Allergic sensitization to Storage Dust Mites: a prospective study of patients with respiratory allergy

Summary: Objectives. To describe the prevalence of allergic sensitization to Storage Dust Mites (SDM), access whether the place of living and occupational exposure were determinants for SDM sensitization and study association between Lepidoglyphus destructor and other SDM sensitization. Methods. Prospective analysis of patients evaluated for suspected allergic rhinitis and/or asthma that performed Skin Prick Tests (SPT) to SDM between January and December 2018 in our Department. Results. Two hundred consecutive patients were evaluated for rhinitis and/or asthma in our outpatient consultation: 123 (61.5%) presented positivity for at least one SDM, 68.3% were female and the mean age was 33.1 ± 12.12. Lepidoglyphus destructor (69.9%) was the most prevalent, followed by Tyrophagus putrescentiae (50.4%), Blomia tropicalis and Glycyphagus domesticus (48.8%) and Acarus siro (24.4%). Living in a rural place was not associated with a higher prevalence of sensitization to SDM, except for Acarus siro (p = 0.032), and working in a place with storage areas was not associated with sensitization to any of SDM. Sensitization to Lepidoglyphus destructor was associated with sensitization to Blomia tropicalis, Glycyphagus domesticus and Tyrophagus putrescentiae (p less than 0.005), but not with Acarus siro.Conclusions. Our study suggests that our population, independently of their occupational exposure and place of residency, are sensitized to SDM and that evaluation of sensitization to SDM should be considered as standard practice.

Portuguese recommendations for the prevention, diagnosis and management of primary osteoporosis - 2018 update.

BACKGROUND: Advances in osteoporosis (OP)case definition, treatment options, optimal therapy duration and pharmacoeconomic evidence in the national context motivated the Portuguese Society of Rheumatology (SPR) to update the Portuguese recommendations for the diagnosis and management of osteoporosis published in 2007. METHODS: SPR bone diseases' working group organized meetings involving 55 participants (rheumatologists, rheumatology fellows and one OP specialist nurse) to debate and develop the document. First, the working group selected 11 pertinent clinical questions for the diagnosis and management of osteoporosis in standard clinical practice. Then, each question was investigated through literature review and draft recommendations were built through consensus. When insufficient evidence was available, recommendations were based on experts' opinion and on good clinical practice. At two national meetings, the recommendations were discussed and updated. A draft of the recommendations full text was submitted to critical review among the working group and suggestions were incorporated. A final version was circulated among all Portuguese rheumatologists before publication and the level of agreement was anonymously assessed using an online survey. RESULTS: The 2018 SPR recommendations provide comprehensive guidance on osteoporosis prevention, diagnosis, fracture risk assessment, pharmacological treatment initiation, therapy options and duration of treatment, based on the best available evidence. They attained desirable agreement among Portuguese rheumatologists. As more evidence becomes available, periodic revisions will be performed. Target audience and patient population: The target audience for these guidelines includes all clinicians. The target patient population includes adult Portuguese people. Intended use: These recommendations provide general guidance for typical cases. They may not be appropriate in all situations - clinicians are encouraged to consider this information together with updated evidence and their best clinical judgment in individual cases.

[McGrath video laryngoscope used with a Frova intubating introducer for management of the difficult airway]. / Uso del videolaringoscopio de McGrath junto con la guía Frova en el manejo de la vía aérea difícil.

The McGrath video laryngoscope is a new airway management device. It is similar to the Macintosh laryngoscope but incorporates a blade at a 60 degrees angle and a camera that sends an image to a color display screen connected to the handle. The device, which requires use of an anti-fog substance and an introducer to guide the angled blade, has been reported to aid in the management of difficult airways. We present 3 cases of difficult oral-tracheal intubation managed with the McGrath video laryngoscope and a Frova intubating introducer. Advantages of this introducer are that it offers the possibility of administering oxygen or changing the size of the endotracheal tube if the first choice proves inappropriate. We discuss whether or not tests to predict difficult airways are applicable when the McGrath video laryngoscope is being used, given that it is not necessary to align the axes of the 3 airways. We conclude it may be useful to combine the McGrath video laryngoscope and the Frova introducer to manage difficult airways.

