[Studies on chemical constituents in the fruit of Canarium album Raeusch]

OBJECTIVE

To study the chemical constituents in the fruit of Canarium album.

METHOD

Compounds were isolated by chromatography and elucidated on the basis of spectroscopic analysis.

RESULT

The compounds obtained were determined as scoparone, scopoletin, (E)-3,3'-dihydroxy-4,4'-dimethoxystilbene and gallic acid.

CONCLUSION

All the compounds, except gallic acid, were obtained from this plant for the first time.

[The effects of moderate acute normovolemic hemodilution on intestinal oxygen supply and consumption in anesthetized cats]

OBJECTIVE

To study the effects of moderate acute normovolemic hemodilution on the intestinal blood perfusion and oxygen supply in cats.

METHODS

15 domestic male cats were hemodiluted with Haemaccel. HR, MAP, lactate concentration in superior mesenteric vein (LAC), superior mesenteric artery blood flow (SMABF), superior mesenteric artery and venous blood gas analysis were recorded and the intestinal oxygen delivery (DO(2)), oxygen consumption (VO(2)) and oxygen extraction (EO(2)) were calculated before and after hemodilution.

RESULTS

SMABF increased obviously (P < 0.05), intestinal DO(2) and EO(2) did not change (P > 0.05) but VO(2) increased (P < 0.05), and LAC in superior mesenteric vein did not increase.

CONCLUSIONS

Moderate acute normovolemic hemodilution with Haemaccel do not alter intestinal oxygen delivery by increasing the superior mesenteric blood flow. It means that intestinal mucosa ischemia does not happen during moderate acute normovolemic hemodilution.

Role of a novel KCa opener in regulating K+ channels of hypoxic human pulmonary vascular cells

Hypoxic pulmonary vasoconstriction (HPVC) is mediated, in part, via membrane depolarization and inhibition of K+ channels. We recently observed that the naturally occurring steroid dehydroepiandrosterone (DHEA) reversed and prevented HPVC in isolated perfused and ventilated ferret lungs. In the current study, we investigated the effects of DHEA on the major K+ channels of chronically hypoxic human pulmonary smooth-muscle cells (HPSMC). K+ channels were recorded by using the patch-clamp technique in whole-cell and single-channel configurations. Single-channel recordings were performed in inside-out and outside-out excised patches, and in intact HPSMC in cell-attached configuration. Using whole-cell current recording, chronic hypoxia decreased the high-amplitude, high-noise, and charybdotoxin-sensitive Ca2+-dependent K+ channels (KCa). DHEA reversed the effect of chronic hypoxia on KCa, but had no effect on the low-amplitude, low-noise, and 4-aminopyridine-sensitive delayed rectifying K+ channels. In the cell-attached configuration, chronic hypoxia caused a decrease in KCa sensitivity to membrane potential (Em). DHEA reversed the effect of hypoxia on KCa sensitivity to Em and caused a mean of 40-mV left shift in voltage-dependent activation of KCa. DHEA increased KCa activation from both sides of membrane patches of hypoxic HPSMC via a cyclic adenosine monophosphate- and cyclic guanosine monophosphate-independent pathway. We concluded that DHEA is a novel KCa opener of the human pulmonary vasculature.

[Trace analysis of Zn-doped compound semiconductor material by resonant ionization mass spectrometry]

An experimental setup and the procedure for the laser resonant ionization mass spectrometry (RIMS) have been described. Both an optical spectrum and a mass spectum have been shown. The detection limit that can be reached by using this procedure has been estimated.

Studies on biosensor to determine diacetyl

We studied the purification of diacetyl reductase, the preparation of a biosensor, and its performance. With diacetyl reductase and reduced coenzyme I (NADH) co-immobilized as working membrane, NAD+/NADH produced in the course of diacetyl reduction was connected with Fe2+/Fe to build a biosensor. The biosensor could be used to determine diacetyl concentration within the range from 0.1 microgram/mL to 0.5 microgram/mL and the response time was less than two minutes, and its performance was stable within 9 days. The experiments showed that typical metal ions and organics in nominal concentration did not affect the performance of the biosensor, meanwhile, the interference of dissolved oxygen on the performance of biosensor and regeneration of coenzyme I (NADH) were solved to some extent.

