scholarly journals Inositol trisphosphates in carbachol-stimulated rat parotid glands

1984 ◽  
Vol 223 (1) ◽  
pp. 237-243 ◽  
Author(s):  
R F Irvine ◽  
A J Letcher ◽  
D J Lander ◽  
C P Downes
Keyword(s):  
Parotid Gland ◽  
Inositol Trisphosphate ◽  
Erythrocyte Membranes ◽  
Parotid Glands ◽  
Phosphatidylinositol Bisphosphate ◽  
Rat Parotid Gland ◽  
Periodate Treatment ◽  
Human Erythrocyte Membranes ◽  
Rat Parotid ◽  
Stimulation Of

Carbachol stimulation of rat parotid gland fragments prelabelled with myo-[3H]-inositol results in a large accumulation after 15 min of [3H]inositol trisphosphate. Only some of this is the D-1,4,5 isomer which would be expected to be derived from the known phosphatidylinositol bisphosphate. The predominant inositol trisphosphate is not susceptible to hydrolysis by human erythrocyte membranes. It yields altritol after periodate treatment followed by reduction and dephosphorylation, and, from partial dephosphorylation experiments, does not have a phosphate in the 2 position; the most likely structure of this inositol trisphosphate is therefore (D/L)-myo-inositol 1,3,4-trisphosphate. The possible origin and significance of this compound are discussed.

scholarly journals Inositol 1,3,4,5-tetrakisphosphate and not phosphatidylinositol 3,4-bisphosphate is the probable precursor of inositol 1,3,4-trisphosphate in agonist-stimulated parotid gland

1986 ◽  
Vol 238 (2) ◽  
pp. 501-506 ◽  
Author(s):  
C P Downes ◽  
P T Hawkins ◽  
R F Irvine
Keyword(s):  
Parotid Gland ◽  
Prolonged Exposure ◽  
Inositol Trisphosphate ◽  
Erythrocyte Membranes ◽  
Head Group ◽  
Inositol Polyphosphate ◽  
Parotid Glands ◽  
Phosphatidylinositol Bisphosphate ◽  
Inositol Tetrakisphosphate ◽  
Rat Parotid

When [3H]inositol-prelabelled rat parotid-gland slices were stimulated with carbachol, noradrenaline or Substance P, the major inositol trisphosphate produced with prolonged exposure to agonists was, in each case, inositol 1,3,4-trisphosphate. Much lower amounts of radioactivity were present in the inositol 1,4,5-trisphosphate fraction separated by anion-exchange h.p.l.c. Analysis of the inositol trisphosphate head group of phosphatidylinositol bisphosphate in [32P]Pi-labelled parotid glands showed the presence of phosphatidylinositol 4,5-bisphosphate, but no detectable phosphatidylinositol 3,4-bisphosphate. Carbachol-stimulated [3H]inositol-labelled parotid glands contained an inositol polyphosphate with the chromatographic properties and electrophoretic mobility of an inositol tetrakisphosphate, the probable structure of which was determined to be inositol 1,3,4,5-tetrakisphosphate. Since an enzyme in erythrocyte membranes is capable of degrading this tetrakisphosphate to inositol 1,3,4-trisphosphate, it is suggested to be the precursor of inositol 1,3,4-trisphosphate in parotid glands.

scholarly journals The relationship of calcium to receptor-controlled stimulation of phosphatidylinositol turnover. Effects of acetylcholine, adrenaline, calcium ions, cinchocaine and a bivalent cation ionophore on rat parotid-gland fragments

1975 ◽  
Vol 148 (3) ◽  
pp. 479-485 ◽  
Author(s):  
L M Jones ◽  
R H Michell
Keyword(s):  
Parotid Gland ◽  
De Novo ◽  
Head Group ◽  
Ionophore A23187 ◽  
Bivalent Cation ◽  
Phosphatidylinositol Turnover ◽  
Rat Parotid Gland ◽  
Muscarinic Cholinergic ◽  
Rat Parotid ◽  
Stimulation Of