Uso del videolaringoscopio de McGrath junto con la guía Frova en el manejo de la vía aérea difícil / McGrath video laryngoscope used with a Frova intubating introducer for management of the difficult airway

El videolaringoscopio de McGrath es un nuevo dispositivopara el tratamiento de la vía aérea, se asemeja aun laringoscopio de Macintosh pero incorpora una palacon una angulación de 60º y un sistema óptico conectadoa una pantalla en color que va unida al mango del videolaringoscopio.Requiere de la utilización de una sustanciaantivaho y de una guía que permita vencer el ángulode la pala. En la literatura se ha descrito su uso enpacientes con criterios de dificultad en el manejo de lavía aérea. Presentamos tres casos de intubación orotraquealdifícil que fueron intubados con el videolaringoscopiode McGrath y un introductor de Frova para laintubación. La utilización de este tipo de guía aporta unaserie de ventajas como la posibilidad de administraciónde oxígeno a través de la misma o la posibilidad de cambiarel tamaño del tubo endotraqueal si no hemos elegidoel adecuado. Discutimos la idoneidad de las pruebaspredictoras de intubación orotraqueal difícil debido a lano necesidad de alineación de los tres ejes cuando se utilizael videolaringoscopio de McGrath. Concluimos quela combinación de videolaringoscopio de McGrath yguía Frova puede ser una buena opción para el manejode la vía aérea difícil(AU)

The McGrath video laryngoscope is a new airwaymanagement device. It is similar to the Macintoshlaryngoscope but incorporates a blade at a 60° angle anda camera that sends an image to a color display screenconnected to the handle. The device, which requires useof an anti-fog substance and an introducer to guide theangled blade, has been reported to aid in themanagement of difficult airways. We present 3 cases ofdifficult oral-tracheal intubation managed with theMcGrath video laryngoscope and a Frova intubatingintroducer. Advantages of this introducer are that itoffers the possibility of administering oxygen or changingthe size of the endotracheal tube if the first choice provesinappropriate. We discuss whether or not tests to predictdifficult airways are applicable when the McGrath videolaryngoscope is being used, given that it is not necessaryto align the axes of the 3 airways. We conclude it may beuseful to combine the McGrath video laryngoscope andthe Frova introducer to manage difficult airways(AU)

Role of activator protein-1 on the effect of arginine-glycine-aspartic acid containing peptides on transforming growth factor-beta1 promoter activity.

While arginine-glycine-aspartic acid-based peptidomimetics have been employed for the treatment of cardiovascular disorders and cancer, their use in other contexts remains to be explored. Arginine-glycine-aspartic acid-serine induces Transforming growth factor-beta1 transcription in human mesangial cells, but the molecular mechanisms involved have not been studied extensively. We explored whether this effect could be due to Activator protein-1 activation and studied the potential pathways involved. Addition of arginine-glycine-aspartic acid-serine promoted Activator protein-1 binding to its cognate sequence within the Transforming growth factor-beta1 promoter as well as c-jun and c-fos protein abundance. Moreover, this effect was suppressed by curcumin, a c-Jun N terminal kinase inhibitor, and was absent when the Activator protein-1 cis-regulatory element was deleted. Activator protein-1 binding was dependent on the activity of integrin linked kinase, as transfection with a dominant negative mutant suppressed both Activator protein-1 binding and c-jun and c-fos protein increment. Integrin linked kinase was, in turn, dependent on Phosphoinositol-3 kinase activity. Arginine-glycine-aspartic acid-serine stimulated Phosphoinositol-3 kinase activity, and Transforming growth factor-beta1 promoter activation was abrogated by the use of Phosphoinositol-3 kinase specific inhibitors. In summary, we propose that arginine-glycine-aspartic acid-serine activates Integrin linked kinase via the Phosphoinositol-3 kinase pathway and this leads to activation of c-jun and c-fos and increased Activator protein-1 binding and Transforming growth factor-beta1 promoter activity. These data may contribute to understand the molecular mechanisms involved in the cellular actions of arginine-glycine-aspartic acid-related peptides and enhance their relevance as these products evolve into clinical therapeutic use.

Collagen I upregulates extracellular matrix gene expression and secretion of TGF-beta 1 by cultured human mesangial cells.

