM) and a non-penetrating (PCMBS) sulfhydryl-specific reagent on proton extrusion, ⁸⁶Rb and [U-¹⁴C]sucrose uptake by Vicia faba leaves have been studied. Proton extrusion was strongly or completely inhibited by 0.1 mM NEM. ⁸⁶Rb and [U-¹⁴C]sucrose uptake were markedly reduced by NEM concentrations equal to or higher than 0.5 mM. Under our experimental conditions, PCMBS (1 mM) exerted a strong inhibition on [¹⁴C]sucrose uptake but did not inhibit proton extrusion and ⁸⁶Rb uptake. The sensitivity of phloem loading to PCMBS is thought to be a consequence of sugar-carrier blockage and not of inhibition of the proton pump.Abbreviations CCCP carbonylcyanide-m-chlorophenylhydrazone - DES diethylstilbestrol - DCCD dicyclohexylcarbodiimide - FC Fusicoccin - NEM N-ethylmaleimide - PCMBS p-chloromercuribenzenesulfonic acid     

Monocyte aggregation and superoxide anion release in response to formyl-methionyl-leucyl-phenylalanine (FMLP) and platelet-activating factor (PAF)

Like the PMN, human peripheral blood monocytes were capable of aggregating in response to FMLP and PAF. Monocyte aggregation was dependent on glycolysis and the presence of divalent cations. Unlike the PMN, monocyte aggregation in response to FMLP was not accompanied by degranulation, nor was it potentiated by cytochalasin B. Furthermore, cytochalasin B and its cogenitor, dihydrocytochalasin B, inhibited aggregation in response to PAF. PAF and FMLP appeared to react with the monocyte at separate receptors because sequential challenge of the monocyte with the same agents failed to elicit further aggregation, whereas rechallenge with the alternative agent induced further aggregation. Because the monocyte will aggregate to chemotactic agents in vitro, it is likely that the cell will be affected by these agents in vivo, which could lead to leukoembolization of circulating monocytes.     

Sphingosine 1-phosphate promotes antigen processing and presentation to CD4+ T cells in Mycobacterium tuberculosis-infected monocytes

It was previously shown that cells die with increased cytosolic ATP after stimulation with apoptotic inducers including staurosporine (STS). To identify the source of apoptotic ATP elevation, we monitored, in real time, the cytosolic ATP level in luciferase-expressing HeLa cells. A mitochondrial uncoupler or a respiration chain inhibitor was found to decrease cytosolic ATP by about 50%. However, even when mitochondrial ATP synthesis was suppressed, STS induced a profound elevation of intracellular ATP. In contrast, the STS-induced ATP increase was prevented by any of three inhibitors of the glycolytic pathway: 2-deoxyglucose, iodoacetamide, and NaF. The STS effect strongly depended on intracellular calcium and was mimicked by a calcium ionophore. We conclude that Ca(2+)-dependent activation of anaerobic glycolysis, but not aerobic mitochondrial oxidative phosphorylation, is responsible for the STS-induced elevation of ATP in apoptotic HeLa cells.     

Inhibition of receptor-mediated endocytosis immunoglobulin G by enterocytes isolated from the neonatal rat jejunum

The effect of inhibitors of respiration (NaN3 and DNP), glycolysis (2DG, IAA and NaF) and the microtubular-microfilament system (colchicine and cytochalasin B) on the uptake of rat immunoglobulin G (IgG) by enterocytes isolated from the neonatal rat gut has been assessed. After a 1 hour incubation, NaN3, and DNP had significantly reduced IgG uptake by between 32% and 35% of the control, IAA and 2DG were less effective and NaF, colchicine and cytochalasin B had no effect at all. The findings show that IgG is internalised by isolated enterocytes in vitro and that this internalisation is under metabolic control, that inhibitors of respiration are more effective in blocking uptake than inhibitors of glycolysis.