Uncoupling of Lipolysis from Cyclic AMP by Procaine: a Tool for Studying the Mechanism of Action of Antilipolytic Agents

1975 ◽  
Vol 53 (4) ◽  
pp. 603-609 ◽  
Author(s):  
Mario D'Costa ◽  
Aubie Angel
Keyword(s):  
Adipose Tissue ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Mechanism Of Action ◽  
Initial Rate ◽  
Direct Action ◽  
Inhibitory Effect ◽  
Glycerol Release ◽  
Cyclic Amp Accumulation ◽  
Low K

The initial rate of net glycerol release in norepinephrine-stimulated adipose tissue fragments was inhibited (40–78%) by procaine–HCl (1–5 mM), whereas basal (unstimulated) lipolysis was unaffected. A dose-related inhibition of norepinephrine-induced lipolysis by procaine–HCl (0.1–1 mM) also occurred in adipocytes. Procaine-induced antilipolysis was associated with an augmented rather than a reduced hormone-stimulated increment in intracellular cyclic AMP. The dissociation of lipolysis from cyclic AMP accumulation has been termed the uncoupling effect of procaine. This effect of procaine was employed to define the precise mechanism of action of the antilipolytic drug clofibrate (Atromid-S®) which inhibits lipolysis by reducing cyclic AMP. A reduction in cyclic AMP by clofibrate was demonstrated in norepinephrine-stimulated cells exposed to procaine (uncoupled system). Thus, the inhibitory effect of clofibrate on cyclic AMP could not be attributed to accumulation of products of lipolysis. Because neither procaine–HCl nor clofibrate had any effect on the low Km 3′:5′-cyclic-AMP phosphodiesterase (EC 3.1.4.17) activity in hormone stimulated cells, the clofibrate-induced reduction in cyclic AMP was attributed to its direct action on adipocyte adenylate cyclase.

scholarly journals Studies on the Mechanism of Action of the Inhibitory Effect of Prostaglandin F2α on Cyclic AMP Accumulation in Rat Corpora Lutea of Various Ages1

1979 ◽  
Vol 21 (5) ◽  
pp. 1175-1183 ◽  
Author(s):  
M. Iqbal Khan ◽  
Sten Rosberg ◽  
Michal Lahav ◽  
Sergio A. Lamprecht ◽  
Gunnar Selstam ◽  
...  
Keyword(s):  
Cyclic Amp ◽  
Mechanism Of Action ◽  
Prostaglandin F2α ◽  
Inhibitory Effect ◽  
Corpora Lutea ◽  
Cyclic Amp Accumulation

scholarly journals Attenuated adenosine-sensitivity and decreased adenosine-receptor number in adipocyte plasma membranes in human obesity

1991 ◽  
Vol 279 (1) ◽  
pp. 17-22 ◽  
Author(s):  
J M Kaartinen ◽  
S P Hreniuk ◽  
L F Martin ◽  
S Ranta ◽  
K F LaNoue ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Adenosine Receptors ◽  
Plasma Membranes ◽  
Normal Weight ◽  
Fat Cells ◽  
Cyclic Amp Accumulation ◽  
Obese Subjects ◽  
Receptor Number

