Platelet activating factor, PAF, was originally identified as a product released by antigen-stimulated, IgE-sensitized rabbit basophils. The chemical structure of PAF is 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine. PAF has a wide spectrum of potent biological activities. In addition to the platelet activation, PAF produces constraction of smooth muscle, cardiac effects, or increase of vascular permeability. PAF induces aggregation, chemotaxis, and active oxygen generation in neutrophils. It also induces monocytes aggregation, eosinophil chemotaxis, and macrophage activation. PAF has a strong hypotenive action. PAF is generated, by an appropriate stimulation, from basohils, monocytes-macrophages, polymorphonuclear leukocytes, platelets, or endothelial cells. Several organs including lung and kidney were also demonstrated to produce PAF.
PAF is present as a precursor; alkylacyl GPC in cell membrane, and synthesized upon stimulation. So far two routes of PAF biosynthesis have been considered; acetylation of lyso PAF catalyzed by “acetyltransferase” and cholinephosphorylation of alkylacetylglycerol by “cholinephosphotransferase”. Inactivation of PAF is mainly catalyzed by “acetylhydrolase”, to yield lyso PAF, which is often converted to alkylacyl GPC.
Although the precise role of PAF in vivo has not yet been fully understood, it is becoming increasingly evident that PAF is important in some physiological and pathological reaction, such as gram-negative septic shock, inflammation, asthma, and nephritis. In the present review, we describe the outline of development of PAF research based on biological, physiological, and pathological aspects.

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We have previously reported that calcium channel blockers interfere with the chemotaxis of guinea-pig PMNs. The concentrations required for inhibition of PMN chemotaxis are usually one or two orders of magnitude higher than those necessary for inhibition of calcium ion translocation across smooth muscle cell membranes. These compounds possess a calmodulin inhibitory property at relatively high concentration. In the studies reported herein, we examined the possible role of calmodulin in the chemotaxis of guinea-pig PMNs using calmodulin inhibitors. Calmodulin inhibitors, N- (6-aminohexyl) -5-chloro-1-naphthalene sulfonamide (W-7), trifluoperazine (TFP) and chlorpromazine (CPZ), suppressed the PMN chemotaxis in a dose-dependent manner. N- (6-aminohexyl) -1-naphthalene sulfonamide (W-5) TFP-sulfoxide and CPZ-sulfoxide, which have very low affinity for calmodulin, had practically no inhibiting effect on the PMN chemotaxis. Calmodulin inhibitors also inhibited the PMN chemotaxis in the absence of extracellular calcium ions. These results suggest that calmodulin plays some role in the chemotaxis of neutrophils.

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Leukotriene D₄-metabolizing activity was studied using human neutrophils. Leukotriene D₄ was rapidly converted to leukotriene E₄ during incubation with intact neutrophils. The subcellular localization of leukotriene D₄-metabolizing enzyme was examined, and leukotriene D₄-metabolizing activity was found to be present in the particulate fraction which consists of cell surface membrane and granules, but not in the nuclear and cytosol fractions. When neutrophils were modified chemically with diazotized sulfanilic acid, a poorly permeant reagent which inactivates cell surface enzymes selectively, the leukotriene D₄-metabolizing activity of intact neutrophils was significantly inhibited. When neutrophils were stimulated with phorbol myristate acetate, a secretagogue, leukotriene D₄-metabolizing activity was found to be released extracellularly. Among enzyme inhibitors examined, o-phenanthroline, a metal chelator strongly inhibited both the leuko-triene D₄-metabolizing activities of intact neutrophils and extracellularly released enzyme. These results would suggest that leukotriene D₄-metabolizing metalloenzymes which convert leukotriene D₄ to leukotriene E₄, are located on the cell surface membrane and in the granules of human neutrophils.

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To clarify the vasoconstrictory action of leukotriene D₄ (LTD₄) on the injured coronary arteries, 8 mongrel dogs were denuded by basket balloon catheter (denuded group) and LTD₄ (0.33μg) was directly administered into left anterior descending coronary artery. Hemodynamic parameters as well as epicardial ECG were recorded after LTD₄ administration. Another 8 non-denuded dogs were served as control.
Furthermore, the influence of denudation to LTD₄-induced coronary spasm was determined by coronary arteriography (CAG) . In results, a significant reduction of coronary blood flow (from 1.03±0.13 to 0.49±0.05 ml/kg/min. P<0.01) and a significant increase of coronary vascular resistance (from 6.5±1.0 to 12.7±2.5 mmHg/ml/min. P<0.01) concomitant with a marked prolongation of ST segment elevation on epicardial EGG (duration time 439±86 sec) were observed in denuded group as compared with non-denuded group. And, the exaggeration of LTD₄-induced coronary spasm at the site of denudation was documented by GAG.
These results suggested that the vasoconstrictory action of LTD₄ was exaggerated on the injured coronary arteries and which might play an important role of pathogenesis and deteriolation of myocardial ischemia.

