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Biomedical subjects

M Takanashi

Publications and source records attributed to M Takanashi.

At least 73 records · Page 4Linked to original sources
PubMed1995

Abolition of suppressive effect of acute myeloid leukemia cells on normal granulocyte-macrophage colony formation induced by interleukin-5 associated with eosinophilic cell induction.

The effects of recombinant interleukin-5 (rIL-5) on leukemic blasts obtained from 22 acute myeloid leukemia (AML) patients were investigated. Recombinant IL-5 stimulated leukemic colony formation in the leukemic blasts of 50% of the patients (11/22), and in 7 of these 11 cell cultures leukemic eosinophilic colonies were induced. Eosinophilic cell induction was associated with cellular proliferation, that is, colony or cluster formation. Leukemic blasts cultured with rIL-5 and forming eosinophilic colonies no longer suppressed normal granulocyte-macrophage colony formation, suggesting that functional differentiation of these leukemic blasts took place. Induction of this type of functional differentiation of leukemic blasts may be of clinical value in promoting normal hematopoiesis.

Acute Disease↗
PubMed1994

Down-regulation of membrane immunoglobulin-associated proteins, MB-1, B29 and Lyn, in AIDS-lymphomas and related conditions.

B-lymphocytes infected with Epstein-Barr virus (EBV) can proliferate in immunocompromised hosts to form lymphomas (MLs). Similar MLs are produced in mice with severe combined immune deficiency (SCID) by transfusion of human lymphocytes infected with EBV (SCID-EBV-positive BML). Mb-1 and B29 are recently found transmembrane proteins associated with membrane immunoglobulins (mIg) on the surface of B cells. Lyn is a src family gene product expressed in B cells submembranously, in association with mIg, possibly through Mb-1/B29 heterodimer. These mIg-associated proteins (Mb-1, B29 and Lyn) are known to mediate antigenic stimulation through mIgs. We noted recently that Lyn is decreased selectively in around a half of SCID-EBV-positive BMLs. We extended this line of investigation to other mIg-associated proteins. Five acquired immunodeficiency syndrome (AIDS)-MLs and ten SCID-EBV-positive BMLs were first analysed by immunohistochemistry for the expression of Mb-1, B29 and Lyn. It was found that in AIDS-MLs, all the mIg-associated proteins were heavily down-regulated. In SCID-EBV-positive BMLs, Mb-1 was down regulated in six of ten, B29 in nine of ten and Lyn in six of ten, whereas no down-regulation was noted in eight EBV-free B MLs that were also maintained in SCID mice. An additional flow-cytometric study of two SCID-EBV-positive and two EBV-negative BMLs showed similar down-regulation in the former cases exclusively. Whereas mIg was also decreased in three of five SCID-EBV positive BMLs, it did not necessarily match the decrease of mIg-associated proteins, which contrasts with the recent finding that mIgs coexist with Mb-1 or B29. Some EBV-encoded proteins may activate host molecules located downwardly; this, in turn, may lead to the suppression of these upwardly-located mIg-associated proteins.

Adult↗
PubMed1994

Pharmacological properties of endothelin receptor subtypes mediating positive inotropic effects in rabbit heart.