Fat-cells were isolated from patients of body-mass indices (BMIs) ranging from 17.9 to 83.9 kg/m2. Isoprenaline-stimulated cyclic AMP accumulation in cells prepared from obese subjects as compared with normal-weight subjects, was less sensitive to inhibition by the adenosine agonist N6-(phenylisopropyl)adenosine (PIA) (P = 0.047). The inhibition of 7 beta-desacetyl-7 beta-[gamma-(N-methylpiperazino) butyryl]-forskolin-stimulated adenylate cyclase by PIA in the presence of adenosine deaminase was also much attenuated in crude plasma membranes of adipocytes prepared from massively obese patients as compared with lean controls (P = 0.0143). This difference was probably not due to different cell size, because adenylate cyclase of crude plasma membranes of large adipocytes was actually more sensitive to PIA than was adenylate cyclase of membranes of smaller fat-cells co-isolated from the same individual. The stimulatory effect of PIA on glucose uptake in the presence of adenosine deaminase was depressed in adipocytes prepared from obese subjects and correlated with BMI at r = -0.626 (P = 0.007) at 100 nM-PIA. The adenosine receptors were studied by using the adenosine antagonist 1,3-[3H]dipropyl-8-cyclopentylxanthine. The binding was rapid and proportional to protein concentration. There was no difference in the affinities of receptors in membranes of obese and normal-weight subjects; Kd values of all patients averaged 3.3 nM. Bmax values were 54 and 130 fmol/mg of protein in membranes prepared from seven obese and five control patients respectively. The Bmax values calculated per mg of protein correlated with BMI at r = -0.539 (P = 0.047). The adenosine content of adipose tissue was higher in obese than in control subjects. These results demonstrate an attenuated response of cyclic AMP accumulation, adenylate cyclase and glucose uptake to adenosine in fat-cells prepared from obese subjects, and suggest that this change is at least partly due to changes in the amount of adenosine receptors, but not their affinity. The decreased receptor number could be due to higher adenosine content. A higher adenosine concentration in adipose tissue could explain why lipolysis is inhibited in situ in obesity, and the desensitization could explain the diminished response to adenosine analogues in isolated fat-cells.

Use of pertussis toxin to investigate the mechanism of action of prostaglandin F2α on the corpus luteum in sheep

1993 ◽  
Vol 10 (1) ◽  
pp. 79-85 ◽  
Author(s):  
T J McCann ◽  
A P F Flint
Keyword(s):  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Corpus Luteum ◽  
G Protein ◽  
Mechanism Of Action ◽  
Pertussis Toxin ◽  
Prostaglandin F2α ◽  
Inhibitory Effect ◽  
Luteal Tissue ◽  
Hydrolysis Of

ABSTRACT Pertussis toxin catalysed the ADP-ribosylation of a protein of Mr 40 000 in ovine luteal tissue. Ribosylation of 45% of this protein in whole cell incubations (as judged by subsequent ribosylation of cell-free preparations in the presence of [32P]NAD) attenuated the prostaglandin (PG)F2α-stimulated hydrolysis of [3H]inositol-labelled phosphatidylinositol-4,5-bisphosphate into inositol trisphosphate by 60%, but did not affect the inhibition by PGF2α of LH-stimulated accumulation of cyclic AMP. It is concluded that activation of phospholipase C by PGF2α involves a pertussis toxin-sensitive protein, probably a G protein, and that the inhibitory effect of PGF2α on LH-stimulated adenylate cyclase is unlikely to be directly mediated by such a protein.

Increased response of adipose tissue of the ob/ob mouse to the action of adrenaline after treatment with thyroxin

1977 ◽  
Vol 55 (6) ◽  
pp. 1320-1329 ◽  
Author(s):  
N. Bégin-Heick ◽  
H. M. C. Heick
Keyword(s):  
Fatty Acids ◽  
Adipose Tissue ◽  
Fatty Acid ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Epididymal Adipose Tissue ◽  
Lipolytic System ◽  
Low K ◽  
Fatty Acid Mobilization

The activity of the lipolytic system of the obese hyperglycemic mouse was assessed after treatment with physiological doses of thyroxin (T4). The treatment significantly increased fatty acid mobilization in response to adrenaline over the levels observed in the control mice under all conditions studied. The activities of the high- and low-Km phosphodiesterases and of adenylate cyclase were also studied. Treatment of the ob/ob mice with T4 had little effect on the activities of the cyclic AMP phosphodiesterases (high and low Km) but it partially restored the activity of adenylate cyclase, which is deficient in these animals. A correlation was found in the T4-treated obese animals between the ability of the epididymal adipose tissue to mobilize fatty acids, its ability to increase the intracellular levels of cyclic AMP, and the activity of adenylate cyclase in response to adrenaline stimulation.