[A 5-year follow-up study of antiviral effect of interferon in patients with chronic hepatitis C]

In order to discuss the anti-viral effects of IFN alpha-2a and IFN alpha-2b on chronic hepatitis C in a short and long period of time after treatment, 70 cases of chronic hepatitis C treated with IFN alpha-2a, 46 cases with IFN alpha-2b and 28 cases as controls had been investigated in this study. The follow-up time began from half to 5 years. The serum negative conversion rate of HCV RNA and the normalization of serum alanine transaminase(ALT) were detected at the end of treatment and up to 5 years after therapy. The negative seroconversion rate of HCV RNA and the serum ALT normalization were 67.14% and 70.00% respectively in IFN alpha-2a group and 69.56%, 71.71% respectively in IFN alpha-2b group at the end of the treatment. After 5-year follow-up, the above two Indexes were 35.71%, 47.14% respectively in IFN alpha-2a group, and 39.13%, 52.17% respectively in IFN alpha-2b group. The effectiveness in treated patients was higher than that of controls (P < 0.01 and P < 0.05). Recombinant IFN alpha-2a and IFN alpha-2b are effective medicines for HCV infection. And interferon therapy had a high short-term complete response but a low long-term complete response in the treatment of chronic hepatitis C. HCV genotype seems to be an important factor in determining the response rate of IFN treatment in patients with chronic hepatitis C.

[Change of hymodynamics and circulating endothelial cells in chronic obstructive pulmonary diseases (COPD) and cor pulmonale patients]

OBJECTIVE

To investigate the vascular endothelial injuries by observing the changes of circulating endothelial cells (CEC) numbers in blood and hemodynamics in COPD and cor pulmonale patients.

METHOD

The arterial catheterion technique and CEC collection technique were used, superoxide dismutase (SOD) and malondialdyhyde(MDA) levels were determined respectively.

RESULT

mPAP (3.76 +/- 0.75 kPa) and CEC (16.70 +/- 2.65/0.9 microliter), MDA (6.98 +/- 1.47 mumol/L) in the chronic cor pulmonale are higher than that of mPAP (2.09 +/- 0.41 kPa) and CEC (8.48 +/- 2.23 microliters) in COPD, the numbers of CEC are adversely correlated to PaO2 (gamma = 0.9423, P < 0.001) and positively correlated with mPAP (gamma = 0.8270, P < 0.001), superoxide dismutase(SOD) was decreased.

CONCLUSION

mPAP, CEC are higher in cor pulmonale than that in COPD, CEC numbers rise when the PaO2 was lowered, hypoxia may worsen the vascular endothelial injuries.

ET-1 modulates KCa-channel activity and arterial tension in normoxic and hypoxic human pulmonary vasculature

The molecular mechanisms by which endothelin (ET)-1 induces pulmonary hypertension are poorly understood. We investigated the effects of ET-1 on outward K+ currents of normoxic and chronically hypoxic human pulmonary arterial (PA) smooth muscle cells (HPSMCs). In normoxic HPSMCs, ET-1 has dual effects. In intact cells, 5 nM ET-1 activates the large-conductance and Ca2+-activated K+ (KCa)-channel current [IK(Ca)] by increasing intracellular Ca2+ concentration, whereas it directly inhibits IK(Ca) in isolated membrane patches. At a higher concentration (10 nM), ET-1-induced IK(Ca) inhibition predominates. In hypoxic HPSMCs, ET-1 at 5 nM significantly reduces IK(Ca). The ETA-receptor antagonist BQ-123 reverses the ET-1-induced decrease in IK(Ca). Chronic BQ-123 treatment also prevents the hypoxia-induced decrease in IK(Ca). In PA rings obtained from human organ donors, ET-1 causes a concentration-dependent increase in tension. The ET-1-mediated increase in tension is reversed by a KCa-channel agonist. The increase in tension at the highest concentration studied (9 nM) was more pronounced in PA rings obtained from patients with chronic obstructive pulmonary disease. These results imply that an ET-1-induced decrease in IK(Ca) contributes to chronic hypoxia-induced pulmonary hypertension.

