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C P Wheeler-Jones

Publications and source records attributed to C P Wheeler-Jones.

At least 19 recordsLinked to original sources
PubMed2001

sPLA(2) cooperates with cPLA(2)alpha to regulate prostacyclin synthesis in human endothelial cells.

The first step in prostacyclin (PGI(2)) synthesis involves the generation of arachidonic acid (AA) from membrane phospholipids mediated by the 85 kDa cytosolic phospholipase A(2) (cPLA(2)alpha). The current study examined the effects of secretory PLA(2)s (sPLA(2)s) on PGI(2) production by human umbilical vein endothelial cells (HUVEC). We demonstrate that exposure of HUVEC to sPLA(2) dose- and time-dependently enhances AA release and PGI(2) generation. sPLA(2)-stimulated AA mobilisation was blocked by AACOCF(3), an inhibitor of cPLA(2)alpha, suggesting cross-talk between the two classes of PLA(2). sPLA(2) induced the phosphorylation of cPLA(2)alpha and enhanced the phosphorylation states of p42/44(mapk), p38(mapk), and JNK, concomitant with elevated AA and PGI(2) release. The MEK inhibitor PD98059 attenuated sPLA(2)-stimulated cPLA(2)alpha phosphorylation and PGI(2) release. These data show that sPLA(2) cooperates with cPLA(2)alpha in a MAPK-dependent manner to regulate PGI(2) generation and suggests that cross-talk between sPLA(2) and cPLA(2)alpha is a physiologically important mechanism for enhancing prostanoid production in endothelial cells.

Arachidonic Acid↗
PubMed2001

Agonist-specific cross talk between ERKs and p38(mapk) regulates PGI(2) synthesis in endothelium.

We have examined the mechanisms regulating prostacyclin (PGI(2)) synthesis after acute exposure of human umbilical vein endothelial cells (HUVEC) to interleukin-1 alpha (IL-1 alpha). IL-1 alpha evoked an early (30 min) release of PGI(2) and [(3)H]arachidonate that was blocked by the cytosolic phospholipase A(2)alpha (cPLA(2)alpha) inhibitor arachidonyl trifluoromethyl ketone. IL-1 alpha-mediated activation of extracellular signal-regulated kinase 1/2 (ERK1/2; p42/p44(mapk)) coincided temporally with phosphorylation of cPLA(2)alpha and with the onset of PGI(2) synthesis. The mitogen-activated protein kinase (MAPK) kinase (MEK) inhibitors, PD-98059 and U-0126, blocked IL-1 alpha-induced ERK activation and partially attenuated cPLA(2)alpha phosphorylation and PGI(2) release, suggesting that ERK-dependent and -independent pathways regulate cPLA(2)alpha phosphorylation. SB-203580 treatment enhanced IL-1 alpha-induced MEK, p42/44(mapk), and cPLA(2)alpha phosphorylation but reduced thrombin-stimulated MEK and p42/44(mapk) activation. IL-1 alpha, but not thrombin, activated Raf-1 as assessed by immune-complex kinase assay, as did SB-203580 alone. These results show that IL-1 alpha causes an acute upregulation of PGI(2) generation in HUVEC, establish a role for the MEK/ERK/cPLA(2)alpha pathway in this early release, and provide evidence for an agonist-specific cross talk between p38(mapk) and p42/44(mapk) that may reflect receptor-specific differences in the signaling elements proximal to MAPK activation.

Arachidonic Acid↗
PubMed2001

Mechanical strain and estrogen activate estrogen receptor alpha in bone cells.

Bone cells' early responses to estrogen and mechanical strain were investigated in the ROS 17/2.8 cell line. Immunoblotting with antiphosphorylated estrogen receptor a (ER-alpha) antibody showed that when these cells were exposed for 10 minutes to estrogen (10(-8) M) or a single period of cyclic dynamic strain (peak 3400 microepsilon, 1 Hz, 600 cycles), there was an increase in the intensity of a 66-kDa band, indicating phosphorylation of ser122 in the amino terminus of ER-alpha. Increased phosphorylation was detected within 5 minutes of exposure to estrogen and 5 minutes after the end of the period of strain. Estrogen and strain also activated the mitogen-activated protein kinase (MAPK) family member extracellular regulated kinase-1 (ERK-1). Increases in ERK activation coincided with increased ER-alpha phosphorylation. Activation of ERK-1 and the phosphorylation of ER-alpha, by both estrogen and strain, were prevented by the MAP kinase kinase (MEK) inhibitor U0126 and the protein kinase A (PKA) inhibitor (PKI). These data support previous suggestions that resident bone cells' early responses to strain and estrogen share a common pathway, which involves ER-alpha. This pathway also appears to involve PKA and ERK-mediated phosphorylation of ser122 within the amino terminus of ER-alpha. Reduced availability of this pathway when estrogen levels are reduced could explain diminished effectiveness of mechanically related control of bone architecture after the menopause.

