Biomedical subjects

L M McManus

Publications and source records attributed to L M McManus.

At least 37 records · Page 2Linked to original sources

PubMed1989

Platelet activating factor in pulmonary pathobiology.

Platelet activating factor (PAF) is a potent phospholipid mediator of inflammation that has been gaining increasing attention because of its pathophysiologic effects upon the lung. In particular, PAF stimulates pulmonary hypertension, ventilatory alterations, bronchoconstriction, airway hyperreactivity, and pulmonary inflammatory cell accumulation and edema in a variety of experimental animals and in humans. These observations promote the speculation that this unique phospholipid likely is involved in similar tissue responses during the course of human lung disease. The use of specific PAF antagonists should expand our understanding of these processes and may be useful in treating or preventing PAF-mediated pulmonary disorders in the future.

Animals↗

PubMed1988

Complement and neutrophil activation in the pathogenesis of ischemic myocardial injury.

Complement depletion with cobra venom factor (CVF) before coronary artery ligation has been previously shown to reduce subsequent ischemic myocardial tissue injury in the baboon; however, whether complement depletion after the initiation of acute myocardial ischemia affords similar myocardial preservation is not known. Both complement depletion with CVF or the administration of certain nonsteroidal anti-inflammatory drugs, including ibuprofen, are thought to decrease myocardial infarct size by reducing polymorphonuclear leukocytic (PMN) infiltration; nevertheless, complement activation also could alter tissue injury by PMN-independent actions. Thus, the relative effects of CVF administered after coronary artery ligation on the subsequent development of myocardial tissue injury were assessed in a baboon myocardial infarction model. The animals were randomized into three treatment groups (n = 6): either CVF (125 units/kg) or saline was given 30 minutes after coronary artery ligation, and ibuprofen (12.5 mg/kg) was administered 30 minutes and 4 hours after ligation. The extent of ischemic myocardial injury was assessed 24 hours later. Relative to saline-treated baboons, both CVF and ibuprofen reduced PMN infiltration (36 +/- 4 vs. 24 +/- 4 and 24 +/- 4 PMN/mm2, respectively; mean +/- SEM) and histological evidence of transmural myocardial infarction (100% vs. 47% and 53%, respectively) in electrocardiographically designated, expected infarct sites. In both saline- and ibuprofen-treated animals, there was extensive localization of C4, C3, and C5 in all infarct sites; in contrast, there was only C4 localization in the CVF-treated baboons. When expected infarct sites were assessed for creatine kinase content as an indicator of tissue injury, there was significantly less epicardial and endocardial creatine kinase depletion in the CVF-treated animals (31.7 +/- 5.6% and 39.3 +/- 4.8%) than in the saline-treated animals (54.1 +/- 5.4% and 59.0 +/- 4.7%; p = 0.012 and 0.011, respectively). The percent creatine kinase depletion in the ibuprofen-treated animals was intermediate between the two other groups. These results suggest that depletion of complement after coronary ligation has beneficial effects in reducing tissue injury that cannot be explained solely on the basis of reducing PMN infiltration into the ischemic myocardium.

Animals↗

PubMed1988

Platelet-activating factor in the rabbit uterus during early pregnancy.

Platelet-activating factor (PAF) concentrations were low in the non-pregnant, oestrous uterus (mean +/- s.e.m.: 2.2 +/- 1.2 pmol/g, n = 3). However, uterine PAF increased dramatically during pregnancy to a maximum of 37.8 +/- 4.90 pmol/g (n = 7) on Day 5. By Day 7, PAF concentrations in the uteri of pregnant rabbits had returned to levels similar to those found at oestrus. In contrast, uterine PAF in pseudopregnant rabbits peaked at 30.6 +/- 2.8 pmol/g (n = 8) on Day 4, declined to 20.5 +/- 2.4 pmol/g (n = 8) on Day 5 and then remained at that concentration through Day 7. Uterine PAF co-migrated with synthetic PAF (1-O-hexadecyl-2-acetyl-sn-glycero-phosphocholine) in both thin-layer and normal-phase high-performance liquid chromatography. PAF activity in the uterus during pregnancy and pseudopregnancy was found almost exclusively in the endometrium; little or no PAF was found in myometrium, uterine flushings or blastocysts. While no PAF was detected in blastocysts on Days 5 and 6 of pregnancy, the presence of the embryo appears to modulate biosynthesis and/or degradation of PAF by the uterus, since PAF decreased significantly in uterine tissue apposed to the implanting embryo (but not in similar areas between such attachment sites). Increased concentrations of PAF in the preimplantation rabbit uterus followed by a dramatic decrease on the day of blastocyst attachment suggest that this potent inflammatory autacoid may play a vital role in implantation.

