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J E Wikberg

Publications and source records attributed to J E Wikberg.

At least 145 records · Page 8Linked to original sources
PubMed1984

Photoaffinity cross-linking of a radioiodinated probe, 125I-A55453, into alpha 1-adrenergic receptors.

We have synthesized and characterized a high-affinity alpha 1-adrenergic receptor probe, 4-amino-6,7-dimethoxy-2[4'- [5"(3"'-125I-iodo-4"'-aminophenyl)pentanoyl]-1'-piperazinyl] quinazoline (125I-A55453). This ligand binds reversibly to rat hepatic plasma membranes with high affinity (KD = 77 +/- 6 pM), and it labels the same number of "specific" prazosin-competable sites as the alpha 1-adrenergic receptor-selective radioligand [125I] iodo-2-[beta-(4-hydroxyphenyl)-ethylaminomethyl]tetralone. Specific binding is stereoselective and competed for by alpha-adrenergic agents with an alpha 1-adrenergic receptor specificity. 125I-A55453 can be covalently photoincorporated into peptides of rat hepatic and splenic membranes using the bifunctional photoactive cross-linker, N-succinimidyl-6- (4'-azido-2'-nitrophenylamino)hexanoate. Following photolysis, sodium dodecyl sulfate-polyacrylamide gel electrophoresis of labeled hepatic membranes reveals a major "specifically" labeled peptide of Mr = 82,000 (+/- 1,000) with minor peptides at Mr = 50,000 (+/- 500), and 40,000 (+/- 300). Covalent incorporation of 125I-A55453 into the Mr = 82,000 peptide is inhibited by adrenergic drugs with an alpha 1-adrenergic receptor specificity. Labeled splenic membranes demonstrate a broad band of photoincorporated radioactivity centered at Mr = 82,000, and covalent incorporation into this peptide is also attenuated with an alpha 1-adrenergic receptor specificity. This new high-affinity radioiodinated probe has features which should make it useful for the molecular characterization of alpha 1-adrenergic receptors in tissues.

Affinity Labels↗
PubMed1983

Solubilization of rat liver alpha 1-adrenergic receptors. Agonist specific alteration in receptor binding affinity.

An improved method for the solubilization of the alpha 1-adrenergic receptors in rat liver, utilizing digitonin, glycerol and sonication, is described. The yield of solubilized receptors was approximately 20%. The soluble receptors showed characteristics similar to the membrane-bound alpha 1 receptors. However, upon solubilization, the affinity for the agonists (-)norepinephrine and (-)epinephrine increased 35- to 66-fold when compared to the affinity in the membranes. The affinity for antagonists remained unchanged. A number of synthetic partial agonists showed a less marked (5- to 10-fold) increase in affinity upon solubilization. These data are consistent with the notion that these receptors might be capable of existing in two distinct conformational states with the high affinity state for agonists being favored by solubilization.

Adrenergic alpha-Agonists↗
PubMed1983

Norepinephrine-induced down regulation of alpha 1 adrenergic receptors in cultured rabbit aorta smooth muscle cells.

Drug-induced refractoriness of alpha-adrenergic receptor-mediated vasoconstriction may be a clinically important phenomenon. We have investigated the possible molecular mechanisms underlying this phenomenon in cultured vascular smooth muscle cells derived from the rabbit aorta. alpha 1-Adrenergic receptors were identified in membranes prepared from these cells by [125I]HEAT binding. The radioligand bound to a high affinity site (Kd = 140 pM) in a saturable fashion (202 fmol/mg protein). Adrenergic agonists and antagonists competed for binding of [125I]HEAT with the expected order of potency for an alpha 1-receptor, (-)epinephrine greater than or equal to (-) norepinephrine greater than (+)epinephrine greater than isoproterenol and prazosin greater than phentolamine greater than yohimbine. Exposure of cells for 26 hours to 10 microM norepinephrine resulted in a 70% decrease in the number of alpha 1-receptors as measured by [125I]HEAT binding without any significant change in the affinity of the receptor for the ligand. When the alpha-receptors were blocked with 10 microM phentolamine the loss of receptors induced by norepinephrine was completely prevented. Similar down-regulation of the [125I]HEAT binding sites was observed when the alpha 1-agonist phenylephrine was used instead of norepinephrine. It is concluded that alpha-agonists induce down-regulation of aortic smooth muscle alpha 1-receptors. This reduction of alpha-receptors could be important in the mechanisms by which vascular smooth muscle develops refractoriness to alpha-adrenergic stimulation.

