RESUMO
The effect of 40% partial food deprivation was studied on the immunohistochemically detectable amount of glial fibrillary acidic protein (GFAP) - the specific marker of astroglia - in the dorsal subnucleus of lateral septum (LS) of male, intact and ovariectomized (OVX) female rats. Animals were either fed ad libitum (control) or 40% food deprived for one week, then perfusion-fixed, their brains removed, and serial vibratome sections were processed for the immunocytochemical localization of GFAP. Computeraided densitometry was carried out on digital photographs.The results showed that ovariectomy alone did not exert any effect on the density of GFAPimmunoreactivity (GFAP-IR) as compared to the values detected in intact females. Food deprivation increased the density of GFAP in each experimental group. The difference was most pronounced in males, significant in females and much less in ovariectomized females. Parietal cortex chosen as reference area did not show any increase in the local GFAP-IR.It was previously shown that the dorsal subnucleus of the lateral septum reacts with plastic neurochemical changes to food deprivation. Our results prove that these changes affect not only neuronal but also glial elements.
Assuntos
Astrócitos/fisiologia , Privação de Alimentos/fisiologia , Núcleos Septais/fisiologia , Animais , Feminino , Proteína Glial Fibrilar Ácida/metabolismo , Masculino , Ovariectomia , Ratos , Ratos WistarAssuntos
Analgésicos não Narcóticos/farmacologia , Bloqueadores dos Canais de Cálcio/farmacologia , Ácidos Pentanoicos/farmacologia , Administração Oral , Analgésicos não Narcóticos/química , Animais , Bloqueadores dos Canais de Cálcio/química , Canais de Cálcio Tipo L/efeitos dos fármacos , Canais de Cálcio Tipo N/efeitos dos fármacos , Linhagem Celular , Injeções Intravenosas , Masculino , Camundongos , Camundongos Endogâmicos DBA , Medição da Dor , Ácidos Pentanoicos/química , RatosRESUMO
Several novel N-type voltage sensitive calcium channel blockers showed high affinity in the IMR32 assay and efficacy in the anti-writhing model. Herein, we describe the design, synthesis, SAR studies, biological data, physicochemical properties and pharmacokinetics of this 4-piperidinylaniline series.
Assuntos
Analgésicos não Narcóticos/farmacologia , Compostos de Anilina/farmacologia , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio Tipo N/efeitos dos fármacos , Animais , Bloqueadores dos Canais de Cálcio/síntese química , Camundongos , Relação Estrutura-AtividadeRESUMO
Our drug discovery efforts for N-type calcium channel blockers in the 4-piperidinylaniline series led to the discovery of an orally active analgesic agent 26.1-[4-Dimethylamino-benzyl)-piperidin-4-yl]-[4-(3,3-dimethyl-but yl)-phenyl]-(3-methyl-but-2-enyl)amine (26) showed high affinity to functionally block N-type calcium channels (IC50=0.7 microM in the IMR32 assay) and exhibited high efficacy in the anti-writhing analgesia test with mice (ED50=12 mg/kg by po and 4 mg/kg by iv). In this report, the rationale for the design, synthesis, biological evaluation, and pharmacokinetics of this series of blockers is described.
Assuntos
Analgésicos/química , Analgésicos/farmacologia , Compostos de Anilina/química , Compostos de Anilina/farmacologia , Bloqueadores dos Canais de Cálcio/química , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio Tipo N/efeitos dos fármacos , Piperidinas/química , Piperidinas/farmacologia , Administração Oral , Analgésicos/síntese química , Compostos de Anilina/síntese química , Animais , Bloqueadores dos Canais de Cálcio/administração & dosagem , Bloqueadores dos Canais de Cálcio/síntese química , Linhagem Celular , Espectroscopia de Ressonância Magnética , Masculino , Espectrometria de Massas , Camundongos , Estrutura Molecular , Piperidinas/síntese química , Ratos , Ratos WistarRESUMO
Exploration of the SAR around the leucine side chain in a series of N,N-dialkyldipeptidylamines with potent functional activity at N-type VSCC is presented. A novel analog is disclosed which possesses improved aqueous solubility, in vivo activity in an audiogenic seizure model, and reversible blockade in electrophysiological assays.