Bone and Bones↗
PubMed2000

Arachidonic acid for loading induced prostacyclin and prostaglandin E(2) release from osteoblasts and osteocytes is derived from the activities of different forms of phospholipase A(2).

Mechanical loading of bone stimulates resident bone cells to produce prostacyclin (PGI(2)) and prostaglandin (PG)E(2) by a mechanism that can be differentially regulated by ion channel blockers. We have investigated differences in the loading-related PG production mechanisms in rat ulnae explants loaded ex vivo. Loading and aluminium fluoride (AlF(3), a nonselective activator of G-proteins) both increased PGI(2) and PGE(2) release into culture medium. Pertussis toxin (PTX) blocked loading-related release of PGE(2), but not PGI(2), while isotetrandrine, an inhibitor of G-protein-mediated activation of phospholipase (PL)A(2), abolished the loading-related release of both PGs. This suggests both PTX-sensitive and -insensitive G-protein-dependent, PLA(2)-mediated mechanisms for loading-related PG production. Blockade of secretory (s)PLA(2) activity prevented loading-related release of PGE(2) and PGI(2), whereas inhibition of cytosolic (c)PLA(2) activity blocked loading-related release of PGE(2) alone. cPLA(2) was localized immuno-cytochemically to osteoblasts, but not to osteocytes. sPLA(2) was localized to osteocytes and osteoblasts. Exogenous type-IA sPLA(2) and type-IB sPLA(2) stimulated significant increases in PGE(2) and PGI(2) release. PTX reduced the release of both PGs stimulated by type IA PLA(2), but not type IB. Furthermore, inhibition of protein kinase C (PKC) activity blocked loading-related release of PGE(2), but not that of PGI(2). These data suggest that loading-related release of PGI(2) and PGE(2) utilizes arachidonic acid derived from the activity of different PLA(2)s. In osteocytes and osteoblasts, arachidonic acid for PGI(2) synthesis is liberated by PTX-insensitive G-protein-dependent sPLA(2) alone. In osteoblasts, arachidonic acid for PGE(2) synthesis is released by PTX-sensitive, G-protein-dependent, cPLA(2)-mediated activity, which also requires upstream sPLA(2) and PKC activities.

Alkaloids↗
PubMed2000

Acute effects of interferon on estrogen receptor function do not involve the extracellular signal-regulated kinases p42mapk and p44mapk.

Exposure to type I interferons (IFN) increased estrogen receptor (ER) ligand binding and induced protein kinase C (PKC) translocation within 30 min but had no effect on net incorporation of [32P] into ER in Madin Darby bovine kidney (MDBK) cells. Ligand binding was also increased within 30 min by phorbol ester and the protein phosphatase inhibitor okadaic acid. Mitogen-activated protein (MAP) kinase phosphorylation was initially inhibited between 2 and 30 min and subsequently activated between 30 and 60 min after treatment with IFN. The activatory response was blocked by the PKC inhibitor Ro 31-8220. Following transient transfection with an ERE-CAT reporter construct, IFN increased CAT expression after 6 h but decreased ER ligand binding, transcriptional activity and phosphorylation after 48 h, probably as a result of decreased ER concentrations. The results rule out rapid activation of ER ligand binding through phosphorylation at Ser118 by MAP kinase because (1) the increase in ligand binding preceded activation of MAP kinase, and (2) IFN had no short-term effect on [32P]incorporation or ER transcriptional activity. The rapid effect of IFN on ER ligand binding is postulated to reflect phosphorylation of the receptor at Tyr537 by p56lck, a member of the Src family of PKC-activated tyrosine kinases.

