Plasma membrane adenosine triphosphatases in rat peritoneal mast cells and macrophages--the relation of the mast cell enzyme to histamine release

Cellular Distribution and Functions of P2 Receptor Subtypes in Different Systems

This review is aimed at providing readers with a comprehensive reference article about the distribution and function of P2 receptors in all the organs, tissues, and cells in the body. Each section provides an account of the early history of purinergic signaling in the organ?cell up to 1994, then summarizes subsequent evidence for the presence of P2X and P2Y receptor subtype mRNA and proteins as well as functional data, all fully referenced. A section is included describing the plasticity of expression of P2 receptors during development and aging as well as in various pathophysiological conditions. Finally, there is some discussion of possible future developments in the purinergic signaling field.

The effects of some possible inhibitors of ectonucleotidases on the breakdown and pharmacological effects of ATP in the guinea-pig urinary bladder

1. The effects of some possible inhibitors of ectonucleotidases on the breakdown of extracellular ATP by strips of guinea-pig urinary bladder were investigated. 2. Suramin and ethacrynic acid (10 mM) both inhibited ATP breakdown significantly, and difluorodinitrobenzene (10 mM) inhibited it slightly whereas N-ethylmaleimide, adenosine 5'-(gamma-thiotriphosphate) (ATP-gamma-S) and reactive blue-2 (10 mM) were without effect. 3. The inhibitory effects of suramin on ATP breakdown were non-competitive. 4. Ethacrynic acid (1 mM) irreversibly inhibited contractions of the guinea-pig bladder induced by ATP, substance P, histamine, non-adrenergic, non-cholinergic nerve stimulation or KCl, whereas suramin (100 microM) had no inhibitory effect. 5. The results suggest that suramin might provide a starting point for the design of selective inhibitors of ectonucleotidases.

Changes in some histochemically demonstrable enzymes in macrophages exposed to quartz dust in vitro

Cytochemical studies were carried out on rat alveolar and peritoneal macrophage cultures following exposure to quartz and corundum dusts. Quartz increased the number of ATPase positive cells and brought about an enhancement in the peroxidase and diffusion of the acid phosphatase activity of the exposed cells. In unexposed cell cultures, acid phosphatase activity was higher in alveolar than in peritoneal macrophages and was dependent upon the duration of incubation. Corundum produced no significant effect on the enzyme activity. Quartz treatment did not alter esterase activity whereas corundum exposed cultures showed a decline. A significant increase in mitochondrial succinic dehydrogenase activity was observed in peritoneal macrophages after quartz treatment. The results demonstrate alteration in the marker enzymes of plasma membranes, mitochondria and lysosomes during phagocytosis of quartz dust as the key event of dust cell interaction in vitro.

No direct involvement of plasma membrane divalent cation-activated adenosine triphosphatase in histamine release from rat mast cells

Showdomycin, a very slowly penetrating SH reagent, hardly affected the histamine release induced by any of secretagogues tested, suggesting no exposure of sulfhydryl groups involved in the granule secretion process on the cell surface. N-ethylmaleimide(NEM), a considerably penetrating SH reagent, almost completely inhibited histamine release induced by secretagogues such as compound 48/80, polymyxin B, concanavalin A or digitonin at 100 microM and by A23187 at 500 microM. However, (Ca2+-Mg2+)-ATPase activity was hardly inhibited by NEM modification at 500 microM. These findings suggest that plasma membrane divalent cation-activated ATPase is not involved directly in the granule secretion process of mast cells.

Role of a Ca2+-Mg2+ ATPase on the mast cell surface in calcium transport and histamine secretion

We have previously reported the presence of an ATPase, stimulated by calcium and magnesium, on the outer surface of the rat peritoneal mast cell. Experiments in which the enzyme activity was enhanced or inhibited showed a relationship to histamine secretion. Enhanced enzyme activity with increasing concentrations of the substrate (ATP) was associated with a potentiation of histamine release, and a pronounced inhibition of the enzyme caused an inhibition of the release. In the present work we have studied the influx and efflux of calcium in mast cells in relation to the activity of the Ca2+-Mg2+ ATPase on the mast cell membrane. The enzyme activity is shown to be related to calcium influx and has no effect on calcium efflux. Stimulation of the enzyme with ATP is associated with increased calcium influx into the mast cell, and inhibition of the enzyme with AMP causes inhibition of the calcium uptake. In both cases calcium efflux is unaffected. The function of the enzyme is thus different from the calcium efflux enzyme on the cytoplasmic surface, described in other cells. In addition, the Ca2+-Mg2+ ATPase on the mast cell surface is neither stimulated by calmodulin nor inhibited by the calmodulin antagonists, trifluoperazine and W-7. In mast cells the low cytosolic calcium concentration seems to be maintained by Na+-Ca2+ countertransport. Phosphorylation of the Ca2+-Mg2+ ATPase on the mast cell is likely to be associated with Ca2+ release at the cytoplasmic surface of the plasma membrane. It is thus possible that ATP hydrolysis in the membrane stimulates the contraction of microfilaments in the membrane and the cytoskeleton, and promotes the migration of the granules to the plasma membrane.