Adrenergic alpha-Antagonists↗
PubMed1983

Covalent labeling of the cerebral cortex alpha 1-adrenergic receptor with a new high affinity radioiodinated photoaffinity probe.

A novel high affinity radioiodinated photoaffinity probe, 4-amino-6,7-dimethoxy-2[4-[5(3-[125I]iodo-4-azidophenyl)pentanoyl]-1- piperazinyl]-quinazoline, structurally related to the potent alpha 1-adrenergic antagonist prazosin, was developed and used to covalently label the rat cerebral cortex alpha 1-adrenergic receptor. In the absence of light, this ligand binds to cortex plasma membranes with a dissociation constant of 308 pM and with a maximal number of binding sites of 200 fmol/mg protein. Upon photolysis, the ligand incorporates irreversibly into plasma membrane proteins. Autoradiograms of such membrane samples subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveal a major specifically labeled polypeptide at Mr = 79,000. The covalent incorporation into the peptide at Mr = 79,000 can be inhibited by several adrenergic receptor ligands with a typical alpha 1-adrenergic receptor specificity and stereoselectivity.

Affinity Labels↗
PubMed1982

Adrenergic receptors: classification, ligand binding and molecular properties.

The interaction of catecholamines and drugs with adrenergic receptors leads to a set of biochemical reactions which ultimately results in a physiological response. A brief review is given of the classification of adrenergic receptors into subtypes and the use of ligand binding techniques for the identification and characterization of these receptors. Recent advances in the biochemistry of adrenergic receptors are reviewed with special reference to the interaction of the beta and alpha 2-receptors with guanine nucleotide regulatory proteins and adenylate cyclase. The role of calcium and phosphoinositides in the function of the alpha 1-receptor is also discussed.

Animals↗
PubMed1982

Pharmacology of B-HT 920 in some isolated smooth muscles of the guinea-pig.

The effects of B-HT 920 were investigated on four isolated preparations from the guinea-pig, namely the aorta, trachea, ileum and vas deferens. The latter three preparations were studed during electrical field stimulation, which induced contractions by activating cholinergic neurones (trachea and ileum) or adrenergic neurones (vas deferens), respectively. Comparative studies were also made with clonidine and noradrenaline. In ileum and trachea B-HT 920 was almost equipotent with noradrenaline to inhibit the electrically induced contractions. In these tissues, B-HT 920 also displayed almost the same maximal effect as noradrenaline. Clonidine also inhibited the contractions in ileum and trachea; the drug was slightly more potent than noradrenaline. However, in contrast to the intrinsic activity of B-HT 920 that of clonidine was only submaximal. In vas deferens both B-HT 920 and clonidine induced inhibition of contractions on electrical field stimulation at low concentrations. In this organ, both drugs were capable of inducing complete inhibition of the contractile response. In aorta B-HT 920 as well as clonidine were only weak agonists in comparison to noradrenaline. The alpha2-blocker, yohimbine, completely blocked the effect of B-HT 920 in ileum at low concentrations (1 x 10(-7) M). Remarkably, however, the inhibitory action of B-HT 920 in trachea was only marginally affected even by high concentrations of yohimbine (1 x 10(-6) M). It is suggested from the present results that B-HT 920 can induce inhibition of both cholinergic and adrenergic neurotransmission presumably by inducing selective stimulation of prejunctional alpha2-receptors. In fact, the selectivity of B-HT 920 seems to be comparable to that of clonidine for the alpha2-receptor. However, the mode of action of B-HT 920 in trachea may be somewhat uncertain since its effect was not inhibited by yohimbine.

Animals↗
PubMed1982

Vascular smooth muscle relaxation by nitro compounds: reduced relaxation and cGMP elevation in tolerant vessels and reversal of tolerance by dithiothreitol.