Assuntos
Alcanos/química , Bloqueadores dos Canais de Cálcio/química , Canais de Cálcio Tipo N/metabolismo , Leucina/química , Oligopeptídeos/química , Alcanos/síntese química , Alcanos/farmacologia , Bloqueadores dos Canais de Cálcio/síntese química , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio Tipo N/efeitos dos fármacos , Dipeptídeos/síntese química , Dipeptídeos/química , Dipeptídeos/farmacologia , Eletrofisiologia , Oligopeptídeos/síntese química , Oligopeptídeos/farmacologia , Solubilidade , Relação Estrutura-Atividade , ômega-Conotoxinas/síntese química , ômega-Conotoxinas/química , ômega-Conotoxinas/farmacologiaRESUMO
In this article, the rationale for the design, synthesis, and biological evaluation of a series of N-type voltage-sensitive calcium channel (VSCC) blockers is described. N-Type VSCC blockers, such as ziconotide, have shown utility in several models of stroke and pain. Modification of the previously reported lead, 1a, led to several 4-(4-benzyloxylphenyl)piperidine structures with potent in vitro and in vivo activities. In this series, the most interesting compound, (S)-2-amino-1-{4-[(4-benzyloxy-phenyl)-(3-methyl-but-2-enyl)-amino]-p iperidin-1-yl}-4-methyl-pentan-1-one (11), blocked N-type calcium channels (IC(50) = 0.67 microM in the IMR32 assay) and was efficacious in the audiogenic DBA/2 seizure mouse model (ED(50) = 6 mg/kg, iv) as well as the antiwrithing model (ED(50) = 6 mg/kg, iv). Whole-cell voltage-clamp electrophysiology experiments demonstrated that compound 11 blocked N-type Ca(2+) channels and Na(+) channels in superior cervical ganglion neurons at similar concentrations. Compound 11, which showed superior in vivo efficacy, stands out as an interesting lead for further development of neurotherapeutic agents in this series.
Assuntos
Analgésicos não Narcóticos/síntese química , Anticonvulsivantes/síntese química , Bloqueadores dos Canais de Cálcio/síntese química , Neurônios/metabolismo , Piperidinas/síntese química , Estimulação Acústica , Analgésicos não Narcóticos/química , Analgésicos não Narcóticos/farmacocinética , Analgésicos não Narcóticos/farmacologia , Animais , Anticonvulsivantes/química , Anticonvulsivantes/farmacocinética , Anticonvulsivantes/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Bloqueadores dos Canais de Cálcio/química , Bloqueadores dos Canais de Cálcio/farmacocinética , Bloqueadores dos Canais de Cálcio/farmacologia , Linhagem Celular , Frequência Cardíaca/efeitos dos fármacos , Humanos , Técnicas In Vitro , Ativação do Canal Iônico , Masculino , Camundongos , Camundongos Endogâmicos DBA , Microssomos Hepáticos/metabolismo , Medição da Dor , Técnicas de Patch-Clamp , Piperidinas/química , Piperidinas/farmacocinética , Piperidinas/farmacologia , Ratos , Ratos Sprague-Dawley , Ratos Wistar , Convulsões/tratamento farmacológicoRESUMO
Voltage activated calcium channel (VACC) blockers have been demonstrated to have utility in the treatment of stroke and pain. A series of aminomethyl substituted phenol derivatives has been identified with good functional activity and selectivity for N-type VACC's over sodium and potassium channels. The methods of synthesis and preliminary pharmacology are discussed herein.
Assuntos
Bloqueadores dos Canais de Cálcio/síntese química , Bloqueadores dos Canais de Cálcio/farmacologia , Metano/análogos & derivados , Metano/farmacologia , Linhagem Celular , Metano/síntese química , Relação Estrutura-AtividadeRESUMO
Selective N-Type Voltage Sensitive Calcium Channel (VSCC) antagonists have shown utility in several models of pain and ischemia. We report the structure-activity relationship at the proximal phenyl group in a series of non-peptidyl VSCC blockers.
Assuntos
Compostos de Anilina/química , Compostos de Anilina/farmacologia , Bloqueadores dos Canais de Cálcio/química , Bloqueadores dos Canais de Cálcio/farmacologia , Leucina/análogos & derivados , Estimulação Acústica , Sequência de Aminoácidos , Compostos de Anilina/uso terapêutico , Animais , Bloqueadores dos Canais de Cálcio/uso terapêutico , Leucina/química , Leucina/farmacologia , Leucina/uso terapêutico , Camundongos , Camundongos Endogâmicos DBA , Dados de Sequência Molecular , Convulsões/tratamento farmacológico , Convulsões/fisiopatologia , Relação Estrutura-AtividadeRESUMO
Selective N-type voltage sensitive calcium channel (VSCC) blockers have shown efficacy in several animal models of stroke and pain. In the process of searching for small molecule N-type calcium channel blockers, we have identified a series of N-methyl-N-aralkyl-peptidylamines with potent functional activity at N-type VSCCs. The most active compound discovered in this series is PD 173212 (11, IC50 = 36 nM in the IMR-32 assays). SAR and pharmacological evaluation of this series are described.