Animals↗
PubMed1999

Transmembrane signalling mechanisms regulating expression of cationic amino acid transporters and inducible nitric oxide synthase in rat vascular smooth muscle cells.

The signalling mechanisms involved in the induction of nitric oxide synthase and l-arginine transport were investigated in bacterial lipopolysaccharide (LPS)- and interferon-gamma (IFN-gamma)-stimulated rat cultured aortic smooth muscle cells (RASMCs). The expression profile of transcripts for cationic amino acid transporters (CATs) and their regulation by LPS and IFN-gamma were also examined. Control RASMCs expressed mRNA for CAT-1, CAT-2A and CAT-2B. Levels of all three transcripts were significantly elevated in activated cells. Stimulated CAT mRNA expression and l-arginine transport occurred independently of protein kinase C (PKC), protein tyrosine kinase (PTK) and p44/42 mitogen-activated kinases (MAPKs), but were inhibited by the p38 MAPK inhibitor SB203580, which at 3 microM caused maximum inhibition of both responses. Induction of NO synthesis was independent of p44/42 MAPK activation and only marginally dependent on PKC, but was attenuated markedly by the PTK inhibitors genistein and herbimycin A. SB203580 differentially regulated inducible NO synthase expression and NO production, potentiating both processes at low micromolar concentrations and inhibiting at concentrations of >/=1 microM. In conclusion, our results suggest that RASMCs constitutively express transcripts for CAT-1, CAT-2A and CAT-2B, and that expression of these transcripts is significantly enhanced by LPS and IFN-gamma. Moreover, stimulation of l-arginine transport and induction of NO synthesis by LPS and IFN-gamma appear to be under critical regulation by the p38 MAPK, since both processes were significantly modified by SB203580 at concentrations so far shown to have no effect on other signalling pathways. Thus, in RASMCs, the p38 MAPK cascade represents an important signalling mechanism, regulating both enhanced l-arginine transport and induced NO synthesis.

Amino Acid Transport Systems, Basic↗
PubMed1998

Activation of p42mapk in human umbilical vein endothelial cells by interleukin-1 alpha and tumor necrosis factor-alpha.

Work from this and other laboratories has identified a role for protein tyrosine kinases in interleukin-1 alpha (IL-1 alpha)- and tumor necrosis factor-alpha (TNF-alpha)-induced responses in endothelial cells. In this study, we show that activation of human umbilical vein endothelial cells (HUVEC) by IL-1 alpha leads to increased tyrosine phosphorylation of several proteins including one with a molecular mass of approximately 42 kDa. This protein was identified as p42mapk by Western blot analysis. Tyrosine phosphorylation and catalytic activation of p42mapk by IL-1 alpha was transient, reaching maximal levels after 30 min and returning to basal levels by 120-300 min. Activation of p42mapk in HUVEC was also observed in response to TNF-alpha or to the protein kinase C (PKC)-activating phorbol ester phorbol 12-myristate 13-acetate (PMA). Pretreatment of HUVEC with IL-1 alpha or TNF-alpha prevented reactivation of p42mapk by either cytokine but did not affect subsequent activation in response to PMA. Activation of p42mapk by PMA was significantly reduced by the PKC inhibitor Ro-31-8220 and completely inhibited by the protein tyrosine kinase inhibitor genistein. Genistein, but not Ro-31-8220, attenuated IL-1 alpha- and TNF-alpha-induced p42mapk activation. Taken together, the results of this study demonstrate 1) that p42mapk is transiently activated in HUVEC by IL-1 alpha and TNF-alpha, 2) that this activation is PKC independent, and 3) that a genistein-inhibitable tyrosine kinase may be an upstream regulator of cytokine-induced p42mapk activation in human endothelium.

Catalysis↗
PubMed1996

Inhibition of MAP kinase kinase (MEK) blocks endothelial PGI2 release but has no effect on von Willebrand factor secretion or E-selectin expression.

We have examined the potential role of MAP kinase in the regulation of endothelial cell PG12 synthesis, vWF secretion and E-selectin expression using the specific MEK inhibitor PD98059. PD98059 dose-dependently attenuated the tyrosine phosphorylation and activation of p42 mapk in response to thrombin or inflammatory cytokines. Inhibition of thrombin-induced p42 mapk activation was paralleled by an inhibitory effect of PD98059 on thrombin-driven PG12 generation but not on vWF secretion or IL-1 alpha/TNF alpha-induced E-selectin expression. These results provide evidence for a key role for p42 mapk in the acute regulation of PG12 synthesis in human endothelial cells and suggest that activation of the MAP kinase cascade is not obligatory for cytokine-stimulated E-selectin expression.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1996

Protein tyrosine kinases regulate agonist-stimulated prostacyclin release but not von Willebrand factor secretion from human umbilical vein endothelial cells.

