Beta-3 versus beta-2 adrenergic agonists and preterm labour: in vitro uterine relaxation effects

In this study of nervous control of exocrine secretion, electrical field stimulation (FS) evoked a marked, tetrodotoxin-sensitive increase in the amylase output from in vitro segments of rat pancreas. Blockade of the large cholinergic component of the response by atropine revealed a smaller noncholinergic nerve-mediated secretion. This noncholinergic secretion was unaffected by phentolamine but abolished by propranolol, as were the secretory responses to norepinephrine and other beta-adrenergic agonists. FS also produced an increase in the efflux of radiolabeled norepinephrine from preloaded tissue that was tetrodotoxin sensitive and calcium dependent. Although FS and the adrenergic secretagogues had no effect on 45Ca2+ metabolism or acinar cell electrical properties of atropine-treated rat pancreas, they both evoked increases in tissue cAMP levels. These increases in cAMP concentration were also blocked by propranolol. The phosphodiesterase inhibitor isobutylmethylxanthine potentiated both the elevation of cAMP levels and the amylase secretion evoked by adrenergic stimulation. Since both specific beta 1- and beta 2-adrenergic agonists elevated cAMP levels and caused amylase secretion, it appears that both beta-receptor subtypes are present in the rat pancreas. Of the selective beta 1- and beta 2-antagonists used, the most pronounced reduction, but not complete blockade, of the FS- and norepinephrine-induced cyclic nucleotide and secretory effects was obtained with the beta 1-antagonist metoprolol. It is concluded that stimulation of adrenergic nerves in the rat pancreas evokes an amylase secretion that is mediated via the activation of mainly beta 1-type adrenergic receptors and the utilization of cAMP as an intracellular second messenger.

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Acute change in the cyclic AMP content of rat mammary acini in vitro. Influence of physiological and pharmacological agents

Biochemical Journal ◽

10.1042/bj2300239 ◽

1985 ◽

Vol 230 (1) ◽

pp. 239-246 ◽

Cited By ~ 17

Author(s):

R A Clegg ◽

I Mullaney

Keyword(s):

Cyclic Amp ◽

Adrenergic Receptors ◽

Phosphodiesterase Inhibitors ◽

Mammary Tissue ◽

Adrenergic Agonists ◽

Pharmacological Agents ◽

Selective Antagonists ◽

Beta 2

The cyclic AMP content of acini, freshly prepared from mammary tissue of lactating rats, was measured during incubation in vitro. Neither adrenergic agonists nor cyclic AMP phosphodiesterase inhibitors alone caused a change of more than 2-fold in the basal cyclic AMP content of acini. Together, however, these agents provoked increases of around 20-fold in acini cyclic AMP content. Forskolin caused similar effects. The relative potency of adrenergic agonists in increasing cyclic AMP in acini, together with the ability of selective antagonists to oppose such rises, indicated that beta 2-adrenergic receptors were involved in mediating the effects. Receptor-binding experiments using [3H]dihydroalprenolol and selective β-antagonists confirmed the predominant presence of beta 2-adrenergic receptors on acini membranes and on membranes prepared from purified mammary secretory epithelial cells. These results elucidate some previous findings [Robson, Clegg & Zammit (1984) Biochem. J. 217, 743-749; Williamson, Munday, Jones, Roberts & Ramsey (1983) Adv. Enzyme Regul. 21, 135-145], questioning the role of cyclic AMP in the regulation of lipogenesis in mammary acini.

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Cytokines in the Control of Beta-2 Microglobulin Release. I. In vitro Studies on Various Haemopoietic Cells

Immunobiology ◽

10.1016/s0171-2985(88)80091-3 ◽

1988 ◽

Vol 177 (1) ◽

pp. 55-65 ◽

Cited By ~ 27

Author(s):

K. Nachbaur ◽

J. Troppmair ◽

P. Bieling ◽

B. Kotlan ◽

P. König ◽

...

Keyword(s):

In Vitro Studies ◽

Beta 2 ◽

Beta 2 Microglobulin ◽

Haemopoietic Cells

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Ligand-dependent occupancy of the retinoic acid receptor beta 2 promoter in vivo

Molecular and Cellular Biology ◽

10.1128/mcb.14.12.8191-8201.1994 ◽

1994 ◽

Vol 14 (12) ◽

pp. 8191-8201

Author(s):

A Dey ◽

S Minucci ◽

K Ozato

Keyword(s):