Animals↗

PubMed1987

Formation of multinucleated cells that respond to osteotropic hormones in long term human bone marrow cultures.

Studies of osteoclasts and their precursors in normal and pathological states have been severely hampered by the lack of an in vitro system for forming osteoclasts. We developed a human marrow culture system in which multinucleated cells with several characteristics of osteoclasts form. Multinucleated cells began to form during the first week of culture, with maximum numbers formed after 3 weeks. PTH (25-50 ng/ml) and 1,25-dihydroxyvitamin D3 (10(-10)-10(-8) M) increased formation of these cells, and these effects were inhibited by calcitonin. These multinucleated cells contained nonspecific esterase and tartrate-resistant acid phosphatase, a marker enzyme of osteoclasts, and had several ultrastructural features of osteoclasts. We used this marrow cell culture technique to study a patient with hyperparathyroidism and markedly increased osteoclasts on bone marrow biopsy. The marrow from this patient formed increased numbers of multinucleated cells in vitro. After parathyroidectomy both multinucleated cell formation in vitro and osteoclast numbers on bone biopsy decreased significantly. This long term marrow culture system represents the first demonstration of human osteoclast-like cell formation in vitro. This system should permit studies to evaluate factors controlling formation of cells with certain osteoclast characteristics in vitro and their precursors as well as to evaluate abnormalities in osteoclast formation in patients with metabolic bone disease.

Bone Marrow Cells↗

PubMed1987

Ontogeny of the responsiveness to intravenous platelet-activating factor.

Neonatal and young animals fail to develop antigen-induced, lethal, systemic anaphylactic reactions. Recent evidence has documented that, in the adult rabbit, an unusual phospholipid autacoid, platelet-activating factor, induces almost all of the physiologic events associated with IgE-induced anaphylaxis. Thus, in the present study, the intravascular alterations after intravenous infusion of synthetic platelet-activating factor (1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine; AGEPC) into young rabbits were examined. In comparison to 13-week-old, adult rabbits, the intravascular infusion of greater than 1.0 micrograms/kg AGEPC was not lethal in rabbits of 8 weeks of age or less. In dose-response studies, the amount of AGEPC required to induce a lethal response in 50% of the animals tested (LD50) was found to inversely correlate with age. In contrast, AGEPC-induced platelet aggregation in vitro was not affected by the age of the donor animal. Consistent with age-independent platelet responsiveness in vitro, AGEPC-induced thrombocytopenia and intravascular accumulation of platelet factor 4 and thromboxane B2 were also unaffected by animal age. Neutropenia and basopenia, as well as platelet and neutrophil sequestration in the pulmonary microvasculature after intravenous AGEPC infusion also were similarly unaffected by animal age. Although the mechanisms which modulate the profound and lethal physiologic responses following AGEPC infusion in the adult rabbit remain to be established, the current study clearly documents an age-dependent acquisition of systemic physiologic sensitivity to AGEPC and/or other mediators released as a result of intravascular AGEPC administration.

Aging↗

PubMed1986

Pathobiology of platelet-activating factors.

Throughout the evolution of knowledge about inflammation, a primary goal has been to understand this important biological response in sufficient depth to prevent the unwanted tissue injury that may spontaneously occur or that may coevolve to produce disease. That is, although the host defense systems normally function in a protective manner, excessive activation or alterations of the homeostatic regulation of the inflammatory responses often results in overt tissue injury and organ dysfunction. Thus, significant attention has been focused upon precise definition of the interactions of the myriad of involved cells and mediators so that interventions may be developed to block these events to prevent and control inflammatory tissue injury. PAF, as a relative newcomer to the investigative eye of experimental pathologists, is a potent proinflammatory mediator of many aspects of the complex host defense system. No doubt, its role in the initiation and maintenance of tissue injury or disease will be conclusively documented with additional research and forthcoming advances in biomedical technology. At present, however, we must be content to accept the conclusion that, while it is tempting to speculate that this unique phospholipid is involved in many different disease processes, unequivocal details to this end are lacking. Nonetheless, the spectrum of antagonists of PAF action which are currently evolving [cf. 95-100] will undoubtedly permit assessment of the putative contributions of PAF to many biological conditions associated with disease. At that time, meaningful conclusions as to the biological role of PAF in human tissue injury and disease may be provided.