The rapid synthesis and release of prostacyclin (PGI2) and the exocytotic secretion of von Willebrand Factor (vWF) elicited by activation of G-protein-coupled receptors on endothelium occur via signaling mechanisms which are incompletely defined. Activation of protein tyrosine kinases (PTKs) and modulation of the tyrosine-phosphorylation state of endogenous proteins have been implicated in several cellular processes including arachidonate release and exocytosis. In the present study we have examined the regulatory role of PTKs in agonist-stimulated release of PGI2 and vWF from human umbilical vein endothelial cells (HUVECs) using two chemically and mechanistically dissimilar PTK inhibitors (genistein and ST271). Genistein, but not the less active analogue daidzein, dose-dependently attenuated PGI2 release in response to thrombin and histamine (IC50 approx. 20 microM), and to the thrombin-receptor-activating peptide. A more potent inhibition of thrombin- and histamine-induced PGI2 synthesis was observed in cells exposed to ST271. In contrast, neither genistein nor ST271 modulated agonist-drive vWF secretion. At concentrations that abolished PGI2 release, genistein blocked thrombin- or histamine-evoked tyrosine phosphorylation of a 42 kDa protein. Ca2+ ionophore-induced PGI2 generation, but not vWF secretion, was also inhibited by both genistein and ST271, suggesting that these agents modulate PGI2 synthesis by acting at, or distal to, agonist-induced changes in intracellular CA2+ ([Ca2+]i). In fura-2-loaded HUVECs genistein partially reduced the histamine-induced peak [Ca2+]i but had no effect on the thrombin response. Ca(2+)-induced PGI2 release from electrically permeabilized HUVECs was abolished in the presence of ST271 or genistein, but not diadzein. The generation of PGI2 in response to exogenous arachidonic acid was not modulated by genistein or ST271, suggesting that PTK inhibitors do not directly inhibit cyclo-oxygenase activity. Taken together, these results suggest that PTKs regulate PGI2 synthesis and release in HUVECs by modulating, directly or indirectly, a CA(2+)-sensitive step upstream of cyclo-oxygenase.

Calcium↗
PubMed1996

Identification of 14-3-3 proteins in human platelets: effects of synthetic peptides on protein kinase C activation.

The 14-3-3 proteins inhibit protein kinase C (PKC) activity in vitro and contain conserved sequences that resemble the pseudosubstrate domain of PKC and the C-terminus of the annexins. In the present study we have identified the isoforms of 14-3-3 in human platelets and used synthetic peptides derived from the regions with similarity to PKC and annexins to examine the potential role of 14-3-3 in regulating platelet activity. Immunoblotting studies with isoform-specific antisera raised against the acetylated peptides corresponding to the N-termini of 14-3-3 showed that these cells express high levels of the beta, gamma and zeta 14-3-3 isoforms. In addition, low levels of the epsilon and eta 14-3-3 isoforms were detected. In washed, saponin-permeabilized platelets incubated with [gamma-32P]ATP, thrombin- and phorbol 12-myristate 13-acetate (PMA)-induced phosphorylation of several proteins (66, 45, and 20kDa) was inhibited by preincubation with AS peptide (KNVVGARRSSWRVISSIEQK) based on the pseudosubstrate-like region of the 14-3-3 family. A control peptide of similar size had no effect on PKC-mediated phosphorylation. PMA caused a rapid translocation of PKC activity from the cytosol to the particulate fraction of saponin-permeabilized platelets that was unaffected by either the AS peptide or a peptide derived from the annexin-like 14-3-3 domain (MKGDYYRYLAEVATGDD). These results suggest that isoforms of the 14-3-3 family may play an important physiological role as inhibitors of PKC activity in human platelets but are unlikely to be involved in controlling association of PKC with the membrane.

14-3-3 Proteins↗
PubMed1996

The mitogen-activated protein kinase pathway in rat islets of Langerhans: studies on the regulation of insulin secretion.