Genetic variation in sympatric Ascaris populations from humans and pigs in China

It has recently been shown using genetic markers that Ascaris in humans and pigs in Central America comprise reproductively isolated populations. We present a similar analysis for a region of China in which close association between pigs and humans has been the norm for thousands of years, and agricultural practices will result in frequent exposure to eggs from both sources. DNA fragments from selected regions of mitochondrial and ribosomal DNA were amplified by PCR and allelic forms identified following digestion with a panel of restriction enzymes, using DNA from a total of 115 individual worms from both people and pigs from 2 neighbouring villages. Significant frequency differences in both mtDNA haplotypes and the rDNA spacer were found between the 2 host-associated populations, indicating that they represented reproductively isolated populations. Mitochondrial haplotype frequencies were different from those observed in Guatemala and also from other Asian Ascaris populations, suggesting low levels of gene flow between populations. However, we found no evidence for significant heterogeneity in the genetic composition of Ascaris infrapopulations in either humans or pigs, possibly indicative of agricultural practices in China which have resulted in a random distribution of alleles within the parasite populations.

Transmission and natural regulation of infection with Ascaris lumbricoides in a rural community in China

A longitudinal study on a cohort of 215 people who remained untreated from June 1993 to June 1994 was carried out using fecal egg counts to examine the course of transmission and aspects of the natural regulation of the infection with Ascaris lumbricoides. The results indicate that the parasite population remained relatively stable during the years since overall prevalence remained steady above 60%. About 40% of the people in the cohort retained their infection intensity status throughout the year, in terms of light, medium, and heavy infections. The regulation of infection in the population could be attributed to the tendency for the loss of worms from people with initial light infections and the movement to medium infection intensity status of people with both light and heavy infections. Compared with adults, children showed a stronger tendency of retaining initial medium infections but weaker tendencies for keeping initial light infections and clearing themselves of infection. Predisposition to light and medium infections was detected in people who had experienced an uninfected period of 4-12 mo before reinfection was established.

Effect of dehydroepiandrosterone on hypoxic pulmonary vasoconstriction: a Ca(2+)-activated K(+)-channel opener

In the present study, we investigated the effects of the naturally occurring hormone dehydroepiandrosterone (DHEA) on hypoxic pulmonary vasoconstriction (HPVC) in isolated ferret lungs and on K+ currents in isolated and cultured ferret pulmonary arterial smooth muscle cells (FPSMCs). Severe alveolar hypoxia (3% O2-5% CO2-92% N2) caused an initial increase in pulmonary arterial pressure (Ppa) that was followed by a reversal in pulmonary hypertension. Maintaining alveolar hypoxia caused a sustained secondary increase in Ppa. Pretreating the lungs with the K(+)-channel inhibitor tetraethylammonium (TEA) caused a small increase in baseline Ppa, potentiated HPVC, and prevented the reversal of HPVC during the sustained alveolar hypoxia. Treating the lungs with DHEA caused a near-complete reversal of HPVC in control lungs and in lungs that were pretreated with TEA. DHEA also reversed the KCl-induced increase in Ppa. In FPSMCs, DHEA caused an adenosine 3',5'-cyclic monophosphate- and guanosine 3',5'-cyclic monophosphate-independent increase in activity of the Ca(2+)-activated K+ (KCa) current. In a cell-attached configuration, DHEA caused a mean shift of -22 mV in the voltage-dependent activation of the KCa channel. We conclude that DHEA is a novel KCa-channel opener of the pulmonary vasculature.

[Clinical and experimental studies in treating infantile acute respiratory tract infection with feiyan chuansou oral liquid]

OBJECTIVE

To study the therapeutical mechanism of Feiyan Chuansou Oral Liquid (FCOL) in treating infantile acute respiratory trct infection.

METHODS

Clinical and experimental studies with FCOL in treating infantile acute respiratory tract infection.