The positive inotropic effect (PIE) of endothelin (ET) isoforms, ET-1 and ET-3, was similar in that 1) the PIE was associated with prolongation of isometric contractions, 2) the maximal response was approximately 60% of that to isoproterenol (Isomax), 3) the PIE was associated with acceleration of PI hydrolysis, and 4) it was selectively antagonized by phorbol 12,13-dibutyrate. Because the concentration-response curve for ET-1 was biphasic (whereas that for ET-3 was monophasic), ET-1 had a PIE greater than ET-3 up to 10(-8) M. ET-1 induced a PIE at 3 x 10(-14) M and higher, which reached a plateau of 10-20% of Isomax at 10(-12) M (first phase); the curve became steeper at 10(-9) M and higher (second phase), achieving the maximal response at 10(-7) M to 3 x 10(-7) M. An ETA-selective antagonist, BQ-123, did not affect the PIE of ET-1 up to 10(-7) M; it abolished the first phase at 10(-6) M but did not affect the second phase. BQ-123 at 10(-8) to 10(-6) M antagonized the PIE of ET-3, [Thr2]sarafotoxin S6b, and [Glu9]sarafotoxin S6b in a concentration-dependent manner. The PIE of ET-3 was abolished by 10(-6) M BQ-123. An ETB-selective partial agonist IRL-1620 neither elicited a PIE nor affected the PIE of ET-3. These findings indicate that the PIE of ET receptor agonists on rabbit ventricular myocardium cannot be totally explained by occupancy of the ETA or ETB receptor.

Animals↗
PubMed1993

Engraftment of human non-Hodgkin lymphomas in mice with severe combined immunodeficiency.

BACKGROUND: Malignant non-Hodgkin lymphoma (NHL) is one of the most difficult neoplasms to transplant into nude mice. Mice with severe combined immunodeficiency (SCID) accept various human cancers much more efficiently than do nude mice. The authors investigated whether SCID mice could be used as convenient hosts in which to grow human NHL in vivo. METHODS: Fifty NHL specimens were engrafted into SCID mice. The original specimens and the tumors that developed in SCID mice were studied immunohistologically and by Southern blot analysis to clarify their clonal identity and to determine if they were Epstein-Barr virus (EBV)-transformed B cell proliferations. RESULTS: SCID tumors developed from 23 of 50 NHL specimens. Ten tumors were identical immunophenotypically and, partly, genotypically to the original NHL, showing that the original NHL grew in the SCID mice. B-cell NHL rather than T-cell NHL and high-grade rather than low-grade malignancy groups were much more easily heterotransplanted. Most of the heterotransplanted NHL were maintained by successive transplantation. In two other SCID tumors, the original NHL clones and a newly developed B-cell clone coexisted. The remaining 11 SCID tumors were composed of newly developed clones. The latter 13 tumors were shown to be human cells of B-cell lineage bearing EBV latent proteins--latent membrane protein 1 and EB nuclear antigen 2--suggesting that they originated from EBV-infected B-cells that were present in the original tumor tissues. CONCLUSION: SCID mice accept human NHL far more efficiently than do nude mice. However, frequent occurrence of spontaneous EBV-associated B-cell proliferation must be kept in mind.

Animals↗
PubMed1993

Selective inhibition by phorbol 12,13-dibutyrate of the alpha 1-receptor-mediated positive inotropic effect.

Influence of the protein kinase C activator phorbol 12,13-dibutyrate on the alpha 1- and beta-adrenoceptor-mediated positive inotropic effect was studied in the rabbit ventricular myocardium. Phorbol 12,13-dibutyrate (10(-8)-10(-6) M) inhibited the positive inotropic effect mediated by alpha 1-adrenoceptors in a concentration-dependent manner, while the positive inotropy mediated by beta-adrenoceptors was not affected by phorbol 12,13-dibutyrate up to 3 x 10(-7) M. Phorbol 12,13-dibutyrate at 10(-6) M decreased the beta-mediated effect, but the extent of inhibition was less than that of alpha 1-mediated effect produced by 10(-8) M phorbol 12,13-dibutyrate. Thus, the inhibition induced by phorbol 12,13-dibutyrate was 100-fold more selective for alpha 1- than for beta-mediated inotropy. Phorbol 12,13-dibutyrate at 10(-7) M increased the basal force of contraction in some preparations, but decreased it at 3 x 10(-7) M and higher in a concentration-dependent manner. In membrane fractions derived from the rabbit ventricular muscle, phorbol 12,13-dibutyrate did not affect the specific binding of [3H]prazosin. A nonhydrolyzable GTP analogue GTP gamma S shifted the epinephrine-induced displacement curve of [3H]prazosin to the right, but phorbol 12,13-dibutyrate did not affect the curve. Accumulation of [3H]inositol monophosphate induced by alpha 1 stimulation was inhibited by phorbol 12,13-dibutyrate. These findings indicate that phorbol 12,13-dibutyrate may induce the selective uncoupling of the myocardial alpha 1-receptor stimulation to activation of phospholipase C, and inhibit selectively the alpha 1-mediated positive inotropy.

