RESUMEN
OBJECTIVE: FTY720 is a sphingosine 1-phosphate (S1P) receptor modulator that showed efficacy in phase II and III clinical trials in patients with multiple sclerosis (MS). FTY720 inhibits lymphocyte egress from secondary lymphoid organs into the peripheral circulation, thereby reducing the number of circulating naïve and central memory T cells, but not effector memory T cells in blood. Little is known to which of these memory T-cell subsets interleukin 17 (IL-17)-producing T cells (Th17 cells) belong, which are considered to be key mediators of inflammation in MS, and how they are affected by treatment with FTY720. In this study, we determined the phenotype and frequency of Th17 cells in blood of untreated, FTY720-treated, and interferon-beta (IFNbeta)-treated patients with MS and healthy donors. METHODS: In a prospective observational study, circulating T cells were phenotypically characterized and Th17 cells enumerated in T-cell subsets ex vivo. Production of IL-17 upon activation and expression of the Th17-specific transcription factor RORC2 was assessed in vitro. RESULTS: Th17 cells were found primarily within central memory T cells in all study populations. FTY720 treatment reduced blood central memory T cells, including RORC2+ and IL-17-producing T cells, by >90%. FTY720 did not per se affect IL-17 production when added to activated T cells in vitro. CONCLUSION: Phenotypic Th17 cells are defined by a central memory T-cell phenotype. FTY720 reduces these Th17 cells in blood. This is presumably because central memory T cells are retained by FTY720 in secondary lymphoid organs.
Asunto(s)
Memoria Inmunológica/efectos de los fármacos , Inmunosupresores/uso terapéutico , Esclerosis Múltiple/tratamiento farmacológico , Esclerosis Múltiple/inmunología , Glicoles de Propileno/uso terapéutico , Esfingosina/análogos & derivados , Linfocitos T/efectos de los fármacos , Adulto , Complejo CD3/metabolismo , Antígenos CD4/metabolismo , Estudios de Casos y Controles , Ensayos Clínicos Fase II como Asunto , Ensayos Clínicos Fase III como Asunto , Relación Dosis-Respuesta a Droga , Femenino , Clorhidrato de Fingolimod , Humanos , Factores Inmunológicos/uso terapéutico , Inmunosupresores/administración & dosificación , Interferón beta/uso terapéutico , Interleucina-17/metabolismo , Masculino , Esclerosis Múltiple/sangre , Glicoles de Propileno/administración & dosificación , Estudios Prospectivos , Receptores CCR4/metabolismo , Receptores CCR6/metabolismo , Esfingosina/administración & dosificación , Esfingosina/uso terapéutico , Linfocitos T/metabolismoRESUMEN
Definition of acute renal allograft rejection (AR) markers remains clinically relevant. Features of T-cell-mediated AR are tubulointerstitial and vascular inflammation associated with excessive extracellular matrix (ECM) remodeling, regulated by metzincins, including matrix metalloproteases (MMP). Our study focused on expression of metzincins (METS), and metzincins and related genes (MARGS) in renal allograft biopsies using four independent microarray data sets. Our own cases included normal histology (N, n = 20), borderline changes (BL, n = 4), AR (n = 10) and AR + IF/TA (n = 7). MARGS enriched in all data sets were further examined on mRNA and/or protein level in additional patients. METS and MARGS differentiated AR from BL, AR + IF/TA and N in a principal component analysis. Their expression changes correlated to Banff t- and i-scores. Two AR classifiers, based on METS (including MMP7, TIMP1), or on MARGS were established in our own and validated in the three additional data sets. Thirteen MARGS were significantly enriched in AR patients of all data sets comprising MMP7, -9, TIMP1, -2, thrombospondin2 (THBS2) and fibrillin1. RT-PCR using microdissected glomeruli/tubuli confirmed MMP7, -9 and THBS2 microarray results; immunohistochemistry showed augmentation of MMP2, -9 and TIMP1 in AR. TIMP1 and THBS2 were enriched in AR patient serum. Therefore, differentially expressed METS and MARGS especially TIMP1, MMP7/-9 represent potential molecular AR markers.
