Cyclic AMP enhances the vasopressin-mediated stimulation of inositol phosphate production in cultured rat hepatocytes

1989 ◽  
Vol 17 (1) ◽  
pp. 90-91
Author(s):  
RICHARD A. PITTNER ◽  
JOHN N. FAIN
Keyword(s):  
Cyclic Amp ◽  
Inositol Phosphate ◽  
Rat Hepatocytes ◽  
Inositol Phosphate Production ◽  
Cultured Rat Hepatocytes ◽  
Stimulation Of

scholarly journals Exposure of cultured hepatocytes to cyclic AMP enhances the vasopressin-mediated stimulation of inositol phosphate production

1989 ◽  
Vol 257 (2) ◽  
pp. 455-460 ◽  
Author(s):  
R A Pittner ◽  
J N Fain
Keyword(s):  
Cyclic Amp ◽  
Inositol Phosphate ◽  
Rat Hepatocytes ◽  
Isolated Rat Hepatocytes ◽  
Phosphate Accumulation ◽  
Primary Monolayer Culture ◽  
Inositol Phosphate Production ◽  
Inositol Phosphate Accumulation ◽  
Primary Monolayer ◽  
Stimulation Of

Isolated rat hepatocytes in primary monolayer culture were maintained for 18-24 h in the presence of 10% (v/v) serum and [3H]inositol. Vasopressin (100 nM) stimulated the production of inositol mono-, bis- and tris-phosphates (IP1, IP2, and IP3). Prior exposure of hepatocytes to 8-bromo cyclic AMP (8Br-cAMP; 100 microM), but not 8-bromo cyclic GMP, enhanced the vasopressin-mediated stimulation of inositol phosphate accumulation, but had no significant effect on their formation in the absence of vasopressin. The effect of the cyclic AMP analogue was mimicked by glucagon (10 nM), and was seen whether cyclic AMP or glucagon was added 5 min or 12 h before the addition of vasopressin. An 8 h incubation with dexamethasone (100 nM) enhanced the accumulation of IP3, but not that of IP2 or IP1, in the presence of 8Br-cAMP and vasopressin. Cycloheximide or actinomycin D had little effect on the vasopressin stimulation of inositol phosphate accumulation, after an 8 h incubation in the presence or absence of 8Br-cAMP.

scholarly journals Divergent roles for ferric ions in the biological activity of amidated and non-amidated gastrins

2004 ◽  
Vol 181 (2) ◽  
pp. 315-325 ◽  
Author(s):  
J Pannequin ◽  
JP Tantiongco ◽  
S Kovac ◽  
A Shulkes ◽  
GS Baldwin
Keyword(s):  
Biological Activity ◽  
Inositol Phosphate ◽  
Peptide Hormone ◽  
Iron Chelator ◽  
Spectroscopic Studies ◽  
Jurkat Cells ◽  
Ferric Ion ◽  
Ferric Ions ◽  
Inositol Phosphate Production ◽  
Stimulation Of

Amidated forms of the peptide hormone gastrin act via the cholecystokinin-2 receptor to stimulate gastric acid secretion, whereas non-amidated forms stimulate colonic mucosal proliferation via a novel, as yet uncharacterised, receptor. Nuclear magnetic resonance (NMR) and fluorescence spectroscopic studies have revealed that glycine-extended gastrin17 bound two ferric ions, and that ferric ion binding was essential for biological activity. We have therefore investigated the role of ferric ions in the biological activity of amidated gastrin17. As with glycine-extended gastrin17, fluorescence quenching experiments indicated that Glu7 Ala and Glu8,9 Ala mutants of amidated gastrin17 each bound only one ferric ion. The affinity of the mutant peptides for the cholecystokinin-2 receptor on transfected COS-7 cells or on Tlymphoblastoid Jurkat cells, and their potency in stimulation of proliferation in Jurkat cells and inositol phosphate production in transfected COS-7 cells, were similar to the values obtained for amidated gastrin17. In addition, the iron chelator desferrioxamine did not significantly inhibit either binding of amidated gastrin17 to the cholecystokinin-2 receptor, or stimulation of inositol phosphate production by amidated gastrin17 in transfected COS-7 cells. We conclude that, in contrast to glycine-extended gastrin17, binding of ferric ions is not essential for the biological activity of amidated gastrin17. Our results support the concept of distinct modes of action for amidated and non-amidated gastrins, and raise the possibility of developing selective antagonists of the actions of non-amidated and amidated gastrins.

scholarly journals Stimulation by glucocorticoids of protein degradation in hepatocyte monolayers