RESULTS

The clinical result showed that the antitussive, expectorant, anti-asthmatic effect and resolution of dry and moist rale and wheezing of FCOL were significantly better in treatment group than those in the control group (P < 0.05). Animal experimental results also showed that antitussive, expectorant, anti-asthmatic effect of FCOL were significantly better than those of the control group (P < 0.05-0.001). Bacteriostatic test in vitro showed that FCOL could inhibit streptococcus pneumoniae, klebsiella pneumoniae, influenza bacilli and staphylococcus aureus. Antivirologic test showed that FCOL could inhibit completely the influenza A virus and respiratory syncytial virus.

CONCLUSION

FCOL is an effective preparation in treating infantile acute respiratory infection.

Synthetic Analysis for Extracting Information on Soil Salinity Using Remote Sensing and GIS: A Case Study of Yanggao Basin in China

/ This paper reports the experience of extracting information on the salinity of soil and offers a method of synthetic analysis. The experimental areas for analysis are located in Yanggao Basin, Shanxi Province, China. The types of soil are mainly meadow soil and salinized meadow soil. The method of synthetic analysis of salinity uses a geographic information system (GIS) as a tool, building a basic saltwater analysis model of saline soil and adjusting the result with expert experience after computer processing. The method of feature extraction has been used for remotely sensed data. An optimum combination of features has been determined and, after comparing several combinations in the Yanggao region, an improved result has been obtained after Kauth-Thomas (K-T) transformation. For precise quantitative analysis of the salinization, not only Thematic Mapper (TM) remote sensing data, but also two forms of non-remote-sensing data are needed: depth of groundwater and mineralization rate of groundwater according to the theory of genesis of soil. For the analysis of synthetic compounded multisources, a generalized Bayes classification is used after overlay, matching, and related coefficients have been determined. On the premise that various information sources are independent, global membership functions with probability are used to combine various pieces of information in order to apply them directly to the pixels and classifications of soil salinity. The experiment indicates that this analytical method is sound because of the increased speed of processing and its simplicity and improved precision of classification of salinity. Finally, it is necessary to examine and adjust the factors using expert intelligence. The experiment shows that synthetic analysis using the geographic information system can raise the precision of quantitative analysis of salinity, which has advantages for environmental monitoring and management.KEY WORDS: Salinity; Remote sensing; Thematic Mapper; Geographic information system; Classification

[Investigation on hepatitis G virus (HGV) infection among different populations in Shenzhen]

A reverse transcription polymerase chain reaction assay with nested primers (RT-nested PCR) deduced from the 5' untranslated region of HGV genome was established to detect HGV RNA. By using this assay, we tested the serum samples of 106 paid blood donors, 80 intravenous drug users and 168 cases with viral hepatitis in Shenzhen, China. The positive rates of HGV RNA were 8.5%, 46.3% and 7.7%, respectively. The positive rates of HGV RNA in 61 cases with chronic hepatitis B and 33 cases with chronic hepatitis C were 8.2% and 21.2%. Among the 33 cases with chronic hepatitis C, the positive rate of HGV RNA in 15 cases infected with HCV by blood or blood products was 40.0%, compared with 1.7% in 18 cases without exposure to blood or blood products (P<0.05). The results of this study suggest that HGV infection is common in paid blood donors; the intravenous drug user is the population at high risk for HGV infection; the patients with post-transfusion chronic hepatitis C are often supperinfected with HGV.

[The value of blood sedimentation test in early diagnosis of amniotic fluid embolism]

OBJECTIVE

To explore the value of peripheral blood sedimentation in early diagnosis of amniotic fluid embolism.

METHOD

The contents of amniotic fluid were detected with blood sedimentation test in 15 cases of amniotic fluid embolism and 100 cases of normal pregnant women.

RESULTS

The contents of amniotic fluid including particles of vernix caseasa, lanugo hair and epithelium cells were found in serum of amniotic fluid embolism cases but not found in cases of normal pregnant women.

CONCLUSION

It suggested that the blood sedimentation test would be valuable for early diagnosis of amniotic fluid embolism.