Progressive renal diseases are characterized by an increased synthesis of extracellular matrix (ECM) components. The mechanisms involved in the development of these alterations are not completely known, but a crucial role for TGF-beta 1 has been suggested. Moreover, the ability of the ECM to modulate the phenotypic expression of different cell types has been widely described. In experiments presented here, human mesangial cells (HMC) were grown on collagen type I (COL I) or IV (COL IV). ECM protein and TGF-beta 1 mRNA expression were evaluated by Northern blot analysis, and TGF-beta 1 secretion was evaluated by ELISA. The involvement of tyrosine kinase and serine-threonine kinase pathways was studied by Western blot analysis, immunofluorescence, and in vitro kinase assays. HMC cultured on COL I showed an increased mRNA expression of COL I and COL IV, fibronectin, and TGF-beta 1. Both tyrosine phosphorylation and integrin-linked kinase (ILK) activity increased when HMC were cultured on COL I, and blockade of these pathways inhibited the increased secretion of TGF-beta 1. In conclusion, the present results support a role for extracellular COL I in the regulation of TGF-beta 1 synthesis during progressive renal sclerosis and fibrosis and the subsequent increase in newly synthesized ECM proteins. In addition, ILK, along with the tyrosine kinases, participates in the genesis of this effect.

Arg-Gly-Asp-Ser (RGDS) peptide stimulates transforming growth factor beta1 transcription and secretion through integrin activation.

Extracellular matrix (ECM) components, through specific peptide motifs such as Arg-Gly-Asp (RGD), interact with integrins and can modify the behavior of cells. Transforming growth factor-beta1 (TGF-beta1) is the main cytokine involved in the synthesis of ECM proteins. We analyzed the effect of a RGD-containing peptide, as Arg-Gly-Asp-Ser (RGDS), on the regulation of TGF-beta1 secretion in cultured human mesangial cells. We found that RGDS increased mRNA expression and secretion of TGF-beta1 by stimulating the TGF-beta1 gene promoter. This effect was dependent on the interaction of RGDS with integrins. We evaluated the signaling pathways implicated in TGF-beta1 production by analyzing the effect of RGDS on kinase-related integrins. RGDS stimulated tyrosine phosphorylation as well as integrin-linked kinase (ILK) activity. However, tyrosine kinase inhibitors did not prevent the RGDS effect. In contrast, the inhibition of ILK by cell transfection with a kinase dead-ILK completely abolished the increased TGF-beta1 secretion and promoter activity in the presence of RGDS. Thus RGDS modulates the secretion of TGF-beta1, probably through increased synthesis by interacting with integrins and activating ILK. This supports a role for ECM components in the regulation of their own secretion.

Angiotensin II induces a rapid and transient increase of reactive oxygen species.

Vascular smooth muscle cells (VSMC) exhibit a hypertrophic and contractile response after angiotensin II (Ang II) treatment, and the NADH/NADPH oxidase-dependent synthesis of hydrogen peroxide (H(2)O(2)) seems to play a central role in these responses. Present experiments were designed to analyze the mechanisms responsible for the rapid changes induced by Ang II in the intracellular H(2)O(2) concentration in VSMC. Ang II induced a quick and transient increase of dichlorodihydrofluorescein (DCHF) fluorescence in VSMC, an effect that was completely abolished by catalase and by diethyldithiocarbamate, a cell-permeable superoxide dismutase inhibitor. Losartan and pertussis toxin prevented the stimulatory effect of Ang II. Both diphenylene iodonium (NADH/NADPH oxidase blocker) and 3-(4-octadecylbenzoyl)acrylic acid (phospholipase A2 blocker) inhibited the changes in DCHF fluorescence induced by Ang II, in a dose-dependent fashion, and the effects of both inhibitors were additive. These data demonstrate that Ang II induces a very quick and transient increase of H(2)O(2) in VSMC. This effect depends on the receptor type 1, is linked to a G protein, and involves both NADH/NADPH oxidase and phospholipase A2 activation. The mechanism may be related to the previously proposed role of H(2)O(2) in the genesis of the Ang II-induced cell contraction.

Mechanisms of cGMP-dependent mesangial-cell relaxation: a role for myosin light-chain phosphatase activation.