Induction And Potentiation Of Platelet Aggregation By Clonidine And 7ρ-Aminoclonidine, Partial Agonists Of The α2-Receptor Which Regulates Platelet Adenylate Cyclase

1981 ◽  
Author(s):  
David C Stump ◽  
Donald E Macfarlane
Keyword(s):  
Platelet Aggregation ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Specific Binding ◽  
Phase 1 ◽  
Intrinsic Activity ◽  
Second Phase ◽  
Adrenergic Agents ◽  
Cyclic Amp Accumulation ◽  
Induced Aggregation

Epinephrine induces platelet aggregation, potentiates aggregation by other agents, and blocks the stimulation of the adenylate cyclase by prostaglandins. Synthetic α-adrenergic agents have not been shown to induce aggregation. The effects of clonidine, an α2-agonist, and ρ-aminoclonidine on platelets were examined. Clonidine potentiated aggregation induced by 0.5μM ADP by 1.4-fold (1/2 max 0.5μM). It did not induce significant aggregation itself, and it inhibited aggregation induced by 5μM epinephrine (1/2 max lμM). It inhibited cyclic AMP accumulation induced by PGE1 by a maximum of 25% (1/2 max O.lμM) and it blocked inhibition by epinephrine. No significant specific binding of [3H] clonidine was observed to intact platelets. ρ-Aminoclonidine induced aggregation with delayed second phase (1/2 max 0.2μM), and potentiated ADP aggregation by 2-fold (1/2 max 0.2μM). Aggregation induced by epinephrine was more rapid, and was partially inhibited by ρ-aminoclonidine. It inhibited cyclic AMP accumulation by 50% max (1/2 max O.lμM) and attenuated epinephrine’s effect to the same level. The direct effects of ρ-aminoclonidine were blocked by lμM yohimbine, a selective α2-antagonist. Both clonidine and ρ—aminoclonidine blocked the specific binding of [3H]yohimbine (1/2 max 0.5μM). These results suggest that the platelet bears an α2-receptor with affinity for epinephrine, ρ-aminoclonidine and clonidine as agonists but that these agents display differing intrinsic activity and/or receptor reserve.

scholarly journals Oscillations of cyclic nucleotide concentrations in relation to the excitability of Dictyostelium cells

1979 ◽  
Vol 81 (1) ◽  
pp. 33-47 ◽  
Author(s):  
G. Gerisch ◽  
D. Malchow ◽  
W. Roos ◽  
U. Wick
Keyword(s):  
Signal Processing ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Inhibitory Effect ◽  
Camp Concentration ◽  
Surface Receptors ◽  
Camp Generation ◽  
Adenylate Cyclase Activation ◽  
Signal Input ◽  
Extracellular Camp

Aggregating cells of Dictyostelium discoideum are able to release cyclic AMP periodically. The oscillations of cAMP generation are associated with changes in adenylate cyclase activity. Cyclic AMP receptors on the cell surface are functionally coupled to the oscillating system as evidenced by phase shifts that are induced by small pulses of extracellular cAMP. An important element of the oscillating system is the signal processing from surface receptors to the adenylate cyclase. This pathway exhibits adaptation resulting in the suppression of responses to constant, elevated concentrations of cAMP. The signal input for adenylate cyclase activation is, therefore, a change in the extracellular cAMP concentration with time. Oscillations in the absence of detectable changes of intra- or extracellular cAMP concentrations suggest the possibility that there is a metabolic network in D. discoideum cells that undergoes oscillations without coupling to adenylate cyclase. Cyclic GMP concentrations oscillate with a slight phase difference in advance of that of cAMP, suggesting that the two nucleotide cyclases might not be activated by the same mechanism. Elevation of extracellular calcium exerts an inhibitory effect on the accumulation of cAMP and on the second of the two cGMP peaks.

scholarly journals Bradykinin-dependent activation of adenylate cyclase activity and cyclic AMP accumulation in tracheal smooth muscle occurs via protein kinase C-dependent and -independent pathways