Smooth muscle preparations obtained from bovine mesenteric artery were incubated with high concentrations of nitroglycerin (NG) or nitroprusside (NP) at elevated pH. This treatment was found to make the vessels tolerant towards both the relaxant and cGMP elevating action of a challenging dose of nitrocompounds when tested on the histamine contracted vessels. Also, some cross-tolerance between NP and NG could be found since pretreatment of the vessels with NP caused a reduction in both the relaxant and the cGMP elevating action of NG. The NG induced tolerance could be partly reversed by treatment with the disulfide reducing agent dithiothreitol (DTT). These results are suggested to strengthen the evidence for cGMP as a mediator of vascular smooth muscle relaxation induced by nitrocompounds. The ability of DTT to partly reverse this tolerance indicates the existence of critical tissue sulfhydryl groups with which the nitrocompounds interact. There also seemed to exist certain differences in the mechanism of action between NG and NP since the tolerance induced against NG was much more pronounced than was the case for NP.

Animals↗
PubMed1982

Relaxant beta-receptors in the trachea, but not prejunctional alpha 2-receptors in the tracheal cholinergic neurones, are subjected to homologous desensitization.

Guinea-pigs were pretreated with either isoprenaline, terbutaline or the alpha 2 agonist B-HT 920 in order to asses the hypothesis that beta-and alpha 2 receptors in trachea are subjected to homologous desensitization. In these experiments the beta receptor activity was investigated on tracheal ring preparations contracted with carbacholine. Both in the isoprenaline and the terbutaline pretreated group the relaxant responses to beta agonists were diminished. Pretreatment with B-HT 920 did not affect the sensitivity of the trachea to beta stimulation. In order to asses the responsiveness of alpha 2 receptors the trachea was contracted by electrical field stimulation in the presence of propranolol. During these conditions contractions were mediated by activation of cholinergic neurones and inhibitory effects of alpha stimulation were due to inhibition of the cholinergic neurotransmission by stimulation of prejunctional alpha 2 receptors. In these tests neither isoprenaline, terbutaline nor B-HT 920 pretreatment affected the responsiveness of alpha stimulation to inhibit the electrically induced contractions.

Animals↗
PubMed1982

Inhibitory effects of different retinoids (vitamin A analogues) on the stimulated rat liver guanylate cyclase activity.

Vitamin A and its analogues show the ability to prevent malignant cell transformation on induction with different carcinogens, such as nitrosamines. Cyclic GMP has been proposed as a positive modulator of malignant cell growth and the cGMP-forming enzyme guanylate cyclase is strongly stimulated by e.g. nitrosamines. In this study, we found that retinylacetate and retinal were very potent inhibitors of the stimulated guanylate cyclase. When a series of structurally different retinoids were tested in the same system, a wide range of inhibitory activity on guanylate cyclase was found for the different retinoids with some being completely ineffective. The most potent inhibitor was retinylacetate. Furthermore, the inhibitory profile of the retinoids on the guanylate cyclase did not seem to correlate to their in vivo activity as antineoplastic agents, as described in the literature. We therefore conclude that there does not exist a general connection between the anticancer activity and the guanylate cyclase inhibition of the retinoids. However, it can not be excluded that the guanylate cyclase inhibition might be of importance for the antineoplastic activity for some of the retinoids.

Animals↗
PubMed1981

Purification of human basophils by affinity chromatography on anti-IgE-sepharose 6MB.

This work describes a method for the purification of basophil leukocytes from human peripheral blood by the use of a three-step separation technique including affinity chromatography on anti-IgE-sepharose 6MB. The purity of the obtained basophils was 50--95% and the recovery was 30--40%. The basophils separated by this method appeared normal and were found to be reactive with anti-IgE in subsequent tests.

Antibodies, Anti-Idiotypic↗
PubMed1981

Investigations on the occurrence of cytidine 3',5' monophosphate (cCMP) in tissues.

A specific and sensitive radioimmunoassay (RIA) for the detection of cCMP was developed. Antibodies were prepared by immunization of rabbits with succinyl cCMP conjugated to human albumin. In the RIA commercially available 3H-cCMP was used as labeled antigen. Low amounts (0.4-2.6 pmol/g w.wt.) of immunoreactive material could be detected in extracts of brain, heart, ileum, kidney, liver, lung, spleen, testis and uterus from rats, guinea-pig and frogs. The immunoassayable material in rat liver was subjected to column chromatography on AG 1-X8 anion exchange resin. The radioimmunoassayable material isolated from the liver did not cochromatograph with authentic tritiated or unlabeled cCMP. The chromatographic properties of the immunoreactive material did not change in regenerating livers - following partial hepatectomy, or after pronase treatment. However, after treatment with pronase the amount of assayable material, extracted from the rat liver, increased. It is suggested that cCMP - as such - is not present, in detectable amounts, in extracts prepared by commonly used procedures for isolation of cyclic nucleotides. The chemical nature of the cCMP immunoreactive material isolated from rat liver is at present unclear.