Although the cGMP-dependent relaxation of contractile cells seems to depend on the ability of the cyclic nucleotide to interfere with intracellular calcium, this does not appear to be the only mechanism involved. The present experiments were designed to analyse alternative mechanisms, trying to test the hypothesis that cGMP could relax rat mesangial cells by activating myosin light-chain phosphatase (MLC-PP), with the subsequent dephosphorylation of myosin light chain (MLC). The effect of a cGMP analogue, dibutyryl cGMP (dbcGMP), on angiotensin II-(AII) and PMA-induced MLC phosphorylation (MLCP) was tested, in the presence of calyculin A (CA), an inhibitor of MLC-PP. MLCP was measured, after cell labelling with (32)P, by immunoprecipitation. dbcGMP prevented the increased MLCP induced by AII or PMA, and this inhibition was blocked by CA. dbcGMP also increased the MLC dephosphorylation observed in cells incubated with AII and in which MLC kinase and protein kinase C activities were blocked. The AII-elicited increased intracellular calcium concentration was only partially inhibited by dbcGMP. These results suggest that the cGMP-induced mesangial-cell relaxation could be due, at least partially, to the stimulation of MLC-PP.

Incidence, characterization and prognostic significance of chromosomal abnormalities in 640 patients with primary myelodysplastic syndromes. Grupo Cooperativo Español de Citogenética Hematológica.

Recently, a consensus International Prognostic Scoring System (IPSS) for predicting outcome and planning therapy in the myelodysplastic syndromes (MDS) has been developed. However, the intermediate-risk cytogenetic subgroup defined by the IPSS includes a miscellaneous number of different single abnormalities for which real prognosis at present is uncertain. The main aims of this study were to evaluate in an independent series the prognostic value of the IPSS and to identify chromosomal abnormalities with a previously unrecognized good or poor prognosis in 640 patients. In univariate analyses, cases with single 1q abnormalities experienced poor survival, whereas those with trisomy 8 had a higher risk of acute leukaemic transformation than the remaining patients (P = 0.004 and P = 0.009 respectively). Patients with single del(12p) had a similar survival to patients with a normal karyotype and showed some trend for a better survival than other cases belonging to the IPSS intermediate-risk cytogenetic subgroup (P = 0.045). Multivariate analyses demonstrated that IPSS cytogenetic prognostic subgroup, proportion of bone marrow blasts and haemoglobin level were the main prognostic factors for survival, and the first two characteristics and platelet count were the best predictors of acute leukaemic transformation risk. A large international co-operative study should be carried out to clarify these findings.

Mechanisms involved in the somatostatin-induced contraction of vascular smooth muscle cells.

In experimental models and in humans, somatostatin (SRIF) is able to contract certain vascular structures. The present experiments were designed to assess the capacity of SRIF to contract cultured rat aortic vascular smooth muscle cells (VSMC), and to analyze the possible mechanisms involved. Cells incubated with SRIF showed a significant reduction in planar cell surface area, in a time- and dose-dependent manner. This effect was partially blocked by preincubating the cells with a combination of calcium antagonists (10 microM verapamil, plus 10 microM 3,4,5-Trimethoxybenzoic acid 3-(diethylanino) octyl ester TMB)-8). SRIF was also able to stimulate myosin light-chain phosphorylation in VSMC. A small but significant increase of intracellular calcium concentration, and decreased levels of cAMP, without changes in cGMP, were detected in VSMC incubated with SRIF. A search for the known SRIF receptors present in these cells, by reverse transcription-polymerase chain reaction, only SRIF receptor-4 was found to be present. These results demonstrate the ability of SRIF to contract cultured rat VSMC. The contraction observed in these cells appears to be due to a mixed mechanism, that involves [Ca2+]i and cAMP as second messengers, and is likely mediated via SRIF receptor-4.

Co-metabolism and microbial growth in the biodegradation of alkylbenzenesulphonates.

Two organisms, CCMI507 and CCMI852, degrading undecylbenzenesulphonate (LAS) by the ortho- and meta-cleavage pathways were studied in cultures where glucose was used as carbon and energy source. CCMI507 (ortho-pathway) started the degradation of LAS at the beginning of the culture development in parallel with glucose utilization. The degradation followed a steady profile of degradation until 77% of LAS was degraded in the culture containing initially 5 mg l-1 of the compound and 81% in the cultures containing initially 10 and 20 mg l-1 of LAS, after 72 h fermentation. The organism CCMI852 (meta-pathway) started degrading the compound only after 20 h, when 75% of glucose was spent and well within the stationary-phase. After 72 h fermentation the level of degradation by CCMI852 varied from 70% (5 mg l-1 of LAS) to around 75% (10 and 20 mg l-1 of LAS).

Haemodialyser biocompatibility and erythrocyte structure and function.

