scholarly journals Comparison of the effects of insulin and adrenergic agonists on the phosphorylation of an acid-soluble 22 kDa protein in rat epididymal fat-pads and isolated fat-cells

1992 ◽  
Vol 282 (3) ◽  
pp. 729-736 ◽  
Author(s):  
T A Diggle ◽  
R M Denton
Keyword(s):  
Cyclic Amp ◽  
Phorbol Esters ◽  
Protein Composition ◽  
Fat Cells ◽  
Adrenergic Agonists ◽  
Beta Adrenergic ◽  
Epididymal Fat ◽  
Apparent Homogeneity ◽  
Sds Page ◽  
Fat Pads

1. Earlier studies have shown that exposure of fat-cells to insulin results in the rapid increased phosphorylation of an acid-soluble 22 kDa protein and that increases in phosphorylation were also evident in cells exposed to adrenaline [Belsham & Denton (1980) Biochem. Soc. Trans. 8, 382-383; Belsham, Brownsey, Hughes & Denton (1980) Diabetologia 18, 307-312]. 2. The effects of adrenaline are shown to be brought about through beta-adrenergic receptors and to be mimicked by other agents which increase cell cyclic AMP concentrations. The maximum extent of phosphorylation is about 60% of that observed with insulin. Increased phosphorylation is also observed in fat-cells exposed to vasopressin, oxytocin and phorbol esters, but not to alpha-adrenergic agonists. 3. No changes in the phosphorylation of the protein are evident in epididymal fat-pads from fat-fed, starved or starved/refed animals, despite the large changes in protein composition of fat-cells which accompany these nutritional alterations. This suggests that the protein is not closely involved in lipogenesis or associated metabolic pathways, but rather that it may play a more general regulatory role. 4. The 22 kDa protein migrates as a doublet on SDS/PAGE even after purification to apparent homogeneity by sequential use of Mono Q chromatography, SDS/PAGE and h.p.l.c. The amino acid compositions of the two components are very similar and share features in common with a number of proteins, including inhibitor-1, inhibitor-2, dopamine- and cyclic-AMP-regulated phosphoprotein (DARPP-32), and G-substrate, which may be involved in the regulation of protein phosphatase activity. 5. Phosphopeptide mapping and phosphoamino acid analysis reveals that insulin increases the phosphorylation of two distinct peptides within the protein (in one peptide insulin increases the amount of phosphothreonine, whereas in the other the hormone increases the amounts of phosphothreonine and phosphoserine). Both components of the doublet exhibit similar changes in phosphorylation, and hence the differences in migration are not the result of differences in phosphorylation, as suggested previously [Blackshear, Nemenoff & Avruch (1983) Biochem. J. 214, 11-19]. The pattern of phosphorylation observed with the beta-adrenergic agonist isoprenaline was similar to that observed with insulin. 6. The possible role and regulation of the 22 kDa protein are discussed.

The inhibitory effects of some adenosine nucleolipids on the lipolysis in rat epididymal fat pads in vitro

1979 ◽  
Vol 44 (5) ◽  
pp. 1651-1656 ◽  
Author(s):  
Sixtus Hynie ◽  
Jiří Smrt
Keyword(s):  
Fatty Acids ◽  
Cyclic Amp ◽  
Dibutyryl Cyclic Amp ◽  
Inhibitory Effects ◽  
Epididymal Fat ◽  
Fat Pads

3'-Oleolyl-2,3-dihydroxypropyl-AMP, 3'-stearoyl-2,3-dihydroxypropyl-AMP, octadecyl-AMP and palmitamidoethyl-AMP inhibited in comparison with adenosine or fatty acids much stronger the lipolysis in rat epididymal fat pads in vitro stimulated by isoproterenol, theophylline and dibutyryl cyclic AMP. The inhibition of the effects of the two latter drugs suggest that the described effect is caused not only by the inhibition of the cyclic AMP production but also by the inhibition of its effect on the following steps in process of lipolysis.

Interaction between the antidepressant-like behavioral effects of beta adrenergic agonists and the cyclic AMP PDE inhibitor rolipram in rats

2005 ◽  
Vol 182 (1) ◽  
pp. 104-115 ◽  
Author(s):  
Han-Ting Zhang ◽  
Ying Huang ◽  
Kathleen Mishler ◽  
Sandra C. Roerig ◽  
James M. O'Donnell
Keyword(s):  
Cyclic Amp ◽  
Behavioral Effects ◽  
Adrenergic Agonists ◽  
Beta Adrenergic ◽  
Beta Adrenergic Agonists

scholarly journals The effect of β-adrenergic agonists on the membrane potential of fat-cell mitochondria in situ

1982 ◽  
Vol 206 (3) ◽  
pp. 611-618 ◽  
Author(s):  
R J Davis ◽  
B R Martin
Keyword(s):  
Membrane Potential ◽  
Fat Cells ◽  
Adrenergic Agonists ◽  
Fat Cell ◽  
Beta Adrenergic ◽  
Fatty Acid Binding ◽  
Beta Adrenergic Agonists ◽  
Adrenergic Antagonist ◽  
Beta Adrenergic Agonist