Asunto(s)
Trasplante de Riñón/patología , Riñón/patología , Adulto , Biomarcadores , Matriz Extracelular/patología , Femenino , Genes , Rechazo de Injerto/metabolismo , Rechazo de Injerto/patología , Humanos , Inmunohistoquímica , Masculino , Metaloproteinasa 2 de la Matriz , Metaloproteinasa 7 de la Matriz , Persona de Mediana Edad , ARN Mensajero , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
Metzincins, such as matrix metalloproteases (MMP), and extracellular matrix (ECM) proteins are differentially regulated in inflammation. We hypothesised that metzincins are also dysregulated in experimental acute cardiac allograft rejection. We investigated the Dark Agouti-to-Lewis (DA-to-Lew) rat model of acute cardiac allograft rejection. Cyclosporine (CsA) (7.5 mg/kg/d) was given from transplantation to sacrifice (day +5). At that time, mRNA levels were analysed by Affymetrix genechip and quantitative reverse transcription polymerase chain reaction (qRTPCR). MMP protein and activities were analysed by immunohistology, fluorometry, zymography and Western blots. In untreated rejected DA allografts, mRNA levels of MMP-2/-7/-9/-/12-/14, a disintegrin and metalloprotease (ADAM)-17, tissue inhibitor of metalloprotease (TIMP)-1/-3 were increased, whereas MMP-11/-16/-24 and TIMP-2/-4 were lowered compared to native DA hearts. With respect to these untreated allografts, CsA lowered mRNA levels of MMP-7, TIMP-1/-3 (TIMP-2/-4 remained relatively low) and ADAM17, but augmented mRNA levels of MMP-11/-16/-23 and of many ECM genes. Immunohistology showed increased staining of MMP-2 in acute rejection (AR). Overall MMP activity was augmented in both transplanted groups, but CsA reduced MMP-9 activity and MMP-14 production. Taken together, MMP and TIMP were upregulated during acute AR. CsA ameliorated histology of rejection but showed potential pro-fibrotic effects. Thus, MMP and TIMP may play a role in acute cardiac allograft rejection, and beneficial modification of the MMP-ECM balance requires interventions beyond CsA.
Asunto(s)
Ciclosporina/administración & dosificación , Rechazo de Injerto/metabolismo , Trasplante de Corazón/fisiología , Metaloproteinasas de la Matriz/metabolismo , Inhibidores Tisulares de Metaloproteinasas/metabolismo , Animales , Matriz Extracelular/metabolismo , Perfilación de la Expresión Génica , Trasplante de Corazón/inmunología , Modelos Animales , ARN Mensajero/análisis , Ratas , Ratas Endogámicas Lew , Ratas Endogámicas , Trasplante Homólogo , Regulación hacia Arriba/fisiologíaRESUMEN
Chronic renal allograft injury is often reflected by interstitial fibrosis (IF) and tubular atrophy (TA) without evidence of specific etiology. In most instances, IF/TA remains an irreversible disorder, representing a major cause of long-term allograft loss. As members of the protease family metzincins and functionally related genes are involved in fibrotic and sclerotic processes of the extracellular matrix (ECM), we hypothesized their deregulation in IF/TA. Gene expression and protein level analyses using allograft biopsies with and without Banff'05 classified IF/TA illustrated their deregulation. Expression profiles of these genes differentiated IF/TA from Banff'05 classified Normal biopsies in three independent microarray studies and demonstrated histological progression of IF/TA I to III. Significant upregulation of matrix metalloprotease-7 (MMP-7) and thrombospondin-2 (THBS-2) in IF/TA biopsies and sera was revealed in two independent patient sets. Furthermore, elevated THBS-2, osteopontin (SPP1) and beta-catenin may play regulatory roles on MMP. Our findings further suggest that deregulated ECM remodeling and possibly epithelial to mesenchymal transition (EMT) are implicated in IF/TA of kidney transplants, and that metzincins and related genes play an important role in these processes. Profiling of these genes may be used to complement IF/TA diagnosis and to disclose IF/TA progression in kidney transplant recipients.
Asunto(s)
Regulación de la Expresión Génica/genética , Trasplante de Riñón , Adulto , Atrofia/genética , Femenino , Fibrosis/genética , Perfilación de la Expresión Génica , Humanos , Inmunohistoquímica , Enfermedades Renales/genética , Enfermedades Renales/metabolismo , Enfermedades Renales/fisiopatología , Enfermedades Renales/cirugía , Trasplante de Riñón/clasificación , Masculino , Metaloproteinasa 7 de la Matriz/genética , Metaloproteinasa 7 de la Matriz/metabolismo , Persona de Mediana Edad , ARN Mensajero/genética , Trombospondinas/genética , Trasplante HomólogoRESUMEN
Improvements in our understanding of the anatomy of haemorrhoids have prompted the development of new and innovative methods of treatment. Conservative treatment consists of dietary and lifestyle modifications. Standard interventional procedures in outpatient treatment are injection sclerotherapy and rubber band ligation. Among the surgical options for prolapsed haemorrhoids, formal haemorrhoidectomy now competes with stapled haemorrhoidopexy, which is less painful and allows shorter convalescence but may have a higher recurrence rate and needs further long-term evaluation.