Effects of dimethylsulfoxide (DMSO), nocodazole, and taxol on mast cell histamine secretion

Nocodazole depolymerized microtubules and increased the number of microfilaments, and dimethylsulfoxide increased the number of microfilaments. Both drugs inhibited compound 48/80-induced histamine release from rat mast cells. Taxol, which increased the number of microtubules, had no effect on histamine release. These observations support the view that microtubules may not be directly involved in secretion, but apparently an increased number of microfilaments is associated with a decreased capacity of the mast cells for histamine release. We suggest that microfilaments have to be depolymerized or rearranged before secretion can take place.

Comparison of the rat microsomal Mg-ATPase of various tissues

The microsomal Mg-ATPase from various rat tissues was compared. After fractionating the microsomal vesicles by sucrose gradient centrifugation, the highest specific activity of the Mg-ATPase was found in the low-density vesicles which contained plasma membrane. A large fraction (25-90%) of the microsomal Ca-independent Mg-ATPase found in each tissue had the following properties: (1) the Km for ATP was 0.2 mM; (2) the rate of ATP hydrolysis by the Mg-ATPase was nonlinear due to an ATP-stimulated inactivation of the enzyme; (3) wheat germ agglutinin, concanavalin A, glutaraldehyde, and antiserum prevented inactivation induced by ATP or AdoPP[NH]P; (4) detergents at relatively low detergent:protein ratios increased the rate of inactivation with little change in the initial rate of ATP hydrolysis; (5) the Mg-ATPase was inactivated by irradiation in the presence of 8-azido ATP. (6) in addition to ATP, the Mg-ATPase was able to hydrolyze CTP, GTP, UTP, ITP, and GTP but was unable to hydrolyze any of the 10 nonnucleotide phosphocompounds which were tested; (7) the bivalent cation requirement of the Mg-ATPase could be provided by Mg2+, Ca2+, Mn2+, Zn2+, or Co2+ but the enzyme was inactive in the presence of Cu2+, Sr2+, Ba2+, or Be2+; (8) the Mg-ATPase activity was not altered by ionophores or inhibitors of the Na,K-ATPase, the Ca,Mg-ATPase or the mitochondrial F1ATPase. These data suggest that a major portion of the microsomal, basal Mg-ATPase activity is due to one unique enzyme found in most if not all tissues.

Presence of a high-affinity Ca2+- and Mg2+-dependent ATPase in rat peritoneal mast-cell membranes

Purified perigranular and plasma membranes isolated from rat peritoneal mast cells were examined for Ca2+- and Mg2+-dependent ATPase activity. Isolated perigranular membranes contained only a low-affinity Ca2+- or Mg2+-dependent ATPase (Km greater than 0.5 mM). The plasma membranes contained both a low-affinity Ca2+- or Mg2+-dependent ATPase (Km = 0.4 mM, Vmax. = 20 nmol of Pi/min per mg), as well as a high-affinity Ca2+- and Mg2+-dependent ATPase (Km = 0.2 microM, Vmax. = 6 nmol of Pi/min per mg).

Alteration of lymphocyte function by quinones through a sulfhydryl-dependent disruption of microtubule assembly