Animals↗
PubMed1981

Pharmacological characterization of the autonomous innervation of the guinea pig tracheobronchial smooth muscle.

From the trachea, main bronchi and hilus bronchi of guinea pigs, preparations were isolated for registration of mechanical tension on electrical field stimulation and drugs. The trachea contracted on short trains of electrical stimulation. Usually these contractions were followed by a relaxant response. The contractions were abolished while the relaxations were potentiated by atropine. In the main bronchi field stimulation induced a contractile response which was abolished by atropine. In the latter preparation relaxant responses were never observed, even not after atropine. In the trachea and main bronchi neither the alpha 1 blocker prazosin nor the alpha2 blocker yohimbine affected the contractile or relaxant responses when used in alpha-blocking concentrations. The relaxant response in trachea was neither affected by the "P1 blocker" theophylline nor by the "P2 blocker" quinidine but it was partially inhibited by guanethidine or beta-blocking agents. The hilus bronchi contracted on field stimulation as well as histamine. The contractile response on electrical stimulation was only slightly inhibited by atropine or guanethidine. In all three preparations responses on field stimulation were abolished by tetrodotoxin. It is suggested that in both trachea and main bronchi excitatory cholinergic innervation is present. Further, the trachea but not the main bronchi is innervated by both adrenergic and nonadrenergic inhibitory nerves. The hilus bronchi contains a non-adrenergic non-cholinergic excitatory nervous system.

Animals↗
PubMed1981

Correlation between vascular smooth muscle relaxation and increase in cyclic GMP induced by some organic nitro esters.

Three different nitro compounds glyceryl mononitrate (GMN), glyceryl dinitrate (GDN) and ethylene glycol dinitrate (EGDN) were tested on histamine contracted bovine mesenteric artery. GDN and EGDN caused a dose-dependent relaxation which was accompanied by an increase in the endogenous cGMP level. The ED50-value for GDN and EGDN with regard to the relaxant action was 1.06 X 10(-6) M and 4.20 X 10(-8), respectively. GMN was almost completely ineffective as a relaxing agent and did not cause any significant change in cGMP. Regression analysis revealed a significant correlation between relaxation and increase in cGMP for both GDN and EGDN. The regression model for EGDN could be significantly improved by including the squared cGMP change, indicating a non-linear relationship. With regard to GDN a hyperbolic relationship between relaxation and cGMP increase was found. A slight improvement of the regression model was found for EGDN when the change in cAMP was included. For GMN and GDN no improvement of the regression model could be revealed by including the change of cAMP. It is suggested that the present data give further evidence for cGMP as a mediator of vascular smooth muscle relaxation induced by nitro compounds.

Animals↗
PubMed1981

Characterization of 5-hydroxytryptamine uptake in sliced rat lung.

Slices of rat lung were incubated with tritiated 5-hydroxytryptamine and the tissue uptake of tritium was studied after separating the free and bound radioactivity by filtration on glass fiber filters. At 37 degrees a rapid uptake occurred during the first 10 min. After that time the uptake was less marked but it was still present after 60 min. The uptake was moderately potentiated by the MAO inhibitor iproniazid (3 micrometers) after 30-60 min. incubation. The 5-hydroxytryptamine uptake was inhibited by some uptake inhibitors, their order of potency beeing: clomipramine greater than imipramine greater than or equal to nortriptyline greater than or equal to cocaine greater than or equal to desipramine greater than maprotiline. At 0 degrees the uptake of 5-hydroxytryptamine was negligible. Non-linear regression analysis of uptake data indicated that 5-hydroxytryptamine was taken up by two different mechanisms. One of the uptake processes was saturated by high concentrations of 5-hydroxytryptamine and showed an apparent Km of 8 X 10(-7) M. The other uptake was linearly related to the 5-hydroxytryptamine concentration and could not be saturated even by concentration up to 5 X 10(-5) M of the amine.

Animals↗