There is controversy as to the clinical importance of providing haemodialysis (HD) with biocompatible versus non-biocompatible membranes. The effects of both acute and chronic dialysis with a biocompatible membrane (polyacrylonitrile, PAN) and a non-biocompatible membrane (cuprophane, CU) on the structural and functional properties of human erythrocytes have been examined. All 27 studied HD patients had increased erythrocyte osmotic fragility (OF) compared to controls; a single CU HD decreased mean OF (% lysis) by 13% without altering cell cholesterol. A single PAN HD decreased OF by a significantly greater amount (24%) and was associated with a 20% reduction in cell cholesterol. Chronic PAN HD for 6 months was associated with a sustained reduction in osmotic fragility compared to chronic CU HD (mean lysis 16% vs 45%) with no differences in mean pre-HD cell cholesterol. A single CU HD was associated with increased mean erythrocyte malonyldialdehyde (MDA) and reduced membrane content of spectrin and band 3 and this was significantly different from the effects of PAN. A single CU or PAN HD had no significant action on reduced glutathione (GSH), ankyrin, actin or sodium pump activity. Chronic HD was associated with increased GSH, and decreased ankyrin and band 3 protein compared with controls but the results for CU and PAN were not different. There was a non-significant tendency for higher MDA levels after chronic CU HD compared to PAN. These results indicate that the structural integrity of erythrocytes is improved by PAN HD with respect to CU but this difference cannot easily be ascribed to gross changes in structural proteins, ionic homeostasis or oxidation status.

[Cytogenetic alterations found by chromosome analysis and fish technique in two patients with variant chronic lymphocytic leukemia]. / Alteraciones citogenéticas encontradas por análisis cromosómico y técnica FISH en dos pacientes con variantes de leucemia linfática cronica.

Chromosomal studies in CLL have yielded poorer results than in other blood diseases because of the low mitotic index of the B cells. The FISH technique is a very useful tool for trisomy 12 detection in interphase nuclei in CLL, although this method cannot be a substitutive for conventional cytogenetics. The FISH technique was applied in two cases of CLL by means of satellite DNA probing specific for chromosome 12 according to the Oncor S 1370-CF kit protocol. Trisomy 12 was detected, along with other chromosomal abnormalities secondary to this trisomy. Both patients had lymphocyte counts lower than 5.0 x 10(9)/L and their peripheral blood immunophenotype showed 58% lymphocytes with lambda sIg of medium density, co-expressing CD5 and unable to form rosettes with mouse red-cells. Patient no. 1 was 46,XY/47,XY + 12/47,XY + 12,5q-, and patient no. 2 was 46,XX/47,XX + 12,14q-. The presence of secondary anomalies could explain the special clinico-haematological picture, characterised by low lymphocytosis and presence of irregular nuclei in mature lymphocytes, along with the lack of CD23 expression and rosette formation with mouse red-cells. FISH technique combined with chromosome analysis may prove a useful means for diagnosing and recognising variants or specific entities within low-grade lymphoproliferative syndromes.

Effects of somatostatin on cultured human mesangial cells.

The present experiments were devoted to analyzing the hypothesis that somatostatin (SS) could modulate glomerular filtration rate by interacting with mesangial cells. Studies were performed in cultured human mesangial cells, passages 3-5. Radioligand experiments demonstrated the presence in the cells of two kinds of receptors, with high (dissociation constant 14 pM. Number of sites: 426 fmol/mg) and low (dissociation constant 56 pM. Number of sites: 20, 111 fmol/mg) affinity. SS prevented in a dose-dependent manner the reduction in planar cell surface area induced by 100 nM Angiotensin II (AII). This effect was not inhibited by the blockade of the vasorelaxing prostaglandins (indomethacin, 10 microM), nitric oxide (L-N-methyl-arginine, 0.2 mM), adenylate cyclase (2,5'-dideoxyadenosine, 0.1 mM), or guanylate cyclase (Methylene blue, 30 microM; LY-83583, 10 microM), but it was potentiated by zaprinast, an inhibitor of the cyclic GMP (cGMP)-specific phosphodiesterase. SS also blocked the increase in myosin light chain phosphorylation induced by AII. SS increased cGMP synthesis by cultured human mesangial cells, an effect that seemed to be dependent on the stimulation of a particulate guanylate cyclase. Preincubation of the cells with pertussis toxin (0.5 microgram/ml) inhibited the effect of SS on the AII-dependent changes in planar cell surface area, as well as the SS-dependent cGMP stimulation. In summary, these results demonstrate the ability of SS to relax cultured human mesangial cells, thus supporting a role for this peptide in the regulation of the glomerular filtration rate. The SS-dependent mesangial cell relaxation may be due to changes in the intracellular concentrations of cGMP, as a consequence of the activation of a particulate guanylate cyclase.