The cytoskeleton plays a pivotal role in lectin-induced lymphocyte blastogenesis. Microtubule disrupting agents, many of which are sulfhydryl (SH) reagents, interfere with cytoskeletal-dependent cell functions including lymphocyte blastogenesis and agglutination. For example, hydroquinone (HQ) and N-ethylmaleimide (NEM) inhibit lectin-stimulated lymphocyte blastogenesis and agglutination at concentrations (10(-5)M) that do not reduce cell viability or ATP production. Indicative of the SH-specificity of these effects, only L-cysteine protects against HQ or NEM inhibition of blastogenesis and agglutination. Other compounds, including L-serine, DL-lysine and imidazole, have no protective effect. These and other findings previously reported suggest a selective interaction of HQ, or its oxidation product, p-benzoquinone (p-BQ) with SH groups critical to early G1 events associated with lymphocyte activation. These compounds show similar SH specificity in inhibiting microtubule assembly in vitro. The subcellular target specificity (cytoskeleton) exhibited by these compounds was compared to that of Adriamycin (ADR), a complex polycyclic quinone with known immunotoxic activity. ADR inhibited microtubule assembly in vitro and inhibited lymphocyte blastogenesis, however, these effects were not correlated with a loss of agglutination nor was toxicity protected against by the addition of SH compounds. The combination of cell culture methods together with application of techniques to measure microtubule assembly in vitro provides an effective means to discriminate between agents that selectively interfere with cytoskeletal-dependent function and those producing non-specific effects associated with cell death, such as decreased energy production or increased membrane permeability.

Inhibition of some polymorphonuclear leukocyte functions by ethacrynic acid

Ethacrynic acid (10(-4) M) inhibits exocytosis, phagocytosis and superoxide release in rabbit polymorphonuclear leukocytes (PMN's). Dihydroethacrynic acid is a much weaker inhibitor of these PMN functions. Though ethacrynic acid inhibits ATPase activity in the PMN, this occur at much higher concentrations than required for inhibition of exocytosis and superoxide release, thus a causal relationship seems unlikely. The same applies to inhibition of ATP generation by ethacrynic acid: the concentration required to decrease ATP level in PMN's is much higher than required for the inhibitory effect on exocytosis. Inhibition of exocytosis by ethacrynic acid can be prevented by dithiothreitol. It is concluded that vulnerable sulfhydryl groups are involved in the inhibition by ethacrynic acid.

Electron microscopic study of the regeneration in vitro of rat peritoneal mast cells after histamine secretion

Regeneration of rat mast cells was studied by TEM from 10 s to 48 h after secretion of histamine induced by compound 48/80. During the first 2 h, small intracellular cavities, formed during compound exocytosis and containing non-membrane-bound remnants of the granules, tended to coalesce, and after 2 h of incubation regeneration started. After 6 h, all the cavities had fused into one large central cavity which contained the remnants of the granules and remained open to the exterior during the entire period. The plasma membrane microfolds which disappeared just after secretion were reformed during regeneration. They were apparently involved in endocytotic-like activity and coated vesicles also appeared beneath the plasmalemma (membrane recycling?). The fate of the granule remnants in the cavity is unknown, as regeneration was not completed after 48 h which is the longest survival time obtained so far in ultrastructural studies of mast cell regeneration in vitro.

Subcellular localization and properties of adenosine triphosphatase in human polymorphonuclear leucocytes

Magnesium-dependent adenosine triphosphatase (Mg2+-ATPase) activities wee studied in human neutrophilic polymorphonuclear leucocytes. Kinetic studies on whole leucocyte homogenates produced curvilinear kinetics suggesting the presence of at least two forms of Mg2+-ATPase. Neutrophils were homogenized in isotonic sucrose and, after low-speed centrifugation, the supernatant was subjected to analytical subcellular fractionation. Gradient fractions were assayed for Mg2+-ATPase and for principal organelle marker enzymes. Mg2+-ATPase was distributed between the plasma membrane, mitochondrial and cytosol fractions. Kinetic and inhibitor studies on Mg2+-ATPase from each localization indicated the presence of three forms of the enzyme. The plasma membrane and mitochondrial activities had a Km value of 0.2 mmol/l for ATP, whilst the Km for the cytosolic enzyme was 1.8 mmol/l. Inhibitor studies showed further differences between the three enzymes. Neutrophils were isolated from control subjects, patients with chronic granulocytic leukaemia and patients in the third trimester of pregnancy. The specific activities (mUnits/mg protein) of Mg2+-ATPase, in contrast to those of alkaline phosphatase, were similar in all three patient groups. This result, together with the fractionation experiments and inhibitor studies, strongly suggest that the ATPase is not attributable to neutrophil alkaline phosphatase.

