兴奋下丘脑弓状核神经元降低大鼠血浆唾液酸水平的作用

实验采用下丘脑弓状核（ＡＲＣ）区微量注射和紫外分光光度测定法,研究ＡＲＣ区注射不同浓度谷氨酸钠（Ｇｌｕ）对大鼠血浆唾液酸（ＳＡ）水平的影响。结果表明：（１）ＡＲＣ区注射Ｇｌｕ后,血浆ＳＡ水平较对照组明显降低（Ｐ〈０．０１）,而且随Ｇｌｕ浓度的增加,血浆ＳＡ水平降低所需的时间逐渐缩短;（２）侧脑室注射阿朴吗啡后,ＡＲＣ区注射Ｇｌｕ,血浆ＳＡ水平明显降低（Ｐ〈０．０１）,而且降低发生时间较对照组提前：     

中药764—3对内毒素所致离体大鼠灌流肺损伤的保护作用探讨

本研究观察了大肠杆菌内毒素对大鼠离体灌流肺的氧化性损伤作用,并探讨了中药７６４－３对该损伤的保护作用。结果发现单纯离体灌流肺给予内毒素刺激未能引起肺动脉升高,这与在体情况下的反应不同。内毒素组的肺泡灌洗液中蛋白质含量和肺组织湿干重比值分别比其它组为高（Ｐ＜０．０５）,该组肺组织匀浆和肺泡灌洗液中丙二醛（ＭＤＡ）含量也显著高于其它组（Ｐ＜０．０１）。中药７６４－３能够显著地减轻肺水肿（Ｐ＜０．０５）     

心肌急性梗塞后心室重构早期心肌线粒体呼吸功能和电子…

结扎大鼠冠状动脉前降支造成急性心肌梗塞（ＡＭＩ）,观察在ＡＭＩ后心室重构早期３、７、１４ｄ心肌线粒体呼吸功能和电子传递组分的改变。结果表明：在心室重构早期,心肌线粒体呼吸ＩＶ态（Ｒ４（明显增高（Ｐ〈０．０２）;呼吸Ⅲ态（Ｒ３）、呼吸控制率（ＲＣＲ）、磷／氧比（Ｐ／Ｏ）、氧化磷酸化速率（ＯＰＲ）明显下降（Ｐ〈０．００１）;呼吸链电子传递组分显著降低（Ｐ〈０．０５或Ｐ〈０．０１）。提示：ＡＭＩ后心室重     

梅花鹿生茸期能量代谢的初步研究

通过呼吸测热试验,结合不同能量进食水平和不同蛋白质水平条件下的消化、代谢试验,对成年梅花鹿生茸期的能量代谢规律进行了研究。结果表明：（１）梅花鹿的产热量（ＨＰ）和体能沉积量（ＲＥ）均随总能食入量（ＧＥＩ）的增加而增加;代谢能转化为体蛋白能和体脂肪能沉积的效率（Ｋｇｐ和Ｋｇｆ）分别为０．５９和０．６１;产热量（ＨＰ）与总能食入量（ＧＥＩ）的回归方程为：ＨＰ（ｋＪ／Ｗ０．７５ｄ）＝２６５．１２＋０．３３２ＧＥＩ（ｋＪ／Ｗ０．７５ｄ）。（２）产热量占总能食入量的百分比（ＨＰ／ＧＥＩ）,无论是在生茸期前期还是在生茸期后期,低蛋白组（ＣＰ为２２．０％）均明显高于高蛋白组（ＣＰ为２９．０％）（Ｐ＜０．０５）,在同一蛋白水平下生茸期前期与后期各组之间无显著差异（Ｐ＞０．０５）;体能沉积量占总能食入量的百分比（ＲＥ／ＧＥＩ）各组之间差异均不显著（Ｐ＞０．０５）;无论在生茸期前期还是在生茸期后期,体蛋白能沉积量占体能沉积量的百分比（ＲＰＥ／ＲＥ）,高蛋白组均高于低蛋白组（Ｐ＜０．０５）,而体脂肪能沉积量占体能沉积量的百分比（ＲＦＥ／ＲＥ）则与其相反（Ｐ＜０．０５）。     