1981 ◽  
Vol 196 (1) ◽  
pp. 33-40 ◽  
Author(s):  
M F Hopgood ◽  
M G Clark ◽  
F J Ballard
Keyword(s):  
Cyclic Amp ◽  
Protein Degradation ◽  
Monolayer Culture ◽  
Rat Hepatocytes ◽  
Protein Breakdown ◽  
Dibutyryl Cyclic Amp ◽  
Intracellular Proteins ◽  
Autophagic Process ◽  
Soluble Material ◽  
Stimulation Of

1. Protein degradation in rat hepatocytes in stationary monolayer culture was measured as release of radioactive trichloroacetic acid-soluble material from intracellular proteins labelled with [3H]leucine. 2. Glucocorticoids, but not other steroids, stimulated protein breakdown in the hepatocyte monolayers. The effects observed were greater when the cells were preincubated with the hormones, indicating that the stimulation was not immediate. In addition, the stimulation by glucocorticoids persisted for up to 4 h after hormone removal. 3. Cycloheximide and the lysosomotropic agents leupeptin and ammonia effectively blocked glucocorticoid stimulation of protein degradation. 4. Insulin blocked dexamethasone stimulation when added at the same time as the steroid, but not when added 3 h later. 5. Stimulation of protein breakdown by dexamethasone was additive with that by glucagon or dibutyryl cyclic AMP, suggesting that its mechanism of action is different from that of the latter two agents. 6. Total activities of several lysosomal enzymes were unaffected under conditions where protein breakdown was stimulated by either glucagon or dexamethasone. 7. It is suggested that, whereas glucagon, dibutyryl cyclic AMP and insulin modulate protein breakdown in these cells via changes in autophagocytosis, the stimulation by glucocorticoids is exerted independently, perhaps by stimulating the synthesis of membrane proteins essential to the autophagic process.

Frog glomerular vasotocin receptors resemble mammalian V1b receptors

1994 ◽  
Vol 267 (5) ◽  
pp. R1198-R1208 ◽  
Author(s):  
A. Ammar ◽  
R. M. Rajerison ◽  
S. Roseau ◽  
M. Bloch-Faure ◽  
D. Butlen
Keyword(s):  
Binding Sites ◽  
Inositol Phosphate ◽  
Rank Order ◽  
Enzyme Activation ◽  
Arginine Vasotocin ◽  
Pharmacological Properties ◽  
Nephron Segments ◽  
Inositol Phosphate Production ◽  
Vasopressin Receptors ◽  
Stimulation Of

Vasotocin receptors were investigated in glomeruli and nephron segments microdissected from collagenase-treated kidneys of Rana ridibunda, using [d(CH2)5Tyr(Me)2,Thr4,Orn8,125I-Tyr-NH2(9)]vasotocin (125I-OVTA) as a radioligand. Specific 125I-OVTA binding sites were found only in glomeruli and not in all tubule segments tested. Glomerular receptors exhibited the following stereospecificity for recognition of vasotocin analogues: Tyr-NH2(9)-LA-V1a > 125I-OVTA > arginine vasotocin (AVT) > or = [d(CH2)5Tyr-(Me)2]AVP > OVTA > or = [Phe2,Orn8]VT > oxytocin (OT) > or = [d(CH2)5-Sar7]AVP > desGly9[d(CH2)5Tyr(Et)2]VAVP > or = [d(CH2)5Tyr(Et)2]VAVP > AVP > [1-desamino-8-D-arginine]vasopressin (DDAVP) > [Thr4,Gly7]OT. In addition, vasotocin enhanced [3H]inositol phosphate production in sieved glomeruli labeled with myo-[3H]inositol; the rank order of structural vasotocin analogues for stimulation of phosphoinositidase C was [Phe2,Orn8]VT > AVT > OT > AVP > DDAVP, whereas [Thr4,Gly7]OT was almost inactive, and the rank order of antagonists for inhibition of hormone-induced enzyme activation was Tyr-NH2(9)-LA-V1a > [d(CH2)5Tyr(Me)2]AVP = OVTA > [d(CH2)5Sar7]AVP > [d(CH2)5Tyr(Et)2]VAVP > or = desGly9[d(CH2)5Tyr(Et)2]VAVP. Results indicate that the 125I-OVTA-labeled binding sites detected in frog glomeruli reveal the pharmacological properties of mammalian V1b-pituitary vasopressin receptors and might be physiological vasotocin receptors involved in phosphoinositidase C stimulation.

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