The expression of mitogen-activated protein kinases (MAPKs) and MAPK kinases (MEKs) in rat islets of Langerhans and the involvement of MAPKs in regulated insulin secretion were examined. Two major isoforms of both MEK (45 and 46 kDa) and MAPK (42 and 44 kDa) were detected in rat islets and shown to be localized to insulin-secreting beta cells by detection of their expression in the beta cell line MIN6. The tyrosine phosphatase inhibitor sodium pervanadate, and, to a lesser extent, the serine/threonine phosphatase inhibitor okadaic acid, stimulated MAPK phosphorylation, as assessed by a shift in its electrophoretic mobility and by increased phosphotyrosine immunoreactivity of immunoprecipitated MAPK. The increase in MAPK phosphorylation stimulated by sodium pervanadate was not coupled to an increase in MAPK activity, but okadaic acid, either alone or in the presence of sodium pervanadate, caused an increase in myelin basic protein phosphorylation by MAPK. Neither okadaic acid nor sodium pervanadate, either individually or combined, stimulated insulin secretion. 4 beta-phorbol myristate acetate stimulated an increase in phosphorylation of the 42 kDa isoform of MAPK (erk2) in human umbilical vein endothelial cells, but neither it nor glucose affected either the phosphorylation state of islet erk2 or the activities of immunoprecipitated islet MAPKs. These results provide evidence for the presence of a regulated MAPK pathway in adult rat islets, but our data suggest that MAPK activation alone is not a sufficient stimulus for insulin secretion.

Animals↗
PubMed1996

Inhibition of inducible nitric oxide synthase expression by novel nonsteroidal anti-inflammatory derivatives with gastrointestinal-sparing properties.

1. The effects of novel nitric oxide-releasing nonsteroidal anti-inflammatory compounds (NO-NSAIDs) on induction of nitric oxide (NO) synthase by bacterial lipopolysaccharide (LPS) were examined in a murine cultured macrophage cell line, J774. 2. LPS-induced nitrite production was markedly attenuated by the nitroxybutylester derivatives of flurbiprofen (FNBE), aspirin, ketoprofen, naproxen, diclofenac and ketorolac, with each compound reducing accumulated nitrite levels by > 40% at the maximum concentrations (100 micrograms ml-1) used. 3. Further examination revealed that nitrite production was inhibited in a concentration-dependent (1-100 micrograms ml-1) manner by FNBE which at 100 micrograms ml-1 decreased LPS-stimulated levels by 63.3 +/- 8.6% (n = 7). The parent compound flurbiprofen was relatively ineffective over the same concentration-range, inhibiting nitrite accumulation by 24 +/- 0.9% (n = 3) at the maximum concentration used (100 micrograms ml-1). 4. FNBE reduced LPS-induced nitrite production when added to cells up to 4 h after LPS. Thereafter, FNBE caused very little or no reduction in nitrite levels. Furthermore NO-NSAIDs (100 micrograms ml-1) did not inhibit the metabolism of L-[3H]-arginine to citrulline by NO synthase isolated from LPS-activated macrophages. 5. Western blot analysis demonstrated that NO synthase expression was markedly attenuated following co-incubation of J774 cell with LPS (1 microgram ml-1; 24 h) and FNBE (100 micrograms ml-1; 24 h). Thus taken together, these findings indicate that NO-NSAIDs inhibit induction of NO synthase without directly affecting enzyme activity. 6. In conclusion our results indicate that NO-NSAIDs can inhibit the inducible L-arginine-NO pathway, and are capable of suppressing NO synthesis by inhibiting expression of NO synthase. The clinical implications of these findings remain to be established.

Animals↗
PubMed1996

Effects of protein tyrosine kinase inhibitors on cytokine-induced adhesion molecule expression by human umbilical vein endothelial cells.