日粮添加塞曼特罗（CIM）对大鼠生长胴体组成及GH水平的影响

选用２４只２月龄ＳＤ处女鼠配对分组,实验组日粮添加１０μｇ／ｇ塞曼特罗（ＣＩＭ）,试验期３０天。与对照组比较,ＣＩＭ显著提高大鼠生长速度（２７．３０％,Ｐ＜０．０１）和胴体比率,降低腰胁部脂肪重,提高腓肠肌、比目鱼肌和趾浅屈肌的鲜重和ＲＮＡ合量及ＰＮＡ／ＤＮＡ值,同时提高大鼠垂体和血清ＧＨ水平分别达３６．７０％（Ｐ＜０．０１）和２３．７７％（Ｐ＜０．０５）,降低血清脲氮含量。表明ＣＩＭ可显著促进大鼠生长,降低体脂含量,促进肌肉肥大,促进蛋白沉积。其作用机理可能还与其促进ＧＨ的合成和分泌有关。     

电针频率对大鼠脊髓灌流液中SOM和CGRP含量的影响

本研究采用放射测定法,分析不同频率电针刺激下大鼠脊髓流液中抑制素（ＳＯＭ０和降钙素基因相关肽（ＣＧＲＰ）放免活性（ｉｒ）的变化。电针频率选择２,１５和１００Ｈｚ,分别收集电针前、中、后各３０ｍｉｎ脊髓灌流液进行测定,实验结果如下：（１）低频（２Ｈｚ）电针使脊髓脊流液中ＳＯＭ－ｉｒ水平升高３９％（Ｐ〈０．０５）,ＣＧＲＰ－ｉｒ降低４７％（Ｐ〈０．０５）;（２）中频电针（１５Ｈｚ）则相反,使ＳＯＭ－ｉ     

实验性肾功能衰竭大鼠血浆中分子物质总量和自由基的变化研究

用腺嘌呤复制动物性慢性肾功能衰竭（ＣＲＦ）模型。观察大鼠血浆血尿素氮（ＢｕＮ）、血肌酐（Ｃｒ）、血红蛋白（Ｈｂ）、超氧化物歧化酶（ＳＯＤ）和中分子物质（ＭＭＳ）总量的变化。结果表明,ＣＲＦ大鼠血浆ＢｕＮ、Ｃｒ和ＭＭＳ总量明显升高（Ｐ〈０．０１）、Ｈｂ和ＳＯＤ含量显著降低（Ｐ〈０．０１）。提示ＣＲＦ大鼠ＭＭＳ总量升高、ＳＯＤ活性降低。     

几种扩血管多肽对bFGF促血管平滑肌细胞增殖作用的影响

目的和方法：研究肾上腺髓质素（Ａｄｍ）、降钙素基因相关肽（ＣＧＲＰ）及Ｃ－型心房利太（ＣＮＰ）对碱性成纤维细胞生长因子（ｂＦＧＦ）促血管平滑细胞（ＶＳＭＣ）增殖作用的影响及其机制。结果：孵育２４ｈ后,ｂＦＧＦ刺激ＶＳＭＣ增殖较对照组增加２．１倍（Ｐ〈０．０１）,细胞内蛋白磷酸化程度增加１．４倍（Ｐ〈０．０１）,ＰＫＣ及ＭＡＰＫ活性分别增加１．５和２．５倍（Ｐ〈０．０１０;Ａｄｍ．ＣＧＲＰｔ ＣＮＰ     

公雏鸡糖皮质激素受体与免疫功能的相关性

研究了用于不同剂量（７５、５０、２５、１０ｍｇ／ｋｇ）ＲＵ４８６阻断公雏鸡糖皮质激素受体１天或连续３天免疫指标变化情况。ＲＵ４８６７５和５０ｍｇ／ｋｇ阻断ＧＲ２４ｈ,公雏鸡脾淋巴细胞ＩＬ－２、ＩＦＮ诱生活性和Ｔ、Ｂ淋巴细胞增殖活性降低（Ｐ〈０．０１）,外周血淋巴细胞、单核细胞、ＡＮＡＥ＋细胞减少（Ｐ〈０．０１）;胸腺、脾脏、法氏囊的体重比减小（Ｐ〈０．０１）。每日ＲＵ４８６５０ｍｇ／ｋｇ连续３天阻     

