Interaction of thymic peptide thymosin α1 with vasoactive intestinal peptide (VIP) receptors

1986 ◽  
Vol 6 (8) ◽  
pp. 727-733 ◽  
Author(s):  
J. R. Calvo ◽  
R. Goberna ◽  
J. M. Guerrero
Keyword(s):  
Adenylate Cyclase ◽  
Vasoactive Intestinal Peptide ◽  
Plasma Membranes ◽  
Mononuclear Cells ◽  
Specific Binding ◽  
Thymosin Α1 ◽  
Vip Receptors ◽  
Liver Plasma Membranes ◽  
Blood Mononuclear Cells ◽  
Thymic Peptide

Thymic peptide thymosin α1 (10−9 to 3 × 1010−7 M) is shown to inhibit the specific binding of [125I]VIP to rat blood mononuclear cells and liver plasma membranes. Thymosin α1 was 160 and 6250 times less potent that VIP at inhibiting [125I]VIP binding to blood mononuclear cells and liver plasma membranes, respectively. Thymosin α1 (10−10 to 1010−7 M) was weak in stimulating adenylate cyclase activity. Its efficacy is about 25 % and 27 % that of native VIP in blood mononuclear cells and liver plasma membranes, respectively. Thymosin α1 may behave as a partial VIP agonist in rat.

Interaction of a bovine thymic peptide extract with vasoactive intestinal peptide (VIP) receptors

1986 ◽  
Vol 6 (6) ◽  
pp. 579-584
Author(s):  
J. M. Guerrero ◽  
R. Goberna ◽  
P. Molinero ◽  
J. Jimenez ◽  
J. R. Calvo
Keyword(s):  
Adenylate Cyclase ◽  
Plasma Membranes ◽  
Mononuclear Cells ◽  
Weight Basis ◽  
Lymphoid Cells ◽  
Vip Receptors ◽  
Liver Plasma Membranes ◽  
Blood Mononuclear Cells ◽  
Rat Liver Plasma Membranes ◽  
Thymic Peptide

Bovine t hymic peptide extract (1–100 μg/ml) is shown to completely inhibit the binding of [125I]VIP to rat blood mononuclear cells, lymphoid cells of spleen, and liver plasma membranes. In the three models, the bovine thymic peptide extract inhibits [125I]VIP binding with a potency that is 4000–7000 times lower than that of the native VIP, on a weight basis. In rat liver plasma membranes, the bovine thymic peptide extract stimulates adenylate cyclase with a maximal efficiency that is similar to that of VIP. At maximal doses, VIP and thymic peptide extract do not exert an additive effect on adenylate cyclase, suggesting that the activation of the enzyme by the bovine thymic peptide extract occurs through VIP receptors. Finally, no VIP-like immunoreactivity was detected in the thymic peptide extract using an antiserum raised against mammalian VIP. All these data suggest the presence in the bovine thymic peptide extract of a new substance which behaves as a VIP agonist in rat.

scholarly journals Lysophosphatidylcholines can modulate the activity of the glucagon-stimulated adenylate cyclase from rat liver plasma membranes

1979 ◽  
Vol 178 (1) ◽  
pp. 217-221 ◽  
Author(s):  
M D Houslay ◽  
R W Palmer
Keyword(s):  
Adenylate Cyclase ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Hormone Receptors ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Liver Plasma Membranes ◽  
Rat Liver Plasma Membranes ◽  
Increased Sensitivity

1. Synthetic lysophosphatidylcholines inhibit the glucagon-stimulated adenylate cyclase activity of rat liver plasma membranes at concentrations two to five times lower than those needed to inhibit the fluoride-stimulated activity. 2. Specific 125I-labelled glucagon binding to hormone receptors is inhibited at concentrations similar to those inhibiting the fluoride-stimulated activity. 3. At concentrations of lysophosphatidylcholines immediately below those causing inhibition, an activation of adenylate cyclase activity or hormone binding was observed. 4 These effects are essentially reversible. 5. We conclude that the increased sensitivity of glucagon-stimulated adenylate cyclase to inhibition may be due to the lysophosphatidylcholines interfering with the physical coupling between the hormone receptor and catalytic unit of adenylate cyclase. 6. We suggest that, in vivo, it is possible that lysophosphatidylcholines may modulate the activity of adenylate cyclase only when it is in the hormone-stimulated state.

Ontogeny of epidermal growth factor receptor tyrosine kinase in rat liver

1991 ◽  
Vol 260 (2) ◽  
pp. G290-G298 ◽  
Author(s):  
B. K. De ◽  
T. L. Brown ◽  
F. J. Suchy
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Tyrosine Kinase ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Egf Receptor ◽  
Specific Binding ◽  
Liver Plasma Membranes ◽  
Epidermal Growth ◽  
Autokinase Activity