[Experimental study in vivo on implantation of autogenous tendon cells after combining culture with carbon fibers]

In order to investigate the possibility of repairing injuried tendon with living artificial tendon, after combining culture, subcultured autogenous tendon cells with carbon fibers were implanted into the calcaneous tendon of rabbits. In different stages, the synthesis of type I collagen and their relevant morphological changes were observed. The results showed as follows: after implantation, tendon cells continued proliferating. Four weeks after implantation, tendon cells were detached from the carbon fibers and proliferated and produced collagen among the carbon fibers. The collagen fibrils were linked with each other to formed a dense structure. In the linkage site, the collagen fibrils originated from the implants joined to that from the ruptured end of the tendon, which meaned that the implant was healed with the recipient tendon. Observed under scanning electronic microscope, the tendon cells were lined among the carbon fibers evenly and in order, the collagen fibrils joined each other and formed an network, the fibrils were lined parallel to the carbon fibers. Under transparent electron microscope, the nucleolus were clear and organelle were abundant.

Effect of chronic hypoxia on K+ channels: regulation in human pulmonary vascular smooth muscle cells

We investigated the effects of chronic hypoxia on the major outward K+ currents in early cultured human main pulmonary arterial smooth muscle cells (HPSMC). Unitary currents were measured from inside-out, outside-out, and cell-attached patches of HPSMC. Chronic hypoxia depolarized resting membrane potential (Em) and reduced the activity of a charybdotoxin (CTX)- and iberiotoxin-sensitive, Ca2+-dependent K+ channel (KCa). The 4-aminopyridine-sensitive and CTX-insensitive channel or the delayed rectifier K+ channel was unaffected by chronic hypoxia. Chronic hypoxia caused a +33- to +53-mV right shift in voltage-dependent activation of K(Ca) and a decrease in K(Ca) activity at all cytosolic Ca2+ concentrations ([Ca2+]i) in the range of 0.1-10 microM. Thus the hypoxia-induced decrease in K(Ca) activity was most likely due to a decrease in K(Ca) sensitivity to Em and [Ca2+]i. Chronic hypoxia reduced the ability of nitric oxide (NO.) and guanosine 3',5'-cyclic monophosphate (cGMP) to activate K(Ca). The cGMP-dependent protein kinase-induced activation of K(Ca) was also significantly inhibited by chronic hypoxia. In addition, inhibiting channel dephosphorylation with calyculin A caused significantly less increase in K(Ca) activity in membrane patches excised from chronically hypoxic HPSMC compared with normoxic controls. This suggests that the mechanism by which hypoxia modulates NO.-induced K(Ca) activation is by decreasing the NO./cGMP-mediated phosphorylation of the channel.

[Morphological observation of combined-culture of tendon cell or fibroblast of rabbit with artificial materials in vitro]

In order to investigate the compatibility and growth between the tendon cell or fibroblast of rabbit and artificial materials, the combined-culture of the two cells with the carbon fiber, terylene and chitin was observed respectively. Results showed as following: in vitro, the compatibility of carbon fiber with these two cells was well, cell-adhesion ability was good as well. Few cells grew on terylene. Chitin inhibited the growth of either cells. No matter the tendon cell or the fibroblast, the amount of cells adhering on the carbon fiber was far more than that on terylene or chitin. When the three materials were interlaced together, the collagen fibers produced by the cells were arranged in direction parallel to the carbon fibers. As the time elapsed, the cells on the carbon fiber distributed evenly and enveloped the material in network-like fashion, this suggested that carbon fiber was a good material for producing living artificial tendon and ligament.

[The cloning and sequence analysis of cDNA of the partial E genomic region of Dengue type 4 virus from a Chinese patient]

The partial envelope (E) protein gene of Dengue virus type 4 (DV4), derived from the serum of a patient with dengue fever in an epidemic during October 1993 in Guangdong Province of China, was cloned and sequenced. DV RNA was converted to cDNA by reverse transcription with random primers before the polymerase chain reaction using DV4 specific primers was performed. The amplified product of 421bp was subsequently filled in 3' recessed ends, isolated, purified and inserted into pUC18 and pUC19 plasmid vector. Their sequences were determined by dideoxy nucleotide chain termination method. A comparison between DV4 Chinese strain and several other previously reported strains shows the homology to be 93.72% for the same dengue serotype, 61.26-64.40% for the other dengue serotypes, only 40.31% for Japanese encephalitis virus, which belongs to the member of flavivirus family. A conserved sequence with 12 amino acids observed from deduced protein sequence probably represents an essential functional element among flavivirus family.