降钙素基因相关肽拮抗内皮素的致心律失常作用

本工作在麻醉大鼠冠状动脉口注射内皮素１（ＥＴ１）９００ｐｍｏｌ／ｋｇ能引起室性早搏（ＰＶＣ）、室速（ＶＴ）、室颤（ＶＦ）等严重心律失常,心律失常评分（ＡＳ）为５．６±１．０;冠状动脉口单独注射降钙素基因相关肽（ＣＧＲＰ）３００－１２００ｐｍｏｌ／ｋｇ仅引起血压一过性下降,此后逐渐恢复,无心律失常发生,心律失常评分为０。用ＣＧＲＰ３００ｐｍｏｌ／ｋｇ预处理后再注射ＥＴ１９００ｐｍｏｌ／ｋｇ,心律失常发生率减少,严重程度降低,ＡＳ为１．６±１．６。ＣＧＲＰ１２００ｐｍｏｌ／ｋｇ＋ＥＴ１组心律失常评分显著低于ＥＴ１对照组（Ｐ＜０．０１）。本实验结果表明,ＣＧＲＰ的抗心律失常作用很可能有部分是通过拮抗内皮素的致心律失常作用来实现的。     

肠缺血/再灌注损伤后白介素1-β水平与磷脂酶A2激活的关系

为了探讨肠缺血/再灌注损伤后IL-1β基因表达和蛋白含量变化与磷脂酶A2抑制之间的关系,采用大鼠肠缺血/再灌注损伤模型,在对照组,损伤组和磷脂酶A2抑制剂处理组动物中收集血清,肺灌洗液,腹腔灌洗液及全身重要脏器组织样品,采用放射免疫法测定IL-1β含量,并且RT-PCR法测定肺组织中IL-1β和Ⅱ型PLA2基因表达,结果表明,损伤后6h血清中IL-1β含量明显高于对照组;损伤后1和3h,腹腔注保IL-1β也明显高于对照组;损伤后肝组织中IL-1β水平有明显增加,而肺,肾、肠组织中IL-1β没有明显变化。损伤后肺灌洗液中IL-1β也明显高于对照组水平,肺组织中IL-1βmRNA表达增加,而Ⅱ型PLA2mRNA在损伤后表达反而有所下降,采用磷脂酶A2抑制剂氯喹,环氧化物酶抑制剂消炎痛,血小板活化因子受体阻断剂SR27417后,IL-1β蛋白和基因表达有不同的改变,提示肠缺血/再灌注损伤后一定时间内,肝内IL-1βmRNA表达和血中IL-1β水平明显增高,但是否与磷脂酶A2激活或其代谢产物的释放有关尚需进一步证明。     

The release of platelet-activating factor from human endothelial cells in culture

The release of platelet-activating factor (PAF) from stimulated human endothelial cells (HEC) cultured from normal term, umbilical cord veins is described. HEC in primary cultures released PAF after challenge with A23187, rabbit anti-human factor VIII (RaHu/FVIII), angiotensin II, and vasopressin. HEC subcultures maintained the ability to release PAF in the presence of A23187 and RaHu/FVIII, whereas the release of PAF in response to angiotensin II and vasopressin was not constant and was reduced. Control cultured, smooth muscle cells derived from umbilical cord veins, previously depleted of endothelial cells, did not release PAF under the above-mentioned stimulation. Plastic-adherent or cultured monocytes released PAF with A23187, but not with RaHu/FVIII, angiotensin II, and vasopressin. The release of PAF from HEC in primary cultures required the presence of extracellular cations and the activation of membrane phospholipase A2. PAF release induced by A23187, RaHu/FVIII, angiotensin II, and vasopressin was unaffected by indomethacin, an inhibitor of cyclooxygenase, which, however, favored the release of PAF from HEC stimulated with thrombin, a stimulus that did not affect HEC in the absence of indomethacin. PGI2 inhibited PAF release from stimulated HEC. The relevance of an acetylation process in the biosynthesis of PAF and HEC was supported by the following evidence: 1) the increase in PAF yield in the presence of sodium acetate and, particularly, of acetyl-CoA; 2) the incorporation of [14C]acetate into PAF molecules; 3) the loss of radioactivity and of biologic activity after treatment with phospholipase A2. These results indicate that HEC in culture are able to release PAF and that metabolic pathways similar to those described for leukocytes are involved.     