1994 ◽  
Vol 297 (1) ◽  
pp. 233-239 ◽  
Author(s):  
P A Stevens ◽  
S Pyne ◽  
M Grady ◽  
N J Pyne
Keyword(s):  
Smooth Muscle ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Cholera Toxin ◽  
Phospholipase D ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Tracheal Smooth Muscle ◽  
Constitutive Activation ◽  
Cyclic Amp Accumulation

Treatment of cultured tracheal smooth-muscle cells (TSM) with phorbol 12-myristate 13-acetate (PMA) (100 nM) or bradykinin (100 nM) elicited enhanced basal and guanosine 5′-[beta gamma-imido]-triphosphate-stimulated adenylate cyclase activities in subsequently isolated membranes. Combined stimulation of cells was non-additive, indicating that both agents activate adenylate cyclase via similar routes. Both PMA (100 nM) and bradykinin (100 nM) allowed the alpha subunit of Gs to act as a more favourable substrate for its cholera-toxin-catalysed ADP-ribosylation in vitro. PMA was without effect on intracellular cyclic AMP in control cells. However, constitutive activation of Gs by treatment in vivo with cholera toxin (0.5 ng/ml, 18 h) sensitized the cells to PMA stimulation, resulting in a concentration-dependent increase in intracellular cyclic AMP accumulation (EC50 = 7.3 +/- 2.5 nM, n = 5). Bradykinin also elicited a concentration-dependent increase in intracellular cyclic AMP (EC50 = 63.3 +/- 14.5 nM, n = 3). Constitutive activation of Gs resulted in an increased maximal response (10-fold) and potency (EC50 = 6.17 +/- 1.6 nM, n = 3) to bradykinin. This response was not affected by the B2-receptor antagonist, NPC567 [which selectively blocks bradykinin-stimulated phospholipase C (PLC), with minor activity against phospholipase D (PLD) activity]. Des-Arg9-bradykinin (a B1-receptor agonist) was without activity. These results suggest that the receptor sub-type capable of activating PLD may also be stimulatory for cyclic AMP accumulation. Furthermore, pre-treatment of the cells with butan-l-ol (0.3%, v/v), which traps phosphatidate derived from PLD reactions, blocked the bradykinin-stimulated increase in intracellular cyclic AMP. These studies suggest that there may be a causal link between PLD-derived phosphatidate and the positive modulation of adenylate cyclase activity. In support of this, the concentration-dependence for bradykinin-stimulated adenylate cyclase activity was identical with that of bradykinin-stimulated phospholipase D activity (EC50 = 5 nM). Bradykinin, but not PMA, was also capable of eliciting the inhibition of cyclic AMP phosphodiesterase activity in TSM cells (EC50 > 100 nM) via an unidentified mechanism. These studies indicate that cross-regulation between the cyclic AMP pathway and phospholipid-derived second messengers in TSM cells does not occur as a consequence of PLC-catalysed PtdIns(4,5)P2 hydrolysis, but may involve, in part, PLD-catalysed phosphatidylcholine hydrolysis.

Importance of the Cyclic AMP Concentration for the Rate of Lipolysis in Human Adipose Tissue

1980 ◽  
Vol 59 (3) ◽  
pp. 199-201 ◽  
Author(s):  
P. Arner ◽  
J. Östman
Keyword(s):  
Adipose Tissue ◽  
Cyclic Amp ◽  
Subcutaneous Adipose Tissue ◽  
Human Adipose Tissue ◽  
Strong Positive Correlation ◽  
Glycerol Release ◽  
Two Parameters ◽  
Subcutaneous Adipose ◽  
The Relationship ◽  
Release Of Glycerol

1. The activation of lipolysis on incubation of human subcutaneous adipose tissue was examined in terms of the relationship between the release of glycerol and the concentration of tissue cyclic AMP. 2. A strong positive correlation was obtained between the maximum concentration of cyclic AMP and the rate of glycerol release in the presence of noradrenaline (r = 0.9), whereas, in the basal state, these two parameters were only weakly correlated (r = 0.45). 3. It appears that the noradrenaline-induced rate of lipolysis depends upon the maximal concentration of cyclic AMP that is present in human adipose tissue.

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