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Dietoterapia/métodos , Procedimientos Quirúrgicos del Sistema Digestivo/métodos , Hemorroides/terapia , Conducta de Reducción del Riesgo , Grapado Quirúrgico/métodos , Alemania , Humanos , Guías de Práctica Clínica como Asunto , Pautas de la Práctica en Medicina , Grapado Quirúrgico/instrumentaciónRESUMEN
Chronic renal allograft rejection is characterized by alterations in the extracellular matrix compartment and in the proliferation of various cell types. These features are controlled, in part by the metzincin superfamily of metallo-endopeptidases, including matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase (ADAM) and meprin. Therefore, we investigated the regulation of metzincins in the established Fisher to Lewis rat kidney transplant model. Studies were performed using frozen homogenates and paraffin sections of rat kidneys at day 0 (healthy controls) and during periods of chronic rejection at day +60 and day +100 following transplantation. The messenger RNA (mRNA) expression was examined by Affymetrix Rat Expression Array 230A GeneChip and by real-time Taqman polymerase chain reaction analyses. Protein expression was studied by zymography, Western blot analyses, and immunohistology. mRNA levels of MMPs (MMP-2/-11/-12/-14), of their inhibitors (tissue inhibitors of metalloproteinase (TIMP)-1/-2), ADAM-17 and transforming growth factor (TGF)-beta1 significantly increased during chronic renal allograft rejection. MMP-2 activity and immunohistological staining were augmented accordingly. The most important mRNA elevation was observed in the case of MMP-12. As expected, Western blot analyses also demonstrated increased production of MMP-12, MMP-14, and TIMP-2 (in the latter two cases as individual proteins and as complexes). In contrast, mRNA levels of MMP-9/-24 and meprin alpha/beta had decreased. Accordingly, MMP-9 protein levels and meprin alpha/beta synthesis and activity were downregulated significantly. Members of metzincin families (MMP, ADAM, and meprin) and of TIMPs are differentially regulated in chronic renal allograft rejection. Thus, an altered pattern of metzincins may represent novel diagnostic markers and possibly may provide novel targets for future therapeutic interventions.
Asunto(s)
Regulación de la Expresión Génica , Rechazo de Injerto , Trasplante de Riñón , Metaloproteinasas de la Matriz/genética , Metaloendopeptidasas/genética , Proteínas ADAM/genética , Proteína ADAM17 , Animales , Biomarcadores , Enfermedad Crónica , Rechazo de Injerto/diagnóstico , Rechazo de Injerto/terapia , Masculino , Metaloproteinasa 2 de la Matriz/genética , Metaloproteinasa 9 de la Matriz/genética , Análisis de Secuencia por Matrices de Oligonucleótidos , Ratas , Ratas Endogámicas F344 , Ratas Endogámicas Lew , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Inhibidor Tisular de Metaloproteinasa-2/genética , Factor de Crecimiento Transformador beta/genética , Factor de Crecimiento Transformador beta1 , Trasplante HomólogoRESUMEN
The anatomical structures of the rectum and anus are a functional unit designed to maintain continence mechanism. A pure anatomical description often fails to delineate this critical functional interaction. The topographic anatomy of the anorectum must be combined with an understanding of the mechanisms of anal continence and defecation, which can be transferred to clinical and especially surgical practice. The feedback-controlled reflex system of continence must be understood; it hinges on a complex interaction between the somatic and autonomic nervous systems.
Asunto(s)
Canal Anal/fisiopatología , Recto/fisiopatología , Canal Anal/patología , Defecación/fisiología , Incontinencia Fecal/diagnóstico , Incontinencia Fecal/patología , Incontinencia Fecal/fisiopatología , Hemorroides/diagnóstico , Hemorroides/patología , Hemorroides/fisiopatología , Humanos , Tono Muscular/fisiología , Músculo Esquelético/patología , Músculo Esquelético/fisiopatología , Recto/patologíaRESUMEN
Management of patients with anorectal melanoma is still controversial. To reach a rationale therapeutic approach, we reviewed our experience obtained over the past decade. In all, 19 consecutive patients with the diagnosis of anorectal melanoma were included in this retrospective survey. Details of the patients' presentation, symptoms, tumour size and histology and tumour state were recorded, and the primary therapeutic procedures were evaluated in detail. The size of the tumours ranged between 0.5 and 7 cm in diameter. The median tumour thickness was 10 mm (range 0.6-40 mm). At diagnosis, six of 19 patients already presented with either regional or distant metastases. The remaining 13 patients were treated with curative intend, either by abdomino-perineal resection (APR) or wide local excision (WLE). The form of operative therapy, however, had no impact on overall survival. Nevertheless, the incidence of local recurrences was lower after APR even for patients with less favourable tumours. In conclusion, WLE alone is not sufficient for local tumour control of thick anorectal melanoma.