Purification of rabbit platelet secretory phospholipase A2 and its characteristics

It was reported previously that rat platelets release phospholipase A2 upon in vitro stimulation by thrombin, ADP, or A23187 (Horigome, K., Hayakawa, M., Inoue, K., & Nojima, S. (1987) J. Biochem. 101, 53-61). Secretion of phospholipase A2 was also observed with rabbit platelets. Rabbit platelets seem to release phospholipase A2 upon stimulation in vivo, because the rabbit plasma taken immediately after intravenous injection of PAF contained an appreciable level of phospholipase A2 activity and fewer platelets. Rabbit platelet phospholipase A2 released in vitro was purified by column chromatography using Sepharose CL-4B conjugated with anti-rat platelet derived phospholipase A2 monoclonal antibody, followed by reversed-phase HPLC. The purified enzyme was subjected to structural analysis by HPLC peptide mapping and primary sequence determination of the separated peptides. Based on the homology with rat platelet secretory phospholipase A2 (Hayakawa, M., Kudo, I., Tomita, M., Nojima, S., & Inoue, K. (1988) J. Biochem. 104, 767-772), a partial primary structure (62 amino acid residues) of the rabbit enzyme was tentatively determined; the two sequences were highly homologous (72%). The rabbit sequence was also nearly identical to that of rabbit ascitic fluid phospholipase A2, which was determined by Forst et al. (Forst, S., Weiss, J., Elsbach, P., Maraganore, J.M., Reardon, I., & Heinrikson, R.L. (1986) Biochemistry 25, 8381-8385). Phospholipase A2 from the membrane fraction of rabbit platelets was also purified; it had the same characteristics and th same amino-terminal sequence as the purified secretory enzyme. Secretory and membrane-bound phospholipase A2 of rabbit platelets may in fact be identical.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of aminophylline and ketotifen in comparison to the lipoxygenase inhibitors NDGA and esculetin and the PAF antagonists WEB 2170 [correction of 2107] and BN 52021 on endothelin-1 induced vaso- and bronchoconstriction.

Theophylline (p less than 0.05) and ketotifen (p greater than 0.05) markedly reduced, but the lipoxygenase inhibitors and PAF receptor antagonists were without any influence on the endothelin-1 (ET-1 1 nmol/kg i.v.) induced increase of pulmonary inflation pressure of anaesthetised and ventilated guinea-pigs. The ET-1 induced increase in mean arterial blood pressure as well as the secondary TXB2 release into bronchoalveolar lavage fluid or plasma was not decreased. TXB2 release cannot be the only mechanism of bronchopulmonary ET-1 effects in guinea-pigs in vivo.     

Hypoxia primes endotoxin-induced tissue factor expression in human monocytes and endothelial cells by a PAF-dependent mechanism

Tissue factor (TF) is a glycoprotein which acts as a trigger of the coagulation cascade. TF expression may be induced at the surface of monocytes and endothelial cells by several stimuli including bacterial endotoxin (LPS) and cytokines (IL1β, TNFα) and there is a large body of evidence for the involvement of hypoxia as a primaring factor in the process leading to thrombosis. To define the molecular basis underlying this phenomenon, we evaluated the relative role of platelet activating factor (PAF). PAF primed human monocytes and human umbilical vein endothelial cells (HUVEC) for TF expression following exposure to E. coli LPS but was unable to enhance the induction of TF expression by IL1β. The priming effect of PAF with regard to LPS occurred in a time-and dose-dependent manner and was inhibited by the PAF receptor antagonist SR 27417. When HUVEC or monocytes were exposed to an hypoxic environment, a significant rise in LPS-induced TF expression was observed. Hypoxia had no effect on IL1-induced TF expression. The enhanced LPS-induced TF expression in both cell types was mediated by PAF as indicated by the inhibition obtained with SR 27417, added during hypoxia. Although the importance of hypoxia in the etiology of venous thrombosis has been acknowledged for a long time, evaluation of the relative importance of PAF in the process leading to thrombus formation is still lacking. Stasis-induced thrombosis performed in the rabbit jugular vein was enhanced in a dose-dependent manner by the prior i.v. administration of LPS (0.05 to 100 μg/kg, i.v.). SR 27417 administered simultaneously with LPS prevented thrombus formation with an ED50 value of 0.1 ± 0.04 mg/kg. These results therefore show that hypoxia promotes LPS-induced TF expression in HUVEC and human monocytes through a PAF-dependent mechanism in vitro and in vivo. © 1996 Wiley-Liss, Inc.     