Retinoic Acid ◽

Dimethyl Sulfate ◽

Dominant Negative ◽

In Vitro Assays ◽

Cell Extracts ◽

Ec Cells ◽

Beta 2 ◽

Responsive Element ◽

Receptor Beta

Retinoic acid (RA) activates transcription of the RA receptor beta 2 (RAR beta 2) gene in embryonal carcinoma (EC) cells. This activation involves binding of the RAR/retinoid X receptor (RAR/RXR) heterodimer to the RA-responsive element (beta RARE). Dimethyl sulfate-based genomic footprinting was performed to examine occupancy of this promoter in P19 EC cells. No footprint was detected at the beta RARE prior to RA treatment, but a footprint was detected within the first hour of RA treatment. Concomitantly, other elements in the promoter, the cyclic AMP-responsive element and tetradecanoyl phorbol acetate-like-responsive element became footprinted. Footprints at these elements were induced by RA without requiring new protein synthesis and remained for the entire duration of RA treatment but rapidly reversed upon withdrawal of RA. A delayed protection observed at the initiator site was also reversed upon RA withdrawal. The RA-inducible footprint was not due to induction of factors that bind to these element, since in vitro assays showed that these factors are present in P19 cell extracts before RA treatment. Significantly, no RA-induced footprint was observed at any of these elements in P19 cells expressing a dominant negative RXR beta, in which RXR heterodimers are unable to bind to the beta RARE. Results indicate that binding of a liganded heterodimer receptor to the beta RARE is the initial event that allows other elements to gain access to the factors. In accordance, reporter analyses showed that a mutation in the beta RARE, but not those in other elements, abrogates RA activation of the promoter. It is likely that the RAR beta 2 promoter opens in a hierarchically ordered manner, signalled by the occupancy of liganded heterodimers.

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A spectrin-like protein from mouse brain membranes: phosphorylation of the 235,000-dalton subunit

AJP Cell Physiology ◽

10.1152/ajpcell.1984.247.1.c61 ◽

1984 ◽

Vol 247 (1) ◽

pp. C61-C73 ◽

Cited By ~ 42

Author(s):

S. R. Goodman ◽

I. S. Zagon ◽

C. F. Whitfield ◽

L. A. Casoria ◽

S. B. Shohet ◽

...

Keyword(s):

Mouse Brain ◽

Beta Subunit ◽

Beta Subunits ◽

Mouse Erythrocyte ◽

Alpha Beta ◽

Beta 2 ◽

Independent Protein ◽

Brain Spectrin

A mouse brain spectrin-like protein, which was an immunoreactive analogue of erythrocyte spectrin, has been isolated from demyelinated membranes. This spectrin analogue was a 10.5 S, 972,000 molecular weight (Mr) (alpha beta)2 tetramer containing subunits of 240,000 (alpha) and 235,000 (beta) Mr. We demonstrated that in vivo only the 235,000 Mr beta subunit of the mouse brain spectrin-like protein was phosphorylated, which was an analogous situation to mouse erythrocyte spectrin in which only the 220,000 Mr beta subunit was phosphorylated. Incubation of isolated membrane fractions with [gamma-32P]ATP +/- adenosine 3',5'-cyclic monophosphate (cAMP) indicated that mouse brain spectrin-like protein, mouse erythrocyte spectrin, and human erythrocyte spectrin's beta subunits were all phosphorylated in vitro by membrane-associated cAMP-independent protein kinases.

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The distribution of beta-1- and beta-2-adrenergic receptors of normal and reeler mouse brain: An in vitro autoradiographic study

Neuroscience ◽

10.1016/0306-4522(87)90283-1 ◽

1987 ◽

Vol 23 (1) ◽

pp. 199-210 ◽

Cited By ~ 16

Author(s):

D. Lorton ◽

J.N. Davis

Keyword(s):

Mouse Brain ◽

Adrenergic Receptors ◽

Autoradiographic Study ◽

Beta 2

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Hemoglobin switching in sheep: characteristics of BFU-E-derived colonies from fetal liver

Blood ◽

10.1182/blood.v56.3.495.bloodjournal563495 ◽

1980 ◽

Vol 56 (3) ◽

pp. 495-500

Author(s):

JE Barker

Keyword(s):

Stem Cells ◽

Fetal Liver ◽

Fetal Hemoglobin ◽

Liver Cells ◽

S Phase ◽

Hemoglobin Switching ◽

Fetal Liver Cells ◽

Beta 2 ◽

Number Of Cells

Two types of erythroid colonies were generated in vitro from sheep fetal liver cells. The first type consisted of single colonies of 8–256 cells that were well hemoglobinized by 4 days; these are thought to originate from CFU-E. The second type consisted of macroscopic colonies composed of several subcolonies that matured between days 3 and 8 in vitro. At maturity, each contained 256 to > 1000 cells that formed a discrete macroscopic cluster. The macroscopic colonies, not previously described in sheep, are thought to be derived from BFU-E. The characteristics of sheep BFU-E were defined and the production of fetal hemoglobin (HbF, alpha 1, gamma 2) and HbC (alpha 2 beta 2) was compared in colonies derived from CFU-E or BFU-E. Bursts developed at erythropoietin (epo) concentrations as low as 0.1 U/ml, although the number observed increased with epo concentration up to 10 U/ml. The number of bursts observed was approximately proportional to the number of cells plated. As shown by thymidine suicide, approximately 50% of both the BFU e and CFU-E were in S-phase when obtained from the fetus. BFU-E were smaller and partially separable from CFU-E after sedimentation at unit gravity. The beta c/gamma synthetic ratio in colonies derived from BFU-E was greater than in CFU-E-derived colonies. These data suggest that the capacity for generation of erythroblasts making HbC is greater in the earlier or more primitive erythroid stem cells in fetal liver.

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