Asunto(s)
Neoplasias del Ano/cirugía , Melanoma/cirugía , Neoplasias del Recto/cirugía , Neoplasias del Ano/patología , Humanos , Masculino , Melanoma/patología , Melanoma/secundario , Persona de Mediana Edad , Metástasis de la Neoplasia , Recurrencia Local de Neoplasia , Neoplasias del Recto/patología , Análisis de SupervivenciaRESUMEN
Gene expression analysis using high-density cDNA or oligonucleotide arrays is a rapidly emerging tool for transcriptomics, the analysis of the transcriptional state of a cell or organ. One of the limitations of current methodologies is the requirement of a relatively large amount of total or polyadenylated RNA as starting material. Standard array hybridization protocols require 5-15 micrograms labeled RNA. To obtain these quantities from small amounts of starting RNA material, RNA can be amplified in a linear fashion. Here we introduce an optimized protocol for rapid and easy-to-use amplification of as little as 1 ng total RNA. Our analysis shows that this method is linear and highly reproducible and that it preserves similarities as well as dissimilarities between normal and disease-related samples. We applied this technique to the RNA expression profiling of human renal allograft biopsies with normal histology and compared them to the profiles of renal biopsies with histological evidence of chronic transplant nephropathy or chronic rejection. Among others, complement component C1r was found to be significantly up-regulated in chronic rejection and chronic transplant nephropathy biopsies compared to normal samples, while fructose-1,6-biphosphatase showed lower-than-normal expression.
Asunto(s)
Perfilación de la Expresión Génica/métodos , Riñón/patología , Técnicas de Amplificación de Ácido Nucleico/métodos , ARN/genética , Humanos , Riñón/metabolismo , Leucocitos Mononucleares/metabolismo , Control de Calidad , ARN/metabolismo , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
UNLABELLED: Stapler-haemorrhoidectomy causes theoretically a durable reposition of the prolapsed haemorrhoidal cushions and a reduction of the arterial inflow by clipping mucosa and submucosa. Until now, however, no exact data exist with respect to a potential reduction of the arterial inflow. METHODS: The question of a sufficient interruption of the end branches of the superior rectal artery should be answered with doppler ultrasound measurements before and after stapler-haemorrhoidectomy. RESULTS: The measurements were performed on 45 patients before and one month after stapler-haemorrhoidectomy. Preoperatively in all patients the three main branches of the artery at three, seven and eleven o'clock could be detected by doppler ultrasound. In 67 % of the patients a fourth, in 16 % a fifth and in 13 % a sixth vessel could be located. One month postoperatively in 80 % of the patients all main branches were further seen. In 16 % of the cases two main vessels, in 4 % only one main vessel could be identified. There was no correlation between postoperative outcome and number of vessels detected postoperatively. CONCLUSION: It is concluded that the postoperative outcome after stapler-haemorrhoidectomy does not depend on the complete interruption of the arterial inflow of the haemorrhoids. The complete reposition of the haemorrhoidal prolapse and thereby the improvement of the venous reflux out of the haemorrhoidal cushions might be more important.
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Hemorroides/cirugía , Complicaciones Posoperatorias/diagnóstico por imagen , Recto/irrigación sanguínea , Engrapadoras Quirúrgicas , Ultrasonografía Doppler , Adulto , Anciano , Arterias/diagnóstico por imagen , Femenino , Hemorroides/diagnóstico por imagen , Humanos , Masculino , Persona de Mediana Edad , Prolapso Rectal/diagnóstico por imagen , Prolapso Rectal/cirugía , Valores de Referencia , Resultado del TratamientoAsunto(s)
Trasplante de Riñón/fisiología , Factor de Crecimiento Transformador beta/metabolismo , Adulto , Biomarcadores , Biopsia , Femenino , Expresión Génica , Humanos , Glomérulos Renales/patología , Trasplante de Riñón/patología , Masculino , Persona de Mediana Edad , ARN Mensajero/metabolismo , Factor de Crecimiento Transformador beta/genética , Trasplante HomólogoRESUMEN
Diagnostic and therapeutic options of the benign tumors in the anal region will be discussed. There is no systematic scheme for these tumors depending on the polymorph aspects and different matrices in the borderline between ecto- and entoderma. Because of the localisation either in perianal skin, fossa ischiorectalis or in the retrorectal space there is a need of different therapeutic options and approaches.