A possible role for platelet-activating factor in the hydrogen peroxide-induced TXB2 and PGE2 glomerular synthesis.

Hydrogen peroxide stimulates both prostanoid and platelet-activating factor (PAF) biosynthesis in cultured rat mesangial cells and isolated rat glomeruli. The present experiments were designed to try to establish some relationship between prostanoid and PAF synthesis in these renal structures, in the presence of hydrogen peroxide. Cells and glomeruli were incubated with hydrogen peroxide under different experimental conditions, and thromboxane B2 (TXB2), the stable metabolite of thromboxane A2 (TXA2), and prostaglandin E2 (PGE2) concentrations were measured in the supernatants of the cells or glomeruli. Moreover, H2O2-dependent PAF synthesis was measured by high performance liquid chromatography (HPLC) ([3H]acetate incorporation) and radioimmunoassay. H2O2 induced increased TXB2 and PGE2 production in cultured rat mesangial cells and isolated rat glomeruli. This effect was blocked by incubation in the presence of a PAF-receptor antagonist, BN-52021. This antagonist has no intrinsic effect either in basal prostanoid synthesis or in arachidonic acid-stimulated glomerular TXB2 synthesis. Alprazolam, another PAF antagonist, nonchemically related to BN-52021, also completely blocked the H2O2-induced production of TXB2 by isolated rat glomeruli. Moreover, H2O2 was also able to induce an increased [3H]acetate incorporation into a fraction comigrating with a PAF standard in HPLC in isolated glomeruli, and this effect was dependent on the H2O2 concentration tested. Moreover, H2O2 was also able to induce an increased [3H]acetate incorporation and increased synthesis of radioimmunoassayable PAF in cultured mesangial cells. These results suggest that the increased synthesis of PGE2 and TXB2 induced by H2O2 could be dependent on platelet-activating factor production.

Thromboxane A2 and platelet-activating factor decrease in the platelet-mesangial cell interactions.

To analyze the metabolisms of platelet-activating factor (PAF) and Thromboxane A2 (TxA2) when platelets and mesangial cells (MC) interact, immunoreactive thromboxane B2 (TxB2) and PAF were measured after incubation of cultured rat MC with platelets (P) and with platelet supernatants (PS). In both cases, TxB2 significantly decreased with respect to the P synthesis and to the PS content, suggesting an increased degradation of this metabolite or even the existence of a specific effect of MC upon platelet TxB2. When immunoreactive PAF was measured, results were comparable to those observed for TxB2. Moreover, when intrinsic mesangial cell synthesis of PAF was assessed by analyzing the [3H]-acetate incorporation by prelabeled MC in the HPLC fraction coeluting with cold PAF standards, it was possible to demonstrate that P or PS did not modify PAF synthesis in these cells. In summary, present results support the existence of a specific effect of mesangial cells upon platelet TxA2 and PAF.

Somatostatin activates particulate guanylate cyclase in cultured rat mesangial cells.

Although the ability of somatostatin (ST) to relax cultured rat mesangial cells has recently been described, the intimate cellular mechanisms responsible for this effect have not been adequately clarified. The present experiments were designed to test the hypothesis that cyclic GMP (cGMP) could be involved in the genesis of this relaxation. ST increased cGMP synthesis by cultured rat mesangial cells, in basal conditions and in the presence of isobutylmethylxanthine or zaprinast. This effect was dose-dependent, with a threshold value of about 1 nM and a maximal response at ST concentrations between 0.1 and 1 microM. This increased cGMP synthesis was dependent on the stimulation by ST of a particulate guanylate cyclase, as the synthesis of cGMP by a particulate membrane fraction obtained from the cells increased in the presence of ST. When the cGMP-specific phosphodiesterase of mesangial cells was blocked with zaprinast, the ST-dependent relaxation, assessed both by morphological and biochemical criteria, significantly increased with respect to the experiments performed without zaprinast. These results support a role for cGMP in the ST-dependent relaxation of cultured rat mesangial cells. The increased cGMP synthesis appears to be the consequence of the activation of some form of particulate guanylate cyclase.