[Experimental study on biological characteristics of tenocyte and fibroblast in rabbit]

In order to study the biological characteristics of tenocyte and fibroblast, the former was obtained from rabbit's tendon, and the latter from rabbits's skin. Both cells were cultured according Heuderson's method. The cell morphology, strapping and expanding time, and the type of collagen fiber synthesized in culture were observed. The results showed that the strapping and expanding time of fibroblast was faster than that of tenocyte. The cellular arrangement of fibroblast was irregular, but that in tenocyte was regular. Type I and III collagen of fibers were found in cultured fibroblost while only type I collagen fibers were found in culture of tenocyte. The tenocyte and fibroblast could be identified individually by strapping and expanding time, arrangement of cells and type of collagen fiber synthesized.

[Content determination of total coumarin of qian-hu]

The total content of coumarin in Qian-Hu was determined by UV spectrometry. The 25 samples which derived from different places of production were included eleven varieties. The results were found to have max = 322 nm, 99.18% of recovery rate and 2.08% of RSD.

Ascaris, people and pigs in a rural community of Jiangxi Province, China

A longitudinal investigation on natural populations of Ascaris in humans and pigs and an investigation of soil contamination with Ascaris eggs were carried out from June 1993 to June 1994 in 2 villages, Manhu area, Xinjian County, Jiangxi Province, China. Results from these studies indicate that although human ascariasis is endemic there is significant fluctuation in both prevalence and the mean number of eggs/g faeces (epg) of the communities. Fluctuation of age-stratified prevalence and mean epg was detected in children but not in most adult groups. Most cases of human ascariasis were judged to involve low intensities of infection and a typical overdispersion distribution pattern was observed through the year. It was estimated that during the year, nearly half of the eggs discharged in the environment came from infections in children aged between 2 and 15 years which accounted for about 30% of the total population. Soil in and around houses and in vegetable gardens was found to be contaminated by Ascaris eggs and this situation remained relatively stable throughout the year. Monthly developmental rate of Ascaris eggs in soil was detected and the results suggest that the fluctuation in prevalence observed during the year should be directly attributed to the effect of seasonality of egg development. Features of Ascaris infection in pigs were found to be similar to those in humans except for a lower mean intensity of infection. The possibility of cross-infection of Ascaris between human and pig hosts is discussed.

Mutations in active-site residues of the uracil-DNA glycosylase encoded by vaccinia virus are incompatible with virus viability

The D4R gene of vaccinia virus encodes a functional uracil-DNA glycosylase that is essential for viral viability (D. T. Stuart, C. Upton, M. A. Higman, E. G. Niles, and G. McFadden, J. Virol. 67:2503-2513, 1993), and a D4R mutant, ts4149, confers a conditional lethal defect in viral DNA replication (A. K. Millns, M. S. Carpenter, and A. M. DeLange, Virology 198:504-513, 1994). The mutant ts4149 protein was expressed in vitro and assayed for uracil-DNA glycosylase activity. Less than 6% of wild-type activity was observed at permissive temperatures, but the ts4149 protein was completely inactive at the nonpermissive temperature. Mutagenesis of the ts4149 gene back to wild type (Arg-179-->Gly) restored full activity. The ts4149 protein was considerably reduced in lysates of cells infected at the permissive temperature, and its activity was undetectable, even in the presence of the uracil glycosylase inhibitor protein, which inhibits the host uracil-DNA glycosylases but not that of vaccinia virus. Thus the ts4149 protein is thermolabile, correlating uracil removal with vaccinia virus DNA replication. Three active-site amino acids of the vaccinia virus uracil-DNA glycosylase were mutated (Asp-68-->Asn, Asn-120-->Val, and His-181-->Leu), producing proteins that were completely defective in uracil excision but still retained the ability to bind DNA. Each mutated D4R gene was transfected into vaccinia virus ts4149-infected cells in order to assess the recombination events that allowed virus survival at 40 degrees C. Genetic analysis and sequencing studies revealed that the only viruses to survive were those in which recombination eliminated the mutant locus. We conclude that the uracil cleavage activity of the D4R protein is essential for its function in vaccinia virus DNA replication, suggesting that the removal of uracil residues plays an obligatory role.