Asunto(s)
Neoplasias del Ano/cirugía , Lesiones Precancerosas/cirugía , Neoplasias del Recto/cirugía , Neoplasias Cutáneas/cirugía , Canal Anal/patología , Canal Anal/cirugía , Neoplasias del Ano/patología , Humanos , Lesiones Precancerosas/patología , Pronóstico , Neoplasias del Recto/patología , Recto/patología , Recto/cirugía , Neoplasias Cutáneas/patologíaRESUMEN
Octreotide is a long-acting somatostatin analog that has been shown to have various effects in diabetes. This study was performed to evaluate whether octreotide affects the vascular complications of diabetes mellitus. Albuminuria and serum thrombomodulin were used as markers of vascular and renal dysfunction. We studied the effect of octreotide in 27 patients with insulin-dependent diabetes mellitus (IDDM). They received 200 microg octreotide per day over a period of 6 months. As a marker of endothelial cell damage, we measured the serum thrombomodulin level. We also measured urinary albumin excretion, hemoglobin A1c (HbA1c), insulin-like growth factor-1 (IGF-1), and other parameters. IGF-1 decreased from 123 ng/mL before treatment to 114 ng/mL after 6 months of octreotide treatment (P = .009), while no significant change was observed in the unblinded control group (from 103 ng/mL to 102 ng/mL after 6 months of treatment). Urinary albumin excretion in patients with macroalbuminuria declined from 1,124 mg/L before octreotide treatment to 556 mg/L after 6 months of treatment (P < .05), whereas no change was observed in the control group. There was also a reduction of the plasma thrombomodulin level from 61.8 ng/mL to 46.1 ng/mL (P < .07) after 6 months of treatment. Furthermore, HbA1c decreased from 8.75% +/- 1.27% to 8.12% +/- 1.23% (P < .07) after octreotide treatment.
Asunto(s)
Diabetes Mellitus Tipo 1/tratamiento farmacológico , Diabetes Mellitus Tipo 1/fisiopatología , Angiopatías Diabéticas/fisiopatología , Endotelio Vascular/fisiopatología , Hormonas/uso terapéutico , Octreótido/uso terapéutico , Trombomodulina/sangre , Adulto , Anciano , Creatinina/sangre , Angiopatías Diabéticas/tratamiento farmacológico , Nefropatías Diabéticas/fisiopatología , Neuropatías Diabéticas/fisiopatología , Retinopatía Diabética/fisiopatología , Endotelio Vascular/efectos de los fármacos , Femenino , Hemoglobina Glucada/análisis , Humanos , Insulina/uso terapéutico , Factor I del Crecimiento Similar a la Insulina/análisis , Masculino , Persona de Mediana EdadAsunto(s)
Estreñimiento/etiología , Factores de Edad , Anciano , Anciano de 80 o más Años , Enfermedad Crónica , Femenino , Geriatría , Alemania , Humanos , Masculino , Sociedades MédicasRESUMEN
Somatostatin receptor-expressing tumours are potential targets for therapy with radiolabelled somatostatin analogues. We have synthesized a number of such analogues in the past and identified [DOTA-dPhe1, Tyr3]octreotide (SMT 487) as the most promising candidate molecule because of its advantageous properties in cellular and in vivo tumour models. In the current paper we describe the radiotherapeutic effect of yttrium-90 labelled SMT 487 in Lewis rats bearing the somatostatin receptor-positive rat pancreatic tumour CA 20948. SMT 487 binds with nanomolar affinity to both the human and the rat somatostatin receptor subtype 2 (sst2) (human sst2 IC50=0.9 nM, rat sst2 IC50=0.5 nM). In vivo, 90Y-SMT 487 distributed rapidly to the sst2 expressing CA 20948 rat pancreatic tumour, with a tumour-to-blood ratio of 49.15 at 24 h post injection. A single intravenous administration of 10 mCi/kg 90Y-SMT 487 resulted in a complete remission of the tumours in five out of seven CA 20948 tumour-bearing Lewis rats. No regrowth of the tumours occurred 8 months post injection. Control animals that were treated with 30 microg/kg of unlabelled SMT 487 had to be sacrificed 10 days post injection due to excessive growth or necrotic areas on the tumour surface. Upon re-inoculation of tumour cells into those rats that had shown complete remission, the tumours disappeared after 3-4 weeks of moderate growth without any further treatment. The present study shows for the first time the curative potential of 90Y-SMT 487-based radiotherapy for somatostatin receptor-expressing tumours. Clinical phase I studies with yttrium-labelled SMT 487 have started in September 1997.