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Renal function is modulated by glomerular mesangial cells which react to many substances. Arachidonic acid metabolites are important not only for the inflamation of glomeruli, but also for the regulation of renal function. We studied on arachidonic acid metabolism in the cultured rat mesangial cells.
Glomeruli isolated from 150g male Sprague-Dawley rats were treated with collagenase and trypsin and cultured in supplemented nutrient medium for 28 days. Experiments were perforemed on the first passage. Prostaglandins (PGsE) E₂, F₂α, D₂ 6-oxo-PGF₁α, and Thromboxane B₂ (TXB₂) were measured by gas chromatography-masspectrometry (GC-MS) .
The mesangial cells produced PGE₂>PGF₂α>>PGD₂, 6-oxo-PGF₁α, and TXB₂. Arginine vasopressin and angiotensin II stimulated PGE₂ and PGF₂α synthesis. High osmolaity condition by glucose or mannitol stimulated all PGs synthesis, especialy PGE₂ and PGD₂ when incubated with arachidonic acid.
These results suggest that mesangial PGE₂ and PGD₂ are important for the modulation of glomerular function.

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Changes of endogenous opioid peptide system by pain stimuli were examined using adjuvant-induced arthritic rats. Following the 5th day after adjuvant inoculation, the met-enkephalin-like peptide content in plasma was significantly decreased while after the 12th day, the peptide content was markedly increased in adrenal medulla. Significant correlationships were found between pain threshold and met-enkephalin-like peptide contents in adrenal medulla and plasma. It was suggested that a long term of lowering of plasma opioid peptide level was necessary to lower the pain threshold, and was followed by compensatory promotion of the opioid peptide processing in adrenal medulla. Y-20003, a new nonsteroidal antiinflammatory agent without inhibition of prostaglandin biosynthesis, showed an analgesic effect which was significantly antagonized by naloxone or Win 44, 441-3, suggesting that the endogenous opioid peptide system may be involved in the analgesic mechanism of Y-20003.

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We prepared 9 types of indomethcin gel and cream ointments cotaining lecithin (ELT), benzyl nicotinate (NB), collagen or β-cyclodextrin as a stimulant of the absorption of indomethacin. Analgesic and anti-inflammatory effects of these ointments were studied comparing with Inteban (Sumitomo, Co. Ltd.) after topical application of the skin. Inhibitory effect of AN-15 containing 1% indomethacin, 2% ELT and 0.1% NB was the best among the others and equal to Inteban on carrageenin-induced potentiation of vascular permeability and ultraviolet ray-induced erythema in the guinea pig skin. On ultraviolet ray-induced erythema, when a term of ultraviolet ray exposure was prolonged, AN-15 was more potent than Inteban, and AN-2 containing half the indomethacin concentration of AN-15 had a equal effect of AN-15 and Intedan. Inhibitory effect of AN-15 and AN-2 were equal to Inteban on adjuvant arthritis in rats. AN-15, AN-2 and Inteban inhibited hyperalgesia significantly in adjuvant arthritic rats. From these facts, it is concluded that AN-15 is equal to or more potent than Inteban in anti-inflammatory and analgesic action, and the addition of NB and ELT for stimulation of indomethacin absorption is effective.

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The action mechanism of three kinds of Chinese herbs, BG-102, BG-103 and BG-104 was investigated. The activity of methyltransferase and phospholipase A₂ of human in vitro leukeocyte membranes which induce cell activation, and ethanolamine base-exchange activity which has been recently found to be a precursor of transmethylation were assessed. Further, the effect of the drugs on lipoxygenase activity of rat basophilic leukemia cells, prostaglandin release from human leukocytes and oxygen radicals (O^-₂, H₂O₂, OH⋅, chemiluminescence) generated in both neutrophils and xanthine-xanthine oxidase system. The results revealed that although any drug did not change the activity of methyltransferase, phospholipase A₂ or ethanolamine-exchange of healthy human leukocytes, increased activity of these three enzymes induced by the addition of opsonized-zymosan (for neutrophils) or Con A (for lymphocytes), or found in the acute stages of the paients with various inflammatory disorders such as Behçet's disease, RA, bacterial infections, etc. was reduced to near the basal levels. Three herbs also decreased all oxygen radicals generated in two oxygen radical generating systems. On the other hand, lipoxygenase activity or prostaglandin release was not affeced by any of these Chinese herbs. These findings suggest that these drugs are effective insubsiding the excited situations of inflammatory cells, stabilizing the inflammatory cell membranes and that they have oxygen radical scavenger activity and act as antiinflammatory agents.

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The purpose of this study was to evaluate the immunohistochemical localization of prostaglandin E (PGE) in rat carrageenin granuloma, comparing with the quantitative contents of PGE determined by the radioimmunoassay in our previous study. The contents of PGE in the previous, quantitative study was the highest after 3 days of the carrageenin injection. Numerous macrophages were observed at that time and the most of them were intensely stained for PGE in this study. The number of macrophages, however, were markedly decreased and the staining intensity for PGE were almost inhibited in indomethacin-treated group. These results suggest that the intensity of immunohistochemical staining for PGE is correlated with the biochemical, quantitative result of PGE.

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We measured amount of tissue kallikrein of gastric mucosa in 39 patients of chronic gastritis by sandwich type enzyme linked immunosorbent assay (S-ELISA) . Amount of tissue kallikrein was 9.1±4.4 ng/g tissue (mean±S.E.) in gastric mucosa of gastric glands, and was about twenty five times as much as it in the parts of atrophic gastric mucosa of them. The quantity of kallikrein was in proportion to age and the extent of atrophic gastritis. It was speculated that tissue kallikrein would participate in inflammatory atrophic change of gastric mucosa in chronic gastritis.

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