Assuntos
Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio/metabolismo , Dipeptídeos/farmacologia , Animais , Bloqueadores dos Canais de Cálcio/uso terapêutico , Canais de Cálcio/efeitos dos fármacos , Dipeptídeos/química , Modelos Animais de Doenças , Humanos , Camundongos , Convulsões/tratamento farmacológico , Relação Estrutura-Atividade , Células Tumorais CultivadasRESUMO
Selective N-type Voltage Sensitive Calcium Channel (VSCC) blockers have shown utility in several models of stroke and pain. A series of N,N-dialkyldipeptidylamines with potent functional activity at N-type VSCC's has been identified. Multiple parallel synthesis of a focused array of thirty compounds using polymer-supported quenching reagents and preliminary pharmacology are presented. Eighteen compounds were identified with an IC50 below 1 microM in an in vitro functional assay.
Assuntos
Aminas/síntese química , Bloqueadores dos Canais de Cálcio/síntese química , Dipeptídeos/síntese química , Concentração Inibidora 50RESUMO
Selective N-type Voltage Activated Calcium Channel (VACC) blockers have shown utility in several models of stroke and pain. In the process of searching for small molecules as N-type calcium channel blockers, we have identified a series of N,N-dialkylpeptidylamines (e.g., PD 175069) with potent functional activity at N-type VACC. Further modification of the leucine moiety of PD 175069 with a cyclized ring structure provides a series of novel molecules. Syntheses and pharmacological evaluation of the series are presented.
Assuntos
Bloqueadores dos Canais de Cálcio/síntese química , Bloqueadores dos Canais de Cálcio/farmacocinética , Fenilalanina/análogos & derivados , Fenilalanina/síntese química , Fenilalanina/farmacocinética , Humanos , Concentração Inibidora 50 , Modelos Químicos , Células Tumorais CultivadasRESUMO
Selective N-type voltage sensitive calcium channel (VSCC) blockers have shown utility in several models of stroke and pain. We are especially interested in small molecule N-type calcium channel blockers for therapeutic use. Herein, we report a series of N,N-dialkyl-dipeptidylamines with potent functional activity at N-type VSCCs and in vivo efficacy. The synthesis, SAR, and pharmacological evaluation of this series are discussed.
Assuntos
Bloqueadores dos Canais de Cálcio/síntese química , Diaminas/síntese química , Diaminas/farmacologia , Dipeptídeos/síntese química , Dipeptídeos/farmacologia , Animais , Modelos Animais de Doenças , Camundongos , Camundongos Endogâmicos DBA , Modelos Químicos , Convulsões/tratamento farmacológicoRESUMO
We describe the first potent and selective blocker of the class E Ca2+channel. SNX-482, a novel 41 amino acid peptide present in the venom of the African tarantula, Hysterocrates gigas, was identified through its ability to inhibit human class E Ca2+ channels stably expressed in a mammalian cell line. An IC50 of 15-30 nM was obtained for block of the class E Ca2+ channel, using either patch clamp electrophysiology or K+-evoked Ca2+ flux. At low nanomolar concentrations, SNX-482 also blocked a native resistant or R-type Ca2+ current in rat neurohypophyseal nerve terminals, but concentrations of 200-500 nM had no effect on R-type Ca2+ currents in several types of rat central neurons. The peptide has the sequence GVDKAGCRYMFGGCSVNDDCCPRLGCHSLFSYCAWDLTFSD-OH and is homologous to the spider peptides grammatoxin S1A and hanatoxin, both peptides with very different ion channel blocking selectivities. No effect of SNX-482 was observed on the following ion channel activities: Na+ or K+ currents in several cultured cell types (up to 500 nM); K+ current through cloned potassium channels Kv1.1 and Kv1. 4 expressed in Xenopus oocytes (up to 140 nM); Ca2+ flux through L- and T-type Ca2+ channels in an anterior pituitary cell line (GH3, up to 500 nM); and Ba2+ current through class A Ca2+ channels expressed in Xenopus oocytes (up to 280 nM). A weak effect was noted on Ca2+ current through cloned and stably expressed class B Ca2+ channels (IC50 > 500 nM). The unique selectivity of SNX-482 suggests its usefulness in studying the diversity, function, and pharmacology of class E and/or R-type Ca2+ channels.