Animals↗

PubMed1986

Age-dependent differential development of leukotactic and vasoactive responsiveness to acute inflammatory mediators.

Age-associated development of increased cutaneous vascular permeability and neutrophil accumulation in response to several inflammatory mediators was examined in young rabbits. The development of increased cutaneous vascular permeability was mediator-, age- and dose-dependent and was potentiated by prostaglandin E2 (PGE2). While 4-week-old rabbits responded to bradykinin, they did not develop increased vascular permeability in response to histamine, acetyl glyceryl ether phosphocholine (AGEPC), N-formyl-methionyl-leucyl-phenylalanine, or zymosan-activated plasma at doses which induced significant increases in vascular permeability in 13-week-old rabbits. Dose-dependent increases in vascular permeability after intracutaneous injection of AGEPC and histamine were observed by 6 weeks of age although fewer animals responded to histamine as compared to AGEPC. In addition, coadministration of PGE2 allowed the expression of increased vascular permeability to AGEPC, N-formyl-methionyl-leucyl-phenylalanine and zymosan-activated plasma in all 4-week-old animals. Interstitial neutrophil accumulation as well as increased vascular permeability was also age-, time-, mediator- and dose-dependent. Compared to 13-week-old rabbits, fewer numbers of interstitial neutrophils were observed in 4-week-old animals for up to 4 hours after intracutaneous injection of AGEPC. PGE2 potentiated the neutrophil response to N-formyl-methionyl-leucyl-phenylalanine and zymosan-activated plasma in both young and adult rabbits; nevertheless, the response in young animals was never as extensive as in the adult animal with the exception of the neutrophil infiltrative response after administration of AGEPC and PGE2. These results suggest that PGE2 synthesis and/or reactivity in young animals may be significantly different from adult animals and in part may account for the lowered reactivity to acute inflammatory mediators in the young animal.

Aging↗

PubMed1985

Fast atom bombardment-mass spectrometric identification of molecular species of platelet-activating factor produced by stimulated human polymorphonuclear leukocytes.

Fast atom bombardment mass spectrometry was used to identify molecular species of platelet-activating factor (PAF) produced by stimulated human neutrophilic polymorphonuclear leukocytes. Normal and reverse-phase high performance liquid chromatography were employed to separate the individual regions with PAF activity prior to mass spectrometric analysis. The following alkyl chain homologs of acetyl glyceryl ether phosphorylcholine (AGEPC) were found: C16:0, C17:0, C18:0 and C18:1. There was also evidence for the presence of the C15:0 homolog, as well as other species which have not yet been identified.

Chromatography, High Pressure Liquid↗

PubMed1985

Modulation of platelet-activating factor (PAF) synthesis and release from human polymorphonuclear leukocytes (PMN): role of extracellular albumin.

Human neutrophilic polymorphonuclear leukocytes (PMN) stimulated with N'-formyl-methionyl-leucyl-phenylalanine (FMLP) in the presence of cytochalasin B but in the absence of human serum albumin (HSA) synthesized only small amounts of platelet-activating factor (PAF) that attained maximum levels within 60-120 s after stimulation; in addition, no release of PAF occurred. However, in the presence of 2.5 mg HSA/ml, there was a threefold increase in PAF synthesis, 30-40% of which was released within 5 min after FMLP stimulation. In the presence of 50 mg HSA/ml there was at least a fourfold increase in PAF synthesis and release, with maximal synthesis occurring 10-20 min after stimulation. Thus, the presence of HSA during PMN stimulation not only induced an albumin dose-dependent increase in PAF release but significantly augmented the synthesis of PAF. In contrast to PAF synthesis and release, the presence or absence of HSA had no effect upon lysosomal enzyme secretion from FMLP-stimulated PMN, which was maximal within 30-60s after stimulation. These results demonstrate that HSA plays an essential role in vitro in the synthesis and release of PAF from human PMN, and support the hypothesis that there is a cyclic PAF synthesis-release coupling mechanism in the stimulated human PMN.

Calcium↗

PubMed1985

Participation of platelets in the physiologic alterations of the AGEPC response and of IgE anaphylaxis in the rabbit. Effects of PGI2 inhibition of platelet function.