Protein kinase C activity appears to be required for the synthesis of platelet-activating factor and leukotriene B4 by human neutrophils

Human neutrophils synthesize platelet-activating factor (PAF) and leukotriene B4 (LTB4) when stimulated with the Ca2+ ionophore A23187. These processes are enhanced to a variable extent by phorbol 12-myristate 13-acetate (PMA), a direct activator of protein kinase C. The long chain amines sphingosine, stearylamine (Hannun, Y.A., Loomis, C.R., Merrill, A.H., Jr., and Bell, R.M. (1986) J. Biol. Chem. 261, 12604-12609), and palmitoylcarnitine competitively inhibit activation of purified protein kinase C in vitro and inhibit protein kinase C-mediated activation of the respiratory burst in human neutrophils (Wilson, E., Olcott, M.C., Bell, R.M., Merrill, A.H., Jr., and Lambeth, J.D. (1986) J. Biol. Chem. 261, 12616-12623). These amines were found to inhibit A23187-induced PAF and LTB4 synthesis. Inhibition of PAF and LTB4 synthesis occurred in parallel; half-maximal inhibition by sphingosine occurred at 7 microM, with complete inhibition at 15 microM. PMA by itself did not induce the synthesis of PAF or LTB4, although it did enhance PAF and LTB4 synthesis at suboptimal concentrations of A23187. PMA reversed long chain amine inhibition of PAF and LTB4 accumulation. Reversal of the inhibition of PAF and LTB4 accumulation occurred in parallel, was concentration-dependent, and was complete by approximately 3 x 10(-8) M PMA. The inactive 4 alpha-phorbol didecanoate ester did not reverse inhibition at these concentrations. Sphingosine completely prevented the A23187-induced release of [3H]arachidonate and its various metabolites from [3H]arachidonate-labeled cells. PMA, but not 4 alpha-phorbol didecanoate, restored arachidonate release and its metabolism. Therefore, while activation of protein kinase C is not sufficient to induce PAF and LTB4 synthesis, its action appears to be required to couple a rise in intracellular Ca2+ to their synthesis. This coupling occurs at the level of the initial reaction in the production of lipid mediators, a phospholipase A2-like activity that mobilizes the two substrates 1-O-alkyl-sn-glycero-3-phosphocholine and arachidonic acid from complex lipids.     

Defining the role of protein kinase c in calcium-ionophore-(A23187)-mediated activation of phospholipase A2 in pulmonary endothelium.

We sought to investigate the mechanisms by which the calcium ionophore A23187 triggers arachidonic acid release in bovine pulmonary endothelial cells and to test the hypothesis that protein kinase C is involved in this process. Our results indicate that the mechanism by which A23187 increases phospholipase A2 activity and arachidonic acid release in bovine pulmonary arterial endothelial cells depends upon the concentration studied. At concentrations of 1 microM and 2.5 microM, A23187 increases phospholipase A2 activity and arachidonic acid release without stimulating protein kinase C. At concentrations of 5-12.5 microM, A23187 increases arachidonic acid release and phospholipase A2 activity in conjunction with a dose-dependent activation of membrane-bound protein kinase C. To test the hypothesis that these doses of A23187 increase phospholipase A2 activity by stimulating protein kinase C, we studied the effect of prior treatment with the protein kinase C inhibitor sphingosine. Sphingosine inhibits the increase in phospholipase A2 activity and arachidonic acid release caused by A23187 over the range 5-12.5 microM. To investigate further the potential role of protein kinase C, we studied the effects of the inactive phorbol ester 4 alpha-phorbol 12 beta-myristate 13 alpha-acetate (4 alpha-PMA) and an active phorbol ester 4 beta-phorbol 12 beta-myristate 13 alpha-acetate (4 beta PMA). Neither 4 alpha-PMA nor 4 beta-PMA affected basal arachidonic acid release. 4 alpha-PMA also did not augment the effects of A23187. In contrast, 4 beta-PMA significantly augments the increase in phospholipase A2 activity and arachidonic acid release caused by lower doses of A23187. Under these conditions, sphingosine completely inhibits the stimulatory effects of 4 beta-PMA on protein kinase C translocation, phospholipase A2 and arachidonic acid release. Thus, at low doses (1 microM and 2.5 microM) A23187 increases phospholipase A2 activity and arachidonic acid release by a mechanism that does not involve protein kinase C. At these A23187 doses, activating membrane-bound protein kinase C with 4 beta-PMA causes a synergistic increase in phospholipase A2 activity and arachidonic acid release. At higher doses (5-12.5 microM), A23187 acts in large part by stimulating protein kinase C translocation. Overall, our results indicate that activating membrane-bound protein kinase C by itself is an insufficient stimulus to increase phospholipase A2 activity and arachidonic acid release in pulmonary endothelial cells, but activating protein kinase C can substantially augment the increase in phospholipase A2 activity and arachidonic acid caused by a small increase in intracellular calcium.     