Asunto(s)
Octreótido/análogos & derivados , Neoplasias Pancreáticas/radioterapia , Radiofármacos/uso terapéutico , Receptores de Somatostatina/metabolismo , Radioisótopos de Itrio/uso terapéutico , Animales , Humanos , Octreótido/uso terapéutico , Neoplasias Pancreáticas/metabolismo , Reacción en Cadena de la Polimerasa , Ratas , Ratas Endogámicas Lew , Distribución TisularAsunto(s)
Oclusión de Injerto Vascular/prevención & control , Hormonas/administración & dosificación , Octreótido/administración & dosificación , Túnica Media/patología , Enfermedades Vasculares/tratamiento farmacológico , Angioplastia/efectos adversos , Animales , Prótesis Vascular/efectos adversos , Arterias Carótidas/patología , División Celular/efectos de los fármacos , Movimiento Celular/efectos de los fármacos , Ratas , Túnica Media/efectos de los fármacos , Enfermedades Vasculares/patologíaRESUMEN
1. [125I]-[LTT]SRIF-28 and [125I]-SMS 201-995 were used to identify and characterize somatostatin (SRIF) receptors localized in rat lung tissue. In vitro autoradiography of rat lung tissue sections showed the existence of specific, high affinity binding sites for [125I]-[LTT]SRIF-28 without any significant specific binding of the sst2/sst5-receptor selective ligand [125I]-SMS 201-995. 2. In radioligand binding studies, specific binding of [125I]-[LTT]SRIF-28 to membranes of rat lung was linearly related to the concentration of membrane protein used with only a small portion of nonspecific binding. With [125I]-SMS 201-995 no specific binding could be observed up to a membrane concentration of 0.1 mg of protein/assay tube. 3. [125I]-[LTT]SRIF-28 bound rapidly to rat lung membranes with an apparent association rate constant (kapp) of 1.8 +/- 0.1 h-1 (n = 3). The equilibrium of specific binding was reached after an incubation period of approximately 90 min at room temperature and remained constant for the next 3 h. The association rate constant (k1) was calculated to be 3.7 x 10(10) M-1 h-1. The dissociation reaction followed first order kinetics with a dissociation rate constant (k-1) = 0.44 +/- 0.07 h-1 corresponding to a half-time of 95 +/- 15 min (n = 3). From these kinetic experiments an equilibrium dissociation constant (KD) for the binding of [125I]-[LTT]SRIF-28 was calculated to be 11.9 pM. 4. Saturation binding of [125I]-[LTT]SRIF-28 revealed an equilibrium dissociation constant (KD) of 50.1 pM (pKD = 10.3 +/- 0.1; n = 3) and a receptor density (Bmax) of 78 +/- 3 fmol mg-1 protein. A Hill coefficient not significantly different from 1 indicated saturable binding to a single class of high affinity binding sites. 5. Specific binding of [125I]-[LTT]SRIF-28 to rat lung membranes was inhibited by SRIF-14, SRIF-28 and different SRIF analogues. SRIF and different synthetic short chain SRIF analogues exhibited the following rank order of potency: SRIF-28 > SRIF-14 > CGP 23996 >> RC 160 > BIM 23014 > SMS 201- 995 > BIM 23056 > MK 678. 6. The binding affinities for SRIF and the various SRIF analogues determined using rat lung tissue were in close correlation to those obtained with Chinese hamster ovary (CHO) cells stably expressing sst, (r = 0.92) and sst4 (r = 0.95) receptors, respectively. 7. Reverse transcriptase--polymerase chain reaction (RT-PCR) showed the predominant expression of mRNA specific for sst4 receptors as well as some weak sst1 mRNA expression. 8. The findings suggest that sst4 receptor expression is the predominant form of the somatostatin receptors identified in rat lung tissue. In this study we demonstrated for the first time the existence of sst4 receptors in mammalian tissue.