Assuntos
Bloqueadores dos Canais de Cálcio/química , Peptídeos/química , Venenos de Aranha/química , Sequência de Aminoácidos , Animais , Bloqueadores dos Canais de Cálcio/isolamento & purificação , Bloqueadores dos Canais de Cálcio/farmacologia , Canais de Cálcio/fisiologia , Linhagem Celular , Humanos , Masculino , Dados de Sequência Molecular , Oócitos/fisiologia , Técnicas de Patch-Clamp , Peptídeos/isolamento & purificação , Peptídeos/fisiologia , Bloqueadores dos Canais de Potássio , Ratos , Ratos Sprague-Dawley , Bloqueadores dos Canais de Sódio , Venenos de Aranha/isolamento & purificação , Venenos de Aranha/farmacologia , Transfecção , Células Tumorais Cultivadas , XenopusRESUMO
Voltage Activated Calcium Channel (VACC) blockers have been demonstrated to have utility in the treatment of pain and stroke. A series of aminomethyl substituted isoquinolinol derivatives with potent functional activity for N-type VACC's have been identified. Their synthesis and preliminary pharmacology are discussed herein.
Assuntos
Bloqueadores dos Canais de Cálcio/síntese química , Isoquinolinas/síntese química , Bloqueadores dos Canais de Cálcio/química , Humanos , Isoquinolinas/farmacologia , Modelos Químicos , Relação Estrutura-Atividade , Células Tumorais CultivadasRESUMO
The nail-patella syndrome is a hereditary disorder showing an autosomal dominant trait. It is characterized by a series of skeletal disorders and nephropathy. The skeletal defects and the renal involvement might occur separately. The usual clinical presenting syndromes of the nephropathy are asymptomatic proteinuria, microscopic haematuria and sometimes nephrotic syndrome. In a considerable proportion of patients renal failure develops. We summarise the clinico-pathological features of the disease presenting in two children and in a young man. The two children showed heavy microscopic occasionally, macroscopic haematuria, asymptomatic proteinuria and the adult patient had nephrotic syndrome. Nail-patella abnormalities were observed in one child without the involvement of family members. Except for the mother of the other child no urine abnormalities could be demonstrated in the patient's families. The kidney biopsy revealed the characteristic signs of the nail-patella syndrome in different extent: bundles of collagen fibrils in the glomerular basement membrane (GBM). Segmental and thinning of the GBM also occurred in the two children. This defect predisposes to the clinically dominant micro- and macroscopic haematuria. These children's reual function remained stable during the follow-up period of 4-7 years. In the GBM of the third patient small subepithelial electron dense deposits-corresponding to stage I. membranous glomerulonephritis- and extensive collagen deposition was found. After two years follow-up persistent nephrotic syndrome and gradual decline in renal function could be observed.
Assuntos
Síndrome da Unha-Patela , Adolescente , Adulto , Membrana Basal/ultraestrutura , Criança , Aberrações Cromossômicas/genética , Transtornos Cromossômicos , Feminino , Seguimentos , Humanos , Glomérulos Renais/ultraestrutura , Masculino , Microscopia Eletrônica , Síndrome da Unha-Patela/diagnóstico , Síndrome da Unha-Patela/genética , Síndrome da Unha-Patela/patologia , Síndrome Nefrótica/etiologia , Síndrome Nefrótica/patologiaRESUMO
Female BDF mice bearing estrogen-dependent MXT mouse mammary cancers were treated for 4 weeks with a cytotoxic analog of luteinizing hormone-releasing hormone (LH-RH). T-98 (agonist [D-Lys6]LH-RH linked to glutaryl-2(hydroxymethyl)anthraquinone). The effects of T-98 were compared to those of equimolar amounts of the cytotoxic moiety 2-(hydroxymethyl)anthraquinone hemiglutarate (G-HMAQ) and carrier LH-RH agonist [D-Lys6]LH-RH. Both T-98 and [D-Lys6]LH-RH significantly inhibited the growth of MXT cancers, but G-HMAQ had only a minor non-significant effect. Cytotoxic analog T-98 and the carrier [D-Lys6]LH-RH had similar inhibitory hormonal activities on the pituitary-gonadal axis, but T-98 caused a larger reduction in tumor volume and decreased proliferation characteristics such as mitotic activity and AgNOR numbers in tumor cells to a greater extent than the carrier. Tumor inhibition by T-98, [D-Lys6]LH-RH, and ovariectomy was connected with a significant decrease in binding capacity of EGF receptors in tumor cell membranes. The concentration of EGF receptors remained high in tumors that continued to enlarge in spite of treatment and in all control untreated tumors, even those of small size. Thus, the changes in EGF receptors are likely to be the result of the therapy. Treatment with T-98 caused a greater reduction in the binding capacity of EGF receptors in tumors than [D-Lys6]LH-RH. This could explain the higher inhibitory effect of the cytotoxic analog on tumor growth. Since radiolabeled T-98 was shown to accumulate in MXT cancers 3 hours after a subcutaneous injection, this indicates that specific targeting might play a role in the antitumor effect exerted by this cytotoxic analog.