Role of adenylate cyclase in immunologic release of mediators from rat mast cells: agonist and antagonist effects of purine- and ribose-modified adenosine analogs

The initial monophasic rise in cyclic AMP beginning 5-15 sec after bridging of rat mast cell IgE-Fc receptors precedes the secretion of granule constituents, thereby implying a causal relationship. Direct evidence for a relationship between IgE-dependent transmembrane activation of adenylate cyclase and granule secretion was provided by the capacity of purine-modified (R site active) and ribose-modified (P site active) adenosine analogs, respectively, to augment and suppress mediator release while simultaneously increasing and decreasing the activity of adenylate cyclase. R site stimulation alone does not cause granule secretion but augments the rate and magnitude of IgE-Fc receptor-induced secretion, reflecting the coupled relationship of such receptors. Inhibition of adenylate cyclase at the P site attenuates the rise in cellular cyclic AMP and suppresses IgE-dependent mediator release in a parallel and superimposable dose-response fashion. Further, the relationship between the attenuation in the rise in cyclic AMP and the diminution in immunologic mediator release is linear with the regression line passing through the origin, indicating a direct relationship between the IgE-dependent activation of adenylate cyclase and preformed mediator release. Although not the only events in coupled mast cell activation--secretion, there is a sequential relationship among perturbation of IgE-Fc receptors, transmembrane activation of adenylate cyclase, elevation of cytoplasmic levels of cyclic AMP, activation of cyclic AMP-dependent protein kinase, and secretion of mast cell granules.

The role of plasma membrane Ca++-Mg++ activated adenosine triphosphatase of rat mast cells on histamine release

The role of a Ca++-MG++ activated ATPase, demonstrated on the outer surface of rat peritoneal mast cells, on histamine release induced by antigen (anaphylactic reaction), compound 48/80 and ionophore A23187 has been studied. A high level of the enzyme activity is retained at the optimal pH for histamine release induced by the three releasing agents. The effect of fourteen inhibitors of ATPase has been studied, viz. quinidine, fluoride, platinum salt, suramin, ethacrynic acid, ethyl alcohol, N-ethylmaleimide, Mn++, Ni++, ADP, AMP and the flavones: kaempferol, quercetin, morin. All the inhibitors, which caused varying degrees of inhibition of ATPase, also inhibited histamine release. The inhibition of the enzyme was competitive with ADP, AMP, ethacrynic acid, suramin and morin and non-competitive with the others. The degree of inhibition of ATPase and of histamine release tended to be similar with six inhibitors. With the others the extent of the inhibition of the release and of the enzyme varied. But a marked inhibition of the enzyme was always associated with a pronounced inhibition of histamine release. ATP in lower concentrations (10-20 microM) has been shown to potentiate histamine release induced by all the three releasers, possibly through its utilization by plasma membrane ATPase. The observations agree with the hypothesis that plasma membrane ATPase participates in the histamine release process.

Metabolism of adenine nucleotides by ectoenzymes of vascular endothelial and smooth-muscle cells in culture

1. Pig aortic endothelial and smooth-muscle cells in culture rapidly catabolize exogenous ATP, ADP or AMP. 2. In both cell types catabolism is due to Mg2+-stimulated ectoenzymes. 3. Inhibition and substrate-specificity studies suggest that both cell types possess three distinct ectonucleotidases, namely nucleoside triphosphatase (EC 3.6.1.15), nucleoside diphosphatase (EC 3.6.1.6) and 5'-nucleotidase (EC 3.1.3.5), as well as nucleoside diphosphate kinase (EC 2.7.4.6). 4. These ectonucleotidase systems could be of importance in the regulation of neurotransmission, blood platelet function and vasodilation.

Effects of sulfhydryl reagents on phagocytosis and exocytosis in rabbit polymorphonuclear leukocytes

The effect of sulfhydryl reagents on phagocytosis and concomitant enzyme release and on ionophore A 23187 + Ca2+-induced exocytosis in rabbit polymorphonuclear leukocytes (PMN's) was studied. Membrane-penetrating sulfhydryl reagents such as cytochalasin A and N-naphthylmaleimide in micromolar concentrations inhibit both phagocytosis and exocytosis. Poorly penetrating reagents such as p-chloromercuribenzene sulfonate (pCMBS) and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), inhibit only in high concentrations (pCMBS), or they are ineffective as inhibitors (DTNB). Inhibition by pCMBS is not reversed by glutathione or dithiothreitol; this suggests that some pCMBS probably enters the cell. Specific intracellular sulfhydryl compounds appear to be essential in the cellular apparatus involved in phagocytosis and exocytosis; various possibilities are considered. A concentration of N-naphthylmaleimide which completely inhibits phagocytosis and exocytosis leaves cellular ATPase activity intact.