1. Endothelial cells can be stimulated by the pro-inflammatory cytokines interleukin (IL)-1 alpha and tumour necrosis factor (TNF) alpha to express the leukocyte adhesion molecules E-selectin, vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1 but the intracellular signalling mechanisms leading to this expression are incompletely understood. We have investigated the role of protein tyrosine kinases (PTK) in adhesion molecule expression by cytokine-activated human umbilical vein endothelial cells (HUVEC) using the PTK inhibitors genistein and herbimycin A, and the protein tyrosine phosphatase (PTP) inhibitor sodium orthovanadate. 2. Maximal E-selectin expression induced by incubation of HUVEC for 4 h with IL-1 alpha (100 u ml-1) and TNF alpha (100 u ml-1) was dose-dependently inhibited by genistein and herbimycin A. Although similar effects were seen on phorbol 12-myristate, 13-acetate (PMA)-induced expression, this was not due to inhibition of protein kinase C (PKC) activity as the selective inhibitors of PKC, bisindolylmaleimide (BIM), Ro31-7549 or Ro31-8220 did not affect IL-1 alpha- or TNF alpha-induced E-selectin expression at concentrations which maximally inhibited PMA-induced expression. 3. Genistein inhibited VCAM-1 expression induced by incubation of HUVEC for 24 h with TNF alpha or IL-1 alpha whereas it did not affect ICAM-1 expression induced by 24 h incubation with either of these cytokines. Herbimycin A inhibited both VCAM-1 and ICAM-1 expression induced by TNF alpha. 4. Basal expression of E-selectin, VCAM-1 and ICAM-1 was dose-dependently enhanced by sodium orthovanadate. In contrast, vanadate differentially affected TNF alpha-induced expression of these molecules with maximal E-selectin and ICAM-1 expression being slightly enhanced and VCAM-1 expression dose-dependently reduced. 5. We also studied the effects of PTK and PTP inhibitors on adhesion of the human pre-myeloid cell line U937 to TNF alpha-stimulated HUVEC. Adhesion of U937 cells to HUVEC pretreated for 4 or 24 h with TNF alpha was dose-dependently inhibited by genistein and herbimycin A but unaffected by daidzein. Adhesion of U937 cells after 4 h was partially inhibited by blocking antibodies against both E-selectin and VCAM-1 but after 24 h was only inhibited by anti-VCAM-1. 6. Sodium orthovanadate had no effect on TNF alpha-induced U937 adhesion but dose-dependently enhanced adhesion to unstimulated HUVEC. Vanadate-induced adhesion was inhibited by an antibody against VCAM-1. 7. These results demonstrate that PTK-mediated phosphorylation events are important for the regulation of adhesion molecule expression by human endothelial cells, and additionally show that PTK inhibitors differentially affect upregulation of different adhesion molecules, implicating divergent regulatory pathways for cytokine-induced adhesion molecule expression.

Cell Adhesion Molecules↗
PubMed1995

Increased expression of procoagulant activity on the surface of human platelets exposed to heavy-metal compounds.

One of the essential roles for platelets in haemostasis is in the potentiation of blood clotting due to the contribution of anionic phospholipid from the surface of the cells, as an essential cofactor to the proteolytic reactions of coagulation (platelet procoagulant activity). Only a limited number of agonists are known to initiate platelet procoagulant activity. In this study the rate of thrombin formation on the platelet surface was observed to increase in a dose-dependent manner upon treatment of washed platelets with heavy-metal compounds. Unlike the immediate increase observed upon treatment of platelets with calcium ionophore, A23187, the change due to these agents was progressive, approaching a maximum after 10 min. The maximum-fold acceleration of the rate of thrombin formation compared with control platelets was calculated for HgCl2 (56-fold), AgNO3 (42-fold) phenylmercuriacetate (24-fold) and thimerosal (14-fold), compared with 70-fold observed for calcium ionophore. The increase in procoagulant activity due to HgCl2 coincided with a large increase in intracellular calcium and phosphorylation of 22 and 45 kDa proteins. It is considered that the mechanism responsible for the increase in procoagulant activity is exposure of anionic phospholipids. This was detected by a 2-fold increase in the binding of 125I-annexin V upon addition of HgCl2, compared with resting platelets (3-fold on treatment of platelets with calcium ionophore). In contrast to the generation of activity by A23187 and other known agonists of this reaction, heavy-metal compounds appeared to cause little or no release of microparticles from the platelet surface. Since HgCl2 did not cause aggregation of platelets or significant release of serotinin, these findings may give further support to the need for exposure and ligation of glycoprotein IIb:IIIa for vesiculization to occur. Treatment of platelets with heavy metals may constitute a new approach to investigating the early changes in the cell membrane which lead to increased expression of anionic phospholipid.

Annexin A5↗