Assuntos
Antraquinonas/farmacologia , Antineoplásicos Hormonais/farmacologia , Estrogênios/fisiologia , Hormônio Liberador de Gonadotropina/análogos & derivados , Neoplasias Mamárias Experimentais/tratamento farmacológico , Neoplasias Mamárias Experimentais/patologia , Neoplasias Hormônio-Dependentes/tratamento farmacológico , Neoplasias Hormônio-Dependentes/patologia , Animais , Antraquinonas/farmacocinética , Antineoplásicos Hormonais/farmacocinética , Divisão Celular/efeitos dos fármacos , Divisão Celular/fisiologia , Receptores ErbB/metabolismo , Estradiol/sangue , Feminino , Hormônio Liberador de Gonadotropina/farmacocinética , Hormônio Liberador de Gonadotropina/farmacologia , Radioisótopos do Iodo , Hormônio Luteinizante/sangue , Neoplasias Mamárias Experimentais/metabolismo , Camundongos , Camundongos Endogâmicos , Neoplasias Hormônio-Dependentes/metabolismo , Distribuição TecidualRESUMO
We report the case of a young alcoholic male whose first renal biopsy disclosed mesangiocapillary glomerulonephritis. One month later he took 1.5 g paracetamol to control the fever. Soon he got hospitalized due to toxicoderma, elevated liver and renal function tests. While the liver enzymes returned to normal, uremia developed. A repeated renal biopsy revealed severe interstitial inflammation, tubular atrophy. Haemodialysis was started and he got steroids (1 mg/kg body weight). He showed considerable recovery of renal function in some weeks. The case points to the possibility that paracetamol-even in therapeutic dosage-might result in hepatic and renal damage in alcoholics.
Assuntos
Acetaminofen/toxicidade , Anti-Inflamatórios não Esteroides/toxicidade , Glomerulonefrite Membranoproliferativa/induzido quimicamente , Nefrite Intersticial/induzido quimicamente , Adulto , Alcoolismo/complicações , Glomerulonefrite Membranoproliferativa/complicações , Glomerulonefrite Membranoproliferativa/patologia , Humanos , Rim/patologia , Fígado/patologia , Masculino , Nefrite Intersticial/complicações , Nefrite Intersticial/patologiaRESUMO
In their ten years renal biopsy material authors found nine cases of chronic glomerulonephritides with predominantly IgM deposition in the mesangium which reach the diagnosis of IgM nephropathy. This paper on the basis of a typical case deal with the immunopathology, diagnosis, prognosis and therapy of the disease.