To further clarify the platelet dependence of acetyl glyceryl ether phosphorylcholine (AGEPC) physiologic activity and of IgE anaphylaxis in the rabbit, PGI2 was employed as an inhibitor of in vivo platelet function. Intravenous infusion of PGI2 (1 to 2 micrograms/kg/min) inhibited the AGEPC-induced decrease in dynamic compliance, increase in total pulmonary resistance, and transient decrease in tidal volume, but the right ventricular hypertension, bradycardia, and apnea were unaffected. Although PGI2 itself produced a marked systemic hypotension, AGEPC still induced a bimodal hypotensive response. Documentation that platelet function was inhibited by PGI2 included partial inhibition of AGEPC-induced thrombocytopenia, abrogation of platelet secretion (as assessed by plasma platelet factor 4 levels), and inhibition of ex vivo platelet aggregation. The AGEPC-induced leukopenia was not affected. In another group of rabbits, chlorpheniramine pretreatment inhibited the lung mechanical changes induced by AGEPC but did not affect the ventilatory or circulatory alterations, indicating that the lung mechanical alterations (but not any of the other alterations) are mediated by platelet-secreted histamine acting via H1 receptors. In IgE-producing rabbits intravenously challenged with antigen, PGI2 had no effect on any of the physiologic alterations, despite substantial inhibition of platelet secretion. From these results, together with previous platelet depletion studies, we conclude that AGEPC may be a significant mediator of the circulatory alterations and apnea of rabbit IgE anaphylaxis by platelet-independent mechanisms, but neither AGEPC nor platelets appear to be important in mediating the anaphylactic lung mechanical alterations.

Anaphylaxis↗

PubMed1985

The role of complement in the pathogenesis of postischemic acute renal failure.

One hour occlusion of total renal blood flow results in oliguric acute renal failure as defined by an abrupt and severe diminution in glomerular filtration rate. In rats, after 1-2 h of such ischemia, the acute renal failure which follows is characterized by decreased renal blood flow and by intratubular obstruction with necrotic cellular debris. The present study has examined the possible role of the complement system in the development of this model of acute renal failure. Immunoreactive C3 was extensively localized within necrotic tubular epithelial cells and the walls of small muscular arteries in reperfused kidneys after 1 h of total renal ischemia. Depletion of complement by the administration of cobra venom factor 18 h prior to the induction of ischemia abrogated C3 localization and significantly attenuated the subsequent fall in renal blood flow following reperfusion but did not alter the oliguria or marked fall in glomerular filtration.

Acute Kidney Injury↗

PubMed1985

Kinetics of acetyl glyceryl ether phosphorylcholine (AGEPC)-induced acute lung alterations in the rabbit.

Acetyl glyceryl ether phosphorylcholine (AGEPC; 1-O-hexadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine) was infused intravenously into rabbits (0.5 micrograms/kg); subsequently, temporal pulmonary alterations were assessed histologically. Within 30 seconds after AGEPC infusion, widespread platelet and neutrophil aggregates were distributed throughout the pulmonary microvasculature. Concomitantly, small muscular arteries and bronchioles throughout the lungs were contracted. Five minutes after AGEPC infusion, intravascular pulmonary platelet aggregates were less frequent and smaller than those observed at 30 seconds after infusion; however, AGEPC-induced pulmonary neutrophil sequestration persisted. Moreover, at this time, large mononucleated cells and damaged endothelial cells were prevalent throughout the pulmonary microvasculature. Sixty minutes after infusion, neither platelet aggregates nor arterial or bronchiolar constriction was observed. However, in most animals, neutrophils and large mononucleated cells were still abundant, and focal endothelial cell alterations persisted. In addition, discrete areas of interstitial hemorrhage around small and medium-sized arteries were present. These studies suggest that the intravascular release of AGEPC could initiate significant pulmonary injury and therefore could be an important etiologic factor in the development of inflammatory lung diseases.

Animals↗

PubMed1984

Molecular heterogeneity of platelet-activating factor produced by stimulated human polymorphonuclear leukocytes.