Animals↗
PubMed1993

Pronounced direct inhibitory action mediated by adenosine A1 receptor and pertussis toxin-sensitive G protein on the ferret ventricular contraction.

An adenosine A1 receptor agonist R-N6-phenylisopropyladenosine (R-PIA) elicited a pronounced negative inotropic effect with the EC50 value of 0.69 mumol/l in the presence of a beta-adrenoceptor blocking agent bupranolol (0.3 mumol/l) in the isolated ferret papillary muscle. The negative inotropic effect of R-PIA was not associated with changes in cyclic AMP level. Adenosine and other A1 receptor agonists also elicited a negative inotropic effect. DPCPX (1,3-dipropyl-8-cyclopentyl xanthine) antagonized the negative inotropic effect of R-PIA in a competitive manner (pA2 value = 8.4). The inhibitory action of R-PIA was markedly attenuated in the ventricular muscle preparation isolated from ferrets pretreated with pertussis toxin that caused ADP-ribosylation of 39 kDa proteins in the membrane fraction. In the membrane fraction derived from the ferret ventricle, [3H]-DPCPX bound to a single binding site in a saturable and reversible manner with high affinity (Kd value = 1.21 +/- 0.41 nmol/l; Bmax = 12.8 +/- 3.02 fmol/mg protein; n = 7). The binding characteristics of [3H]-DPCPX in the rat ventricle (Kd value = 1.51 +/- 0.09 nmol/l; Bmax = 12.7 +/- 1.47 fmol/mg protein; n = 5) were similar to those in the ferret. On the other hand, the content of G(o), a major pertussis toxin-sensitive G protein in the ferret heart, was much higher in the ferret than in the rat ventricle. The present results indicate that adenosine receptors may play an important role in the inhibitory regulation of ventricular contractility in the ferret in contrast to other mammalian species. The signal transduction process subsequent to agonist binding to A1 receptors including the pertussis toxin-sensitive G protein and ion channels may be responsible for the unique inhibitory action of adenosine in this species.

Adenosine Diphosphate Ribose↗
PubMed1993

The effects of leukemia inhibitory factor and interleukin 6 on the growth of acute myeloid leukemia cells.

The effects of leukemia inhibitory factor (LIF) and interleukin 6 (IL-6) on blast progenitors from acute myeloblastic leukemia (AML) were examined using a blast colony assay in a serum-free culture system. LIF and IL-6 stimulated colony growth in 2 and 5, respectively, of 11 cases studied. The simultaneous addition of LIF with granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin 3 (IL-3) or IL-6 produced a statistically significant increase of colony numbers in 3, 6 and 7 of 11 cases, respectively. Numbers of colonies increased significantly when IL-6 was added simultaneously with GM-CSF or IL-3 in 5 and 4 of 11 cases, respectively. LIF or IL-6 used in the primary culture did not significantly change the numbers of secondary colonies compared to GM-CSF. Previous exposure to LIF and IL-6 did not alter cellular phenotype or morphology, indicating that LIF and IL-6 did not induce the differentiation of fresh AML blasts.

Adult↗
PubMed1993

Inotropic effects of staurosporine, NA 0345 and H-7, protein kinase C inhibitors, on rabbit ventricular myocardium: selective inhibition of the positive inotropic effect mediated by alpha 1-adrenoceptors.