The binding of epidermal growth factor (EGF) to its receptor and the activity of the receptor intrinsic protein-tyrosine kinase were studied during the ontogeny of rat liver. The number of EGF receptors during pre- and postnatal development was first compared in crude liver plasma membranes using 1) specific binding of 125I-labeled EGF and 2) immunoblot analysis using any antireceptor polyclonal rabbit antibody. Both methods detected the expression of the EGF receptor in fetal rat liver on day 17 of gestation, but in an amount markedly less than the adult. Within 24 h, there was a more than twofold increase in EGF binding to plasma membranes as well as a marked increase in receptor immunoreactivity. However, after birth, there was a precipitous drop in receptor number to less than 20% of the adult level by the end of the first postnatal day (P less than 0.001). Next, the presence of EGF-stimulated tyrosine kinase activity (autophosphorylation) was determined during the same stages of development. Electrophoresis of membranes phosphorylated in the presence or absence of EGF followed by autoradiography demonstrated autokinase activity stimulated by EGF in day 18 and 19 fetal liver plasma membranes, but not in membranes on day 17 of gestation. Similar to the pattern observed with EGF binding, there was a decrease in autokinase activity in early neonatal plasma membranes followed by an increase to near adult levels by 7 days postnatally. Quantitation of the amount of 32P radioactivity associated with the EGF receptor bands in each age group, correlated with the degree of autophosphorylation assessed by autoradiography.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Elevated membrane cholesterol concentrations inhibit glucagon-stimulated adenylate cyclase

1983 ◽  
Vol 210 (2) ◽  
pp. 437-449 ◽  
Author(s):  
A D Whetton ◽  
L M Gordon ◽  
M D Houslay
Keyword(s):  
Fatty Acid ◽  
Adenylate Cyclase ◽  
Spin Probe ◽  
Plasma Membranes ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Cholesterol Concentration ◽  
Lipid Phase ◽  
Lipid Order ◽  
Liver Plasma Membranes

A method was devised which increases the cholesterol concentration of rat liver plasma membranes by exchange from cholesterol-rich liposomes at low temperature (4 degrees C). When the cholesterol concentration of liver plasma membranes is increased, there is an increase in lipid order as detected by a decrease in mobility of an incorporated fatty acid spin probe. This is accompanied by an inhibition of adenylate cyclase activity. The various ligand-stimulated adenylate cyclase activities exhibit different sensitivities to inhibition by cholesterol, with inhibition of glucagon-stimulated greater than fluoride-stimulated greater than basal activity. The bilayer-fluidizing agent benzyl alcohol is able to reverse the inhibitory effect of cholesterol on adenylate cyclase activity in full. The thermostability of fluoride-stimulated cyclase is increased in the cholesterol-rich membranes. Elevated cholesterol concentrations abolish the lipid-phase separation occurring at 28 degrees C in native membranes as detected by an incorporated fatty acid spin probe. This causes Arrhenius plots of glucagon-stimulated adenylate cyclase activity to become linear, rather than exhibiting a break at 28 degrees C. It is suggested that the cholesterol contents of both halves of the bilayer are increased by the method used and that inhibition of adenylate cyclase ensues, owing to the increase in lipid order and promotion of protein-protein and specific cholesterol-phospholipid interactions.

Ontogeny of hepatic insulin and glucagon receptors and adenylate cyclase in rabbit

1983 ◽  
Vol 244 (6) ◽  
pp. E624-E631
Author(s):  
S. Ganguli ◽  
M. K. Sinha ◽  
B. Sterman ◽  
P. Harris ◽  
M. A. Sperling
Keyword(s):  
Adenylate Cyclase ◽  
Cholera Toxin ◽  
Plasma Membranes ◽  
Specific Binding ◽  
Regulatory Protein ◽  
Late Gestation ◽  
Camp Production ◽  
Hormonal Activation ◽  
Glucagon Receptors ◽  
Significant Increment

In rabbit liver plasma membranes (LPM), specific binding of 125I-insulin rapidly increased in late gestation and peaked at birth, declining thereafter. In contrast, 125I-glucagon binding was lowest in late gestation, somewhat higher at birth, and increased by 48 h although only to 20-25% of adult. These changes in binding were due to changing numbers of receptors involving predominantly high affinity sites for insulin and low affinity sites for glucagon, with only minor changes in affinity. Despite measurable glucagon receptors by birth, fetal LPM produced no increment above basal in cAMP production with maximal doses of glucagon (10(-6) M), prostaglandin E1 (10(-4) M), or epinephrine (10(-4) M). Near birth only NaF (10 mM) produced a modest but significant increment in cAMP. By 2 h postbirth, all stimuli evoked significant increments in cAMP production that increased progressively but was still only 15-20% of adult at 48 h. Furthermore, although specific binding of cholera toxin was greater in fetal LPM (11 +/- 1 vs. 6 +/- 1%), cholera toxin-stimulated cAMP production increased by only 12-26% above basal in the fetus compared with 220% in adult. Markers of membrane purity including 5'-nucleotidase, phosphodiesterase, and insulin or glucagon degradation were not different in fetus and adult. We conclude that receptors and components of the adenylate cyclase complex mature independently; initial coupling occurs between the G/F regulatory protein and the catalytic unit (NaF but not hormonal activation) followed within hours of birth by coupling to the hormone receptor.

Effects of 4-hydroxynonenal on adenylate cyclase and 5′-nucleotidase activities in rat liver plasma membranes

1985 ◽  
Vol 53 ◽  
pp. 209-217 ◽  
Author(s):  
Luciana Paradisi ◽  
Carla Panagini ◽  
Maurizio Parola ◽  
Giuseppina Barrera ◽  
Mario U. Dianzani
Keyword(s):  
Adenylate Cyclase ◽  
Rat Liver ◽  
Plasma Membranes ◽  
Liver Plasma Membranes ◽  
Rat Liver Plasma Membranes
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