The molecular heterogeneity of platelet-activating factor (PAF) produced by stimulated human neutrophilic polymorphonuclear leukocytes (PMN) was assessed by both normal and reverse phase high performance liquid chromatography (HPLC). As detected by rabbit platelet stimulation, at least 5 PAF molecules were separated by HPLC. Fast atom bombardment (FAB) mass spectrometry revealed one of these PAFs was acetyl glyceryl ether phosphorylcholine (AGEPC) with a C16:0 alkyl chain in the sn-1 position. Although the structures of the remaining PAFs are unknown, two of the peaks of PAF activity had the same retention times on reverse phase HPLC as the C15- and C18-saturated alkyl chain AGEPC homologues. These studies indicate that the human PMN produces multiple molecular species of PAF.

Amino Acid Sequence↗

PubMed1984

Modulation of platelet-activating factor (PAF) synthesis and release from human polymorphonuclear leukocytes (PMN): role of extracellular Ca2+.

Extracellular Ca2+ regulated the synthesis and release of platelet-activating factor (PAF) from human polymorphonuclear leukocytes (PMN) stimulated with N'-formyl-methionyl-leucyl-phenylalanine (FMLP) in the presence of cytochalasin B. Maximum PAF synthesis and release required the presence of 0.14 mM Ca2+ whereas 1.4 mM Ca2+ was necessary for maximum lysosomal enzyme secretion. The synthesis of PAF occurred within 2.5 min after PMN stimulation in the presence of 1.4 mM Ca2+; however, PAF release did not occur until 5 min after stimulation. Peak PAF release occurred by 7.5 min but accounted for only 30-40% of the total amount of PAF synthesized, the remainder being retained on or within the PMN. Stimulation of PMN in the presence of 0.01 M EDTA or EGTA decreased PAF synthesis and release by greater than 95%. In the absence of extracellular Ca2+, stimulated PMN synthesized PAF in amounts that were 10-30% of maximum, but there was no release of the newly synthesized PAF. At Ca2+ concentrations greater than 0.01 mM, there was a dose-dependent (up to 0.14 mM) increase in PAF synthesis that was associated with the initiation and concomitant increase in the amount of PAF released. These data suggest the presence of a PAF synthesis-release coupling mechanism in which the extracellular Ca2+-dependent release of PAF stimulates additional PAF synthesis.

Adult↗

PubMed1984

Identification and characterization of osteoclast-like cells and their progenitors in cultures of feline marrow mononuclear cells.

The predominant cell responsible for bone resorption, the multinucleated osteoclast, has been difficult to study because of inaccessibility. When feline marrow-derived mononuclear cells are established in long-term culture, multinucleated cells form within 48 h, reaching maximum numbers at 16 d. We have observed that these cultured cells have many of the features of osteoclasts. Morphologically, they are multinucleated, contain large numbers of branched mitochondria, have a peripheral cytoplasm lacking organelles (a clear zone), and have extensive cell-surface processes. In addition to these ultrastructural features, the cells contain a tartrate-resistant acid phosphatase, the activity of which is increased by parathyroid hormone (PTH) and inhibited by calcitonin. PTH, prostaglandin E2, and 1,25(OH)2 vitamin D3 increased multinucleated cell formation, while calcitonin inhibited the stimulatory effects of PTH. Time-lapse cinemicrographic and autoradiographic studies indicated that the multinucleated cells formed by fusion of the mononuclear progenitors. The multinucleated cells were phagocytic and stained with nonspecific esterase, consistent with their being derived from immature monocytes. Further, cell populations enriched for multinucleated cells release 45Ca from devitalized bone. Density-gradient centrifugation on Percoll was used to enrich and characterize the mononuclear progenitors of these multinucleated cells. The progenitor cells were found predominantly in Percoll density layers of 1.065 to 1.08 g/ml and were enriched up to 30-fold as compared to unfractionated cells. The bone marrow mononuclear cells that formed the multinucleated cells were initially nonadherent to plastic, stained heavily with nonspecific esterase, and appeared to be immature monocytes histologically. These data indicate that the multinucleated osteoclast-like cells in our cultures are derived from nonadherent monocytic progenitor cells that are responsive to osteotropic hormones. The ability to grow and characterize these cells in vitro should facilitate studies to elucidate the role these cells play in normal and pathologic states of bone resorption.

Acid Phosphatase↗

PubMed1984

Acetyl glyceryl ether phosphorylcholine (AGEPC). A putative mediator of cardiac anaphylaxis in the guinea pig.