1. The accumulation of [3H]methyltriphenylphosphonium by isolated fat-cells was used to estimate the membrane potential of mitochondria in situ. 2. Adrenaline caused a large decrease in the accumulation of [3H]methyltriphenylphosphonium. Mitochondria in fat-cells incubated in the presence of adrenaline had a very low calculated membrane potential. This effect was also given by isoprenaline (a beta-adrenergic agonist) and was blocked by propranolol (a beta-adrenergic antagonist). 3. The effect of isoprenaline could be partially antagonized by the use of media with high albumin concentrations. Addition of sodium oleate to saturate the fatty acid-binding sites on the albumin reversed this antagonism. 4. It is proposed that the decrease in the calculated mitochondrial membrane potential is due to the uncoupling effect of the non-esterified fatty acids released by the stimulation of lipolysis observed in the presence of beta-adrenergic agonists.

scholarly journals Inhibition by calcium ions of adenosine cyclic monophosphate formation in sealed pigeon erythrocyte ‘ghosts’. A study using the photoprotein obelin

1978 ◽  
Vol 176 (1) ◽  
pp. 53-66 ◽  
Author(s):  
A K Campbell ◽  
R L Dormer
Keyword(s):  
Cyclic Amp ◽  
Initial Rate ◽  
Ionophore A23187 ◽  
Erythrocyte Ghosts ◽  
Adrenergic Agonists ◽  
Intact Cells ◽  
Beta Adrenergic ◽  
Beta Adrenergic Agonists ◽  
The Relationship ◽  
Stimulation Of

1. Sealed pigeon erythrocyte ‘ghosts’ were prepared containing ATP and the Ca2+-activated photoprotein obelin to investigate the relationship cyclic AMP formation and internal free Ca2+. 2. The ‘ghosts’ were characterized by (a) morphology (optical and electron microscopy), (b) composition (haemoglobin, K+, Na+, Mg2+, ATP, obelin), (c) permeability to Ca2+, assessed by obelin luminescence and (d) hormone sensitivity (the effect of beta-adrenergic agonists and antagonists on cyclic AMP formation). 3. The effect of osmolarity at haemolysis and ATP at resealing on these parameters was investigated. 4. Sealed ‘ghosts’, containing approx. 2% of original haemoglobin, 150mM-K+, 0.5MM-ATP, 10(3)–10(4) obelin luminescence counts/10(6) ‘ghosts’, which were relatively impermeable to Ca2+ and in which cyclic AMP formation was stimulated by beta-adrenergic agonists over a concentration range similar to that for intact cells, could be prepared after haemolysis in 6mM-NaCl3mM-MgCl2/50mM-Tes, pH7, and resealing for 30min at 37 degrees C in the presence of ATP and 150mM-KCl. 5. The initial rate of adrenaline-stimulated cyclic AMP formation in these ‘ghosts’ was 30–50% of that in intact cells and was inhibited by the addition of extracellular Ca2+. Addition of Ca2+ to the ‘ghosts’ resulted in a stimulation of obelin luminescence, indicating an increase in internal free Ca2+ under these conditions. 6. The ionophore A23187 increased the rate of obelin luminescence in the ‘ghosts’ and also inhibited the adrenaline-stimulated increase in cyclic AMP. 7. The effect of ionophore A23187 on obelin luminescence and on cyclic AMP formation in the ‘ghosts’ was markedly decreased by sealing EGTA inside the ‘ghosts’. 8. It was concluded that cyclic AMP formation inside sealed pigeon erythrocyte ‘ghosts’ could be inhibited by more than 50% by free Ca2+ concentrations in the range 1–10 micrometer.

scholarly journals The activation of Na+-dependent efflux of Ca2+ from liver mitochondria by glucagon and β-adrenergic agonists

1983 ◽  
Vol 210 (2) ◽  
pp. 463-472 ◽  
Author(s):  
T P Goldstone ◽  
R J Duddridge ◽  
M Crompton
Keyword(s):  
Cyclic Amp ◽  
Liver Mitochondria ◽  
Ionophore A23187 ◽  
Adrenergic Agonists ◽  
Adrenergic Agonist ◽  
Perfusion Medium ◽  
Beta Adrenergic ◽  
Beta Adrenergic Agonist

The Na+-induced efflux of Ca2+ from liver mitochondria was activated by tissue pretreatment with 1 microM-adrenaline, 1 microM-isoprenaline, 10 nM-glucagon and 100 microM-cyclic AMP when 10 mM-lactate plus 1 mM-pyruvate were present in the perfusion medium. Infusion of the alpha 1-adrenergic agonist, phenylephrine (10 microM), was ineffective. The activation induced by the beta-adrenergic agonist, isoprenaline, was maximal after infusion of agonist for 2 min. The isoprenaline-induced activation was very marked (120-220%), with about 7 nmol of intramitochondrial Ca2+/mg of protein, but was not evident with greater than 15 nmol of Ca2+/mg. Ca2+ efflux in the absence of Na+ and in the presence of the Ca2+ ionophore A23187 was not affected by isoprenaline pretreatment over the range 6-23 nmol of internal Ca2+/mg. With 10 mM-lactate plus 1 mM-pyruvate in the perfusion medium, glucagon and isoprenaline infusion increased tissue cyclic AMP content about 8-fold and 3-fold respectively. With 10 mM-pyruvate alone, neither glucagon nor isoprenaline caused a significant increase in cyclic AMP. Omission of lactate also abolished the ability of glucagon, but not of isoprenaline, to activate the Na+-induced efflux of Ca2+. The data indicate that cyclic AMP may mediate the activation caused by glucagon, but provide no evidence that cyclic AMP is an obligatory link in the beta-adrenergic-induced activation.

Sign in / Sign up

Export Citation Format

Share Document