The influence of protein kinase C (PKC) inhibitors, staurosporine, NA 0345 and H-7, on the alpha 1- and beta-adrenoceptor-mediated positive inotropic effect (PIE) was studied in rabbit ventricular myocardium. Staurosporine (1-10 nM), NA 0345 (10-100 nM) and H-7 (1-10 microM) selectively attenuated the PIE mediated by alpha 1-adrenoceptors at concentrations that did not affect the beta-mediated PIE and basal force of contraction. Staurosporine at higher concentrations (> 10 nM) decreased the basal force, while NA 0345 and H-7 did not. In membrane fractions derived from rabbit ventricular muscle, neither staurosporine, NA 0345 nor H-7 modified the specific [3H]prazosin binding at the concentrations that elicited the functional modulation. Accumulation of [3H]inositol monophosphate (IP1) induced by alpha 1-adrenoceptor stimulation was not affected by the PKC inhibitors. Phorbol 12,13-dibutyrate (PDBu), a PKC activator, also selectively attenuated the alpha 1-mediated PIE, but in association with the inhibition of the alpha 1-mediated IP1 accumulation. Staurosporine (1 nM), but not H-7, antagonized the PDBu-induced inhibitory action on the alpha 1-mediated PIE. These findings indicate that staurosporine, NA 0345 and H-7 produce a selective inhibition of the alpha 1-mediated PIE, probably through inhibition of the alpha 1-adrenoceptor-mediated activation of PKC. On the contrary, externally administered phorbol ester may act by uncoupling of alpha 1-adrenoceptors to activation of phospholipase C through a pathway different from endogenous diacylglycerol to lead to a selective inhibition of the alpha 1-mediated PIE.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

On the mechanism of action of the beta-1 partial agonist denopamine in regulation of myocardial contractility: effects on myocardial alpha adrenoceptors and intracellular Ca++ transients.

Experiments were carried out to study the effects of denopamine on myocardial alpha-1 adrenoceptors in the rabbit and on intracellular Ca++ transients in the dog ventricular muscle. Denopamine displaced the specific binding of the alpha-1 receptor antagonist [3H]prazosin with high and low affinities in the membrane fraction derived from the rabbit ventricle. The positive inotropic effect (PIE) of denopamine, however, was not affected by prazosin. A beta receptor antagonist bupranolol antagonized the PIE of denopamine in a concentration-dependent manner. In the rabbit denopamine acted as a beta receptor partial agonist with an intrinsic activity of 0.8 and shifted the concentration-response curve for isoproterenol to the right (Kp = 1.5 microM). In addition, denopamine attenuated the maximal inotropic response to phenylephrine mediated by alpha-1 receptors, but did not affect the pD2 value for phenylephrine. In isolated dog right ventricular muscle, the bell-shaped concentration-response relationship for the inotropic effect of denopamine was associated with coinciding increase and decrease in the amplitude of aequorin light transients. The relationship between the increase in peak Ca++ transients and developed tension in response to denopamine was the same as the relation during administration of isoproterenol. The present results indicate that denopamine binds myocardial alpha-1 adrenoceptors with high affinity and may thereby inhibit the maximal response of phenylephrine mediated by alpha-1 receptors. The PIE of denopamine is mediated exclusively by beta receptors. The change in Ca++ sensitivity caused by denopamine may not be different from that induced by a beta receptor full agonist isoproterenol.

Adrenergic beta-Agonists↗
PubMed1993

Expression of Lyn protein on human malignant lymphomas.