Mechanism of increased angiotensin-converting enzyme activity stimulated by platelet-activating factor

We studied the effects of platelet activating factor (PAF) on angiotensin-converting enzyme (ACE). PAF (1 x 10(-10) to 1 x 10(-6) M) had a novel effect on angiotensin I conversion. Pulmonary artery endothelial cells converted 1 nmol/dish of 125I-angiotensin I to angiotensin II in the absence of PAF. ACE activity was increased to 2.5 nmol/dish by the addition of 1 x 10(-6) M of PAF. To clarify the mechanism of this stimulatory effect of PAF on ACE, Ca2+ influx and inositol 1,4,5-trisphosphate (IP3) release in pulmonary artery endothelial cells were determined. PAF stimulated Ca2+ influx in a dose-dependent manner. PAF also stimulated phospholipase C (PLC) activity and released IP3. To study the relationship between PLC activity and ACE activity, neomycin was added. The Ca2+ influx and IP3 release stimulated by 10(-6) M of PAF were suppressed by about 60-70%. ACE activity was also inhibited up to 70% in the presence of PAF (10(-10) - 10(-6) M) by 50 M of neomycin. These results suggest that ACE was stimulated by PAF, and that its activity in endothelial cells may be mediated by the PI-turnover pathway via changes in PLC activity and IP3-mediated Ca2+ release from intracellular stores.     

Phospholipase A2-mediated release of arachidonic acid in stimulated guinea pig alveolar macrophages: interaction with lipid mediators and cyclic AMP

The stimulation of cultured guinea pig alveolar macrophages by the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine, or by the phospholipid inflammatory mediator platelet activating factor (PAF) induced an increase in arachidonic acid release and its cyclooxygenase products. This release, which was mimicked by the association of threshold concentrations of the calcium ionophore A 23187 and of the protein kinase C activator tetradecanoyl phorbol acetate arose mainly from diacyl- and alkyl-acyl-phosphatidylcholine and phosphatidylinositol. Using [1-14C]arachidonic acid-labeled membranes as an endogenous substrate as well as dioleoyl-phosphatidyl [14C]ethanolamine as an exogenous substrate, we showed that phospholipase A2 activity of stimulated macrophages increases upon stimulation. Treatment of macrophages by prostaglandin E2 decreased the arachidonic acid release elicited by the chemotactic peptide and PAF. Furthermore, prostaglandin E2 increased and PAF decreased the cellular content in cyclic AMP. From these results we suggest that an initial stimulation of alveolar macrophages by a bacterial signal initiates the sequential activation of a phospholipase C and of phospholipase A2, leading to the release of PAF and eicosanoids. These mediators may in turn modulate the cell response by increasing or decreasing cyclic AMP, Ca2+, or diacyglycerol macrophage content.     

Meconium enhances platelet-activating factor and tumor necrosis factor production by rat alveolar macrophages

Meconium aspiration syndrome (MAS) frequently results in inactivation of surfactant, persistent pulmonary hypertension (PPHN) and respiratory failure among newborn infants. Inflammation and inflammatory mediators play an important role in MAS. Since alveolar macrophages are thought to be very important cells in the pathogenesis of various inflammatory diseases, we evaluated whether meconium could stimulate rat alveolar macrophages to generate platelet-activating factor (PAF) and tumor necrosis factor (TNF)-alpha in vitro. We also examined the response to A23187 (calcium ionophore), 1-0-Hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (synthetic PAF) and dexamethasone on meconium-induced release of PAF and TNF-alpha. PAF and TNF-alpha concentrations from supernatant fluid were measured after high-performance liquid chromatography purification by specific radioimmunoassay, and TNF-alpha concentrations were determined by using an enzyme-linked immunosorbent assay. Our results showed that alveolar macrophages exposed to meconium could enhance PAF and TNF-alpha production in a dose (0.1, 1, 5 and 10%, P<0.01)-dependent way. In the presence of A23187, the capability of meconium to stimulate PAF production was further enhanced in the supernatant fluids. Furthermore, treatment with synthetic PAF significantly increased the generation of TNF-alpha in response to meconium. On the other hand, dexamethasone effectively inhibited both PAF and TNF-alpha production stimulated by 5% meconium (P<0.01, P<0.01; respectively). We suggest that alveolar macrophages and PAF, TNF-alpha play an important role in the pathogenesis of lung injury and severe complications in MAS. Furthermore, the protective effect of glucocorticoids in MAS could be due, at least in part, to a suppression of PAF and TNF-alpha generation.