Assuntos
Glomerulonefrite Membranoproliferativa/patologia , Adulto , Alopurinol/uso terapêutico , Inibidores da Enzima Conversora de Angiotensina/uso terapêutico , Antimetabólitos/uso terapêutico , Ácido Ascórbico/uso terapêutico , Biópsia , Criança , Doença Crônica , Combinação de Medicamentos , Quimioterapia Combinada , Glomerulonefrite Membranoproliferativa/diagnóstico por imagem , Glomerulonefrite Membranoproliferativa/tratamento farmacológico , Glomerulonefrite Membranoproliferativa/imunologia , Glucocorticoides/uso terapêutico , Humanos , Imunoglobulina M/imunologia , Masculino , Metilprednisolona/uso terapêutico , Prognóstico , Renografia por Radioisótopo , Rutina/uso terapêuticoRESUMO
Binding of the radiolabeled bombesin analog [125I-Tyr4]bombesin to crude cell membranes of MKN45 human gastric cancer grown in nude mice was investigated in vitro. Scatchard analyses of multipoint binding data, performed by complete displacement method demonstrated the presence of two classes of [Tyr4]bombesin binding sites. The high-affinity binding sites had a mean dissociation constant (Kd1) of 2.75 nM with a mean maximal binding capacity (Bmax1) of 492 fmol/mg membrane protein, while the low-affinity binding sites showed a mean dissociation constant (Kd2) of 0.41 microM with a mean maximal binding capacity (Bmax2) of 41.4 pmol/mg membrane protein. Binding of [125(1)-Tyr4]bombesin was specific, reversible and linearly related to the protein concentration of tumor membrane. In displacement studies, the binding of radiolabeled [Tyr4]bombesin was inhibited in a dose-dependent manner by gastrin releasing peptide (GRP)(14-27) and two synthetic antagonists of bombesin/GRP, RC-3095 and RC-3950-II. Both antagonists exhibited high affinity in nearly the same concentration range as GRP(14-27). The presence of receptors for bombesin/GRP on human gastric cancer membranes suggests that bombesin-like peptides may play a role in growth of gastric cancer.
Assuntos
Adenocarcinoma/ultraestrutura , Receptores da Bombesina/metabolismo , Neoplasias Gástricas/ultraestrutura , Adenocarcinoma/metabolismo , Animais , Sítios de Ligação , Ligação Competitiva , Bombesina/análogos & derivados , Bombesina/metabolismo , Membrana Celular/ultraestrutura , Feminino , Humanos , Radioisótopos do Iodo , Cinética , Camundongos , Camundongos Nus , Pessoa de Meia-Idade , Transplante de Neoplasias , Sensibilidade e Especificidade , Neoplasias Gástricas/metabolismo , Transplante Heterólogo , Células Tumorais CultivadasRESUMO
We investigated the effect of bombesin/gastrin-releasing peptide (GRP) antagonist RC-3095 and other analogs on the growth of Hs746T human gastric cancer cells implanted in nude mice or cultured in vitro and on the binding of bombesin to its receptors. Nude mice bearing xenografts of the Hs746T cell line received s.c. injections of RC-3095 (10 micrograms twice daily) or the vehicle (control) for 21 days. Administration of antagonist RC-3095 inhibited the growth of Hs746T tumors. Treatment with RC-3095 produced a significant decrease in tumor volume, prolonged the tumor volume doubling time from 3.6 days to 5.1 days, and decreased the tumor growth rate by 76.9%. The tumor growth delay time in mice treated with RC-3095 was 2.8 days. Treatment with RC-3095 also decreased the final tumor weight by 88.3% and reduced DNA and protein contents in tumors by 91.5% and 89.5%, respectively, as compared to controls. The presence of specific receptors for bombesin/GRP was investigated on the crude membranes of implanted tumors of Hs746T cells. Saturation binding assays showed that the binding of [125I-Tyr4]bombesin to the membranes was saturable and reversible. Scatchard analysis indicated the presence of a single class of binding sites with a high affinity (Kd = 0.24 +/- 0.07 nM) and a low binding capacity (Bmax = 57.0 +/- 0.9 fmol/mg protein). In displacement studies, the binding of [125I-Tyr4]bombesin was inhibited in a dose-dependent manner by unlabelled bombesin(1-14), [Tyr4]-bombesin and GRP (14-27), but not by structurally unrelated peptides. Synthetic bombesin/GRP antagonists RC-3095, RC-3110, and RC-3950-II were all able to inhibit effectively the binding of [125I-Tyr4]bombesin to the membranes of Hs746T cells. RC-3950-II showed a higher binding affinity for bombesin receptors than RC-3095 or RC-3110. Addition of the non-hydrolyzable guanine-nucleotide analog GTP [S] to the binding buffer caused a significant reduction in the amount of [125I-Tyr4]bombesin bound to the cells, indicating that the bombesin receptor is coupled to a G-protein. In cell cultures, bombesin significantly stimulated the growth of Hs746T cells in vitro as shown by an increase in the uptake of [3H]thymidine. Bombesin antagonist RC-3095 could effectively inhibit the bombesin-stimulated growth of Hs746T cells in cultures. These observations suggest that bombesin/GRP may act as growth factors through specific receptors present on the membranes of Hs746T cells. Bombesin/GRP antagonists appear to nullify the effects of bombesin/GRP and may be useful for the treatment of gastric cancers.