BACKGROUND: lyn is one of the src family genes encoding protein-tyrosine kinases, expressed preferentially in B lymphocytes and monocytes/macrophages. Its gene product, Lyn protein, is thought to participate in cell membrane-associated signal transduction on B lymphocytes by associating physically and functionally with membrane-bound IgM. EXPERIMENTAL DESIGN: To investigate the expression of Lyn on human malignant lymphomas (MLs), 50 ML biopsies, 12 ML samples maintained in mice with severe combined immunodeficiency, and 4 African Burkitt type cell lines were studied with the use of immunohistology, immunochemistry, and Southern blot analysis. RESULTS: Among biopsy specimens, 27 of 27 B-MLs, 5 of 21 T-MLs, and 2 of 2 null-MLs were stained. In severe combined immunodeficiency mouse-maintained B-MLs, unlike biopsied B-MLs, 4 of 11 were found to be unstained. Further analysis disclosed that all 4 of these unstained B-MLs were the Epstein Barr virus transformed B cells proliferating in severe combined immunodeficiency mice and not the original ML cells, suggesting the presence of a specific mechanism down-regulating the Lyn protein in this group. One IgA+ IgM- B-ML and one IgG+ IgM- B-ML were stained by the antibody, indicating the possible existence of molecular mechanisms other than membrane-bound IgM that facilitate Lyn protein expression. Decrease of Lyn expression was also noted in 3 of 4 Epstein-Barr virus-positive African Burkitt's ML lines. Complementary Western blot analysis of 8 immunostained and 4 unstained MLs confirmed the immunohistologic findings. However Southern blot analysis showed that the lyn gene in Lyn-positive and -negative cases were apparently unchanged. CONCLUSIONS: The level of Lyn expression in MLs reflects mainly their normal counterpart, whereas it can be expressed somewhat differently in some cases, especially in Epstein Barr virus-transformed MLs that occur in immunocompromised hosts, on which it is often down-regulated. This is the first report of Lyn expression on human MLs.

Animals↗
PubMed1992

Effect of (+)-niguldipine on myocardial alpha 1-adrenoceptors in the rabbit.

The influence of the alpha 1A-adrenoceptor subtype-selective antagonist (+)-niguldipine on the alpha 1-mediated positive inotropic effect was assessed in the isolated rabbit ventricular myocardium. (+)-Niguldipine displaced the specific binding of [3H]prazosin to a membrane fraction derived from rabbit ventricular muscle with high (Ki = 64.6 pmol/l; RH = 23%) and low (Ki = 7.08 nmol/l) affinity. (+)-Niguldipine displaced specific [3H]CGP-121177 binding only at very high concentrations (Ki = 118 nmol/l). (+)-Niguldipine at 0.1 pmol/l and higher shifted the concentration-response curve for the alpha 1-mediated positive inotropic effect downwards, but at higher concentrations (up to 10 and 100 nmol/l) it did not cause a further shift of the curve. (+)-Niguldipine (1-100 nmol/l) did not affect the beta-mediated positive inotropic effect and the basal force of concentration. (-)-Niguldipine also showed a selective inhibitory action on the alpha 1-adrenoceptor-mediated positive inotropic effect, but its affinity and potency were approximately 1-2 log units lower than those of (+)-niguldipine. The present results indicate that the alpha 1A-adrenoceptor subtype is involved in the alpha 1-mediated positive inotropic effect. (+)-Niguldipine (or (-)-niguldipine with lower affinity) is able to antagonize selectively the cardiac alpha 1A-adrenoceptor-mediated positive inotropic effect. The magnitude of the alpha 1A-mediated inotropic effect, however, may be much less than that mediated by the alpha 1B-subtype in the rabbit ventricular myocardium.

Adrenergic alpha-Antagonists↗
PubMed1992

Effects of vasopressin on phosphoinositide hydrolysis and myocardial contractility.

The effects of vasopressin on phosphoinositide hydrolysis, ventricular contractility and adrenoceptor-mediated inotropy were studied in the rabbit. Vasopressin caused an accumulation of [3H]inositol monophosphate in ventricular slices prelabelled with myo-[3H]inositol, whereas it elicited a small but definite negative inotropic effect. In addition, vasopressin attenuated the positive inotropic effect elicited via alpha 1- and endothelin receptors without affecting the beta-adrenoceptor-mediated effect. The nonpeptide-selective V1 receptor antagonist OPC 21268 (a quinolinone derivative) inhibited the vasopressin-induced accumulation of [3H]inositol monophosphate. The present results indicate that vasopressin stimulates phosphoinositide hydrolysis via V1 receptors, but inhibits force and the alpha 1-mediated positive inotropic effect in the rabbit ventricular myocardium.