Platelet-activating factor is a novel phospholipid that has been implicated as an important mediator of acute allergic reactions. The intravenous administration of acetyl glyceryl ether phosphorylcholine, a pure, synthetic platelet-activating factor, causes electrocardiographic changes in the rabbit similar to those which are characteristic manifestations of systemic anaphylaxis. To determine whether platelet-activating factor contributes to anaphylactic cardiac dysfunction, we measured platelet-activating factor release from the sensitized guinea pig heart challenged in vitro with specific antigen and compared the resulting cardiac dysfunction with that induced by the injection of acetyl glyceryl ether phosphorylcholine into nonsensitized hearts. The results of these studies document that, during anaphylaxis in the isolated guinea pig heart, a platelet-activating factor is released into the coronary effluent that has physicochemical and functional properties similar to those of acetyl glyceryl ether phosphorylcholine. The intracardiac administration of acetyl glyceryl ether phosphorylcholine (10(-14) to 3 X 10(-9) mol) induced dose-related decreases in left ventricular contractile force (-5 to -85%) and coronary flow (-5 to -85%), as well as impaired atrioventricular conduction. The negative inotropic effect of acetyl glyceryl ether phosphorylcholine also was present in hearts perfused at constant flow. Although, in these hearts, acetyl glyceryl ether phosphorylcholine increased coronary resistance, which may have caused regional shunting and ischemia, it is unlikely that the negative inotropic effect of acetyl glyceryl ether phosphorylcholine was secondary to changes in coronary flow, since acetyl glyceryl ether phosphorylcholine also caused a dose-dependent negative inotropic effect in the electrically paced, noncoronary-perfused left atrium and right ventricular papillary muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaphylaxis↗

PubMed1984

High performance liquid chromatography of platelet-activating factors.

Silica and C18 reverse phase high performance liquid chromatography (HPLC) were used to fractionate synthetic molecular species of 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine (AGEPC) and semi-synthetic platelet-activating factor (PAF) synthesized from beef heart plasmalogens. A single coincident peak from silica HPLC was observed for either a mixture of synthetic AGEPC's with alkyl chain lengths from C12 to C18 or for beef heart-derived PAF. This peak was well separated from other classes of phospholipid standards including 2-lysophosphatidylcholine and 3H-labeled lyso-PAF. Subsequently, the synthetic AGEPC mixture or beef heart PAF was separated into individual species on a C18 reverse phase column. Beef heart-derived PAF was fractionated into at least four molecular species of PAF activity which had similar retention times as the radioactivity of 3H-labeled beef heart PAF. Approximately 56% of the radioactivity of 3H-labeled PAF was found in the fraction with a similar retention time as 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine, 10% as 1-O-octadecyl-2-acetyl-sn-glycero-3-phosphocholine, 11% as 1-O-pentadecyl-2-acetyl-sn-glycero-3-phosphocholine, and 13% in an unidentified fraction which eluted after C-16-AGEPC. The unidentified fraction did not correspond to any of the homologous series of synthetic AGEPCs with saturated alkyl chain lengths from C12 to C18. Recoveries of radioactive phospholipids from silica or reverse phase columns were greater than 95%.

Animals↗

PubMed1984

Morphologic basis of increased vascular permeability induced by acetyl glyceryl ether phosphorylcholine.

The potent vasoactive and leukotactic properties of acetyl glyceryl ether phosphorylcholine (AGEPC) were further characterized histologically. After intravenous infusion of colloidal carbon and local injection of AGEPC, microscopic examination of rat cremaster muscle and skin revealed histamine-like vascular labeling restricted to postcapillary venules. Ultrastructural studies demonstrated subendothelial carbon accumulation in labeled venules. In rat skin, vascular labeling with colloidal carbon was an equally sensitive indicator of AGEPC-induced vasoactivity as was Evans blue dye extravasation for the assessment of AGEPC-induced increased vascular permeability (i.e., 1 pmole of AGEPC consistently initiated both vascular labeling and increased vascular permeability). In addition to its potent vasoactive effects in rabbits and rats, concomitant leukocyte emigration was observed in venules within 15 minutes after intradermal injection of AGEPC. In rabbit skin, AGEPC was equally as potent for the induction of leukocyte infiltrates as for the stimulation of increased vascular permeability. However, the vasoactive properties of AGEPC appeared to be neutrophil independent as well as independent of mast cell and platelet stimulation; these data suggest that AGEPC may act upon the microvasculature by direct stimulation of the venular endothelial cells. Thus, the putative role of AGEPC as a potent inflammatory mediator includes both the vasoactive and the leukotactic aspects of the acute inflammatory process.

Animals↗