Ligustrazine-induced endothelium-dependent relaxation in pulmonary arteries via an NO-mediated and exogenous L-arginine-dependent mechanism

1. Ligustrazine (tetramethylpyrazine, TMP) is a vasodilator that has been reported to have pulmonary selective properties in vivo, but not in vitro. Although TMP is generally described as being endothelium-independent, we provide evidence here that TMP may have an endothelium-dependent and nitric oxide (NO)-mediated mechanism in pulmonary arteries that could predominate at concentrations used therapeutically in China. 2. The study was performed on isolated pulmonary (1-2 mm i.d.), intrapulmonary (200-850 microns) and mesenteric (200-400 microns) arteries of the rat using a Mulvaney-Halpen small vessel myograph, following preconstriction with phenylephrine (PE, 10 microM), prostaglandin F2 alpha (PGF2 alpha, 100 microM), or 75 mM K+ (KPSS, equimolar substitution for Na+). Values are shown as mean +/- s.e.mean, or for EC50S as mean [+/-95% confidence limits]. 3. TMP caused a concentration-dependent relaxation against all three agonists in both large (1.56 +/- 0.04 mm) and small (399 +/- 20 microM) pulmonary arteries; it was more potent in small compared to large arteries constricted with PE or PGF2 alpha (P < 0.05), but not those constricted with KPSS. The NO synthase (NOS) inhibitor, NG-monomethyl-L-arginine (L-NMMA, 100 microM) caused a significant shift to the right of these relationships, such that the EC50 for TMP in large pulmonary arteries constricted with PE increased from 522 [+130, -104] microM (n = 12) to 1828 [+395, -325] microM (n = 6, P < 0.01). Both removal of the endothelium and methylene blue (10 microM) had similar effects. 4. L-Arginine substantially reduced the EC50 for TMP in pulmonary arteries; in the presence of 400 microM L-arginine the EC50 for TMP in large arteries constricted with PE was 14.7 [+21.0, -8.6] microM, (n = 6, P < 0.001), and with 10 microM L-arginine 96.7 [+45.1, -30.7] microM, (n = 6, P < 0.001). Similar effects were seen in small arteries. L-Arginine had no effect in the absence of an endothelium. D-Arginine was ineffective, and inhibition of L-arginine uptake with L-lysine blocked the action of L-arginine. L-Arginine (400 microM) had no significant effect on TMP-induced relaxation in mesenteric arteries (n = 5). 5. L-Arginine itself caused a concentration-dependent relaxation in intrapulmonary arteries (639 +/- 34 microM) constricted with PE, reaching a maximum relaxation around 100-400 microM (42.4 +/- 3.0%, n = 16), but this was independent of the endothelium. TMP (10 and 100 microM) significantly enhanced the relaxation to L-arginine, with a maximum relaxation in the presence of 100 microM TMP of 81.7 +/- 6.2% (n = 5, P < 0.01), but the effect of TMP was entirely dependent on the endothelium. A similar effect was observed in PGF2 alpha-constricted pulmonary arteries. 6. These results show that TMP stimulates NO production at low concentrations in pulmonary arteries, via an apparently novel endothelium-resident mechanism that is dependent on exogenous L-arginine. Normal plasma L-arginine levels of around 150 microM would allow this mechanism to be maximally activated. As mesenteric arteries do not seem to express the mechanism to any significant extent, at low concentrations TMP would be effectively selective to the pulmonary vasculature, and may thus have potential as a therapeutic agent in pulmonary vascular disease.