Animals↗
PubMed1992

Role of alpha 1A adrenoceptor subtype in production of the positive inotropic effect mediated via myocardial alpha 1 adrenoceptors in the rabbit papillary muscle: influence of selective alpha 1A subtype antagonists WB 4101 and 5-methylurapidil.

In order to elucidate the contribution of alpha 1A subtype to the positive inotropic effect mediated by myocardial alpha 1 adrenoceptors, the influence of the alpha 1A selective antagonists WB 4101 and 5-methylurapidil on the alpha 1-mediated positive inotropic effect (induced by phenylephrine in the presence of a beta adrenoceptor blocking agent bupranolol) was assessed in the isolated rabbit papillary muscle. WB 4101 (10(-9)-10(-7) mol/l) shifted the concentration-response curve of the alpha 1-mediated positive inotropic effect to the right in parallel, but the slope of Schild plot did not meet the competitive antagonism: WB 4101 shifted the curve by log one unit at 10(-9) mol/l, whereas it did not cause further shift at higher concentrations of 10(-8) and 10(-7) mol/l. WB 4101 did not affect the beta adrenoceptor-mediated positive inotropic effect. 5-Methylurapidil (10(-9) to 10(-7) mol/l) shifted the curve of alpha 1-mediated positive inotropic effect to the right and downwards in a concentration-dependent manner; the slope of Schild plot calculated at the level of 20% of the maximum response to phenylephrine was close to unity. 5-Methylurapidil at 3 x 10(-7) mol/l abolished the alpha 1-mediated positive inotropic effect. In addition, 5-methylurapidil inhibited the beta adrenoceptor-mediated positive inotropic effect in the same concentration range as it antagonized the alpha 1-mediated positive inotropic effect, indicating that 5-methylurapidil is not selective for myocardial alpha 1 adrenoceptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1992

A case of transfusion-associated graft-versus-host disease not prevented by white cell-reduction filters.

A case of transfusion-associated graft-versus-host disease (TA-GVHD) in a patient with non-Hodgkin's lymphoma is reported. The patient, a 67-year-old woman, was diagnosed as having diffuse, mixed type non-Hodgkin's lymphoma, at clinical stage IIIA. She was treated with combination chemotherapy and received multiple blood transfusions for anemia and thrombocytopenia. Although white cells (WBCs) were reduced in the transfused components by WBC-reduction filters, the patient developed TA-GVHD that was confirmed by skin biopsy. It is suggested that the WBC reduction attained with these filters does not prevent TA-GVHD in immunocompromised patients. It is recommended that all blood components should be irradiated before transfusion to such patients.

Aged↗
PubMed1992

Identification of the carboxymethyllysine residue in the advanced stage of glycated human serum albumin.

As an advanced stage of glycation, glycated human serum albumin (G-HSA; glucose content, 2 mol of 5-hydroxymethylfurfural equivalent/mol of HSA) was incubated at 37 degrees C up to 30 d in 0.2 M phosphate buffer, pH 7.4, with 100 microM Fe3+. G-HSA incubated for 30 d (G-HSA-30(Fe)) was subsequently hydrolyzed at 110 degrees C for 24 h in 6 N HCl. In the hydrolysate, N epsilon-carboxymethyllysine (CML) was identified by cochromatography with synthesized CML on an amino acid analyzer. pI of HSA (4.8) shifted to 4.5 in G-HSA. A more acidic fraction, pI 4.3, appeared in G-HSA-30(Fe). CML content (mol of CML/mol of HSA) of HSA and G-HSA was as follows; 0 in HSA, 0.2 in HSA-30(Fe), 0.4 in G-HSA and 1.5 in G-HSA-30(Fe) pI 4.3. The amino acid compositions also changed in lysine, arginine and tyrosine at the advanced stage of the reaction.

Arginine↗
PubMed1992

Concentration- and time-dependence of phosphoinositide hydrolysis induced by endothelin-1 in relation to the positive inotropic effect in the rabbit ventricular myocardium.

The effects of endothelin-1 on phosphoinositide hydrolysis in relation to the positive inotropic effect of the compound were studied in the rabbit ventricular myocardium. Endothelin-1 elicited a concentration- and time-dependent accumulation of [3H]inositol monophosphate (IP1) in ventricular muscle slices prelabeled with myo-[3H]inositol in concentrations similar to those that caused a positive inotropic effect. The EC50 value of endothelin-1, both for the induction of [3H]IP1 accumulation and for the positive inotropic effect was 6 x 10(-9) M. The endothelin-induced positive inotropic effect was linearly related to [3H]IP1 accumulation. Endothelin-1 induced a small transient negative inotropic effect before the onset of a gradually developing and sustained positive inotropic effect which reached a steady level at 30 min. After administration of endothelin-1, [3H]IP3 accumulated rapidly and transiently before the development of the positive inotropic effect. [3H]IP2 accumulated slowly and peaked at 20 min. [3H]IP1 accumulation occurred more slowly and of the inositol phosphates its time course coincided best with that of the positive inotropic effect. Phorbol 12,13-dibutyrate inhibited both the [3H] IP1 accumulation and positive inotropic effect induced by endothelin-1. The present results indicate that an acceleration of phosphoinositide hydrolysis induced by activation of endothelin-1 receptors may be responsible for induction of the positive inotropic effect of endothelin-1 on rabbit ventricular myocardium.

Animals↗
PubMed1992

Characterization of [3H]YM617, R-(-)-5-[2-[[2[ethoxyring(n)-3H](o-ethoxyphenoxy)ethyl]amino]- propyl]-2-methoxybenzenesulfonamide HCl, a potent and selective alpha-1 adrenoceptor radioligand.

The binding properties of a new radioligand, R(-)-5-[2-[[2[ethoxyring(n)-3H](o- ethoxyphenoxy)ethyl]amino]propyl]-2-methoxybenzenesulfonamide++ + HCl ([3H]YM617), were studied in membranes of the rat hippocampus and spleen. [3H]YM617 rapidly associated with its binding sites in both membranes and reached steady state by 20 min at 25 degrees C. The specific binding of [3H]YM617 appeared to be saturable, and Scatchard analysis revealed a linear plot, suggesting a single population of binding sites with a dissociation constant of 0.170 +/- 0.016 nM (n = 6) in the hippocampus and 0.195 +/- 0.036 (n = 4) in the spleen. The maximal binding sites in the hippocampus and spleen were 203.0 +/- 43.2 (n = 6) and 72.4 +/- 17.0 (n = 4) fmol/mg protein, respectively. Chlorethylclonidine (10(-5) M for 10 min) treatment reduced the Bmax values of [3H]YM617 and [3H]prazosin to a similar degree in the rat hippocampus (10-15%) and spleen (40-50%). Alpha adrenoceptor agonists and antagonists competed with [3H]YM617 for binding sites in the following order: YM617 > prazosin > WB4101 > bunazosin > 5-methylurapidil > S(+)-isomer of YM617 > phentolamine > yohimbine > norepinephrine = phenylephrine > methoxamine in the hippocampus, and prazosin > YM617 > bunazosin > WB4101 > 5-methylurapidil > phentolamine > S(+)-isomer of YM617 > yohimbine > norepinephrine > phenylephrine > methoxamine in the spleen. In the hippocampus, prazosin and bunazosin produced biphasic displacement of [3H]YM617, but not [3H]prazosin binding. In contrast, only monophasic curves were obtained against either radioligand in the spleen.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Agonists↗