The possibility that Ca2+ ions are involved in the control of the increased phosphatidylinositol turnover which is provoked by alpha-adrenergic or muscarinic cholinergic stimulation of rat parotid-gland fragments has been investigated. Both types of stimulation provoked phosphatidylinositol breakdown, which was detected either chemically or radiochemically, and provoked a compensatory synthesis of the lipid, detected as an increased rate of incorporation of 32Pi into phosphatidylinositol. Acetylcholine had little effect on the incorporation of labelled glycerol, whereas adrenaline stimulated it significantly, but to a much lower extent than 32P incorporation: this suggests that the response to acetylcholine was entirely accounted for by renewal of the phosphorylinositol head-group of the lipid, but that some synthesis de novo was involved in the response to adrenaline. The responses to both types of stimulation, whether measured as phosphatidylinositol breakdown or as phosphatidylinositol labelling, occurred equally well in incubation media containing 2.5 mm-Ca2+ or 0.2 mm-EGTA [ethanedioxybis(ethylamine)-tetra-acetic acid]. Incubation with a bivalent cation ionophore (A23187) led to a small and more variable increase in phosphatidylinositol labelling with 32Pi, which occurred whether or not Ca2+ was available in the extracellular medium: this was not accompanied by significant phosphatidylinositol breakdown. Cinchocaine, a local anaesthetic, produced parallel increases in the incorporation of Pi and glycerol into phosphatidylinositol. This is compatible with its known ability to inhibit phosphatidate phosphohydrolase (EC 3.1.3.4) and increase phosphatidylinositol synthesis de novo in other cells. These results indicate that the phosphatidylinositol turnover evoked by alpha-adrenergic or muscarinic cholinergic stimuli in rat parotid gland probably does not depend on an influx of Ca2+ into the cells in response to stimulation. This is in marked contrast with the K+ efflux from this tissue, which is controlled by the same receptors, but is strictly dependent on the presence of extracellular Ca2+. The Ca2+-independence of stimulated phosphatidylinositol metabolism may mean that it is controlled through a mode of receptor function different from that which controls other cell responses. Alternatively, it can be interpreted as indicating that stimulated phosphatidylinositol breakdown is intimately involved in the mechanisms of action of alpha-adrenergic and muscarinic cholinergic receptor systems.

scholarly journals Metabolism of inositol 1,4,5-trisphosphate and inositol 1,3,4-trisphosphate in rat parotid glands

1985 ◽  
Vol 229 (2) ◽  
pp. 505-511 ◽  
Author(s):  
R F Irvine ◽  
E E Anggård ◽  
A J Letcher ◽  
C P Downes
Keyword(s):  
High Performance ◽  
Inositol Trisphosphate ◽  
Significant Proportion ◽  
Complete Separation ◽  
Parotid Glands ◽  
Phosphatidylinositol Bisphosphate ◽  
Metabolic Characteristics ◽  
Inositol 1,4,5 Trisphosphate ◽  
Rat Parotid ◽  
And Control

A complete separation of myo-inositol 1,4,5-[4,5-(32)P]trisphosphate prepared from human erythrocytes, and myo-[2-3H]inositol 1,3,4-trisphosphate prepared from carbachol-stimulated rat parotid glands [Irvine, Letcher, Lander & Downes (1984) Biochem. J. 223, 237-243], was achieved by anion-exchange high-performance liquid chromatography. This separation technique was then used to study the metabolism of these two isomers of inositol trisphosphate in carbachol-stimulated rat parotid glands. Fragments of glands were pre-labelled with myo-[2-3H]inositol, washed, and then stimulated with carbachol. At 5s after stimulation a clear increase in inositol 1,4,5-trisphosphate was detected, with no significant increase in inositol 1,3,4-trisphosphate. After this initial lag however, inositol 1,3,4-phosphate rose rapidly; by 15s it predominated over inositol 1,4,5-trisphosphate, and continued to rise so that after 15 min it was at 10-20 times the radiolabelling level of the 1,4,5-isomer. In contrast, after the initial rapid rise (maximal within 15s), inositol 1,4,5-trisphosphate levels declined to near control levels after 1 min and then rose again very gradually over the next 15 min. When a muscarinic blocker (atropine) was added after 15 min of carbachol stimulation, inositol 1,4,5-trisphosphate levels dropped to control levels within 2-3 min, whereas inositol 1,3,4-trisphosphate levels took at least 15 min to fall, consistent with the kinetics observed earlier for total parotid inositol trisphosphates [Downes & Wusteman (1983) Biochem. J. 216, 633-640]. Phosphatidylinositol bisphosphate (PtdInsP2) from stimulated and control cells were degraded chemically to inositol trisphosphate to seek evidence for 3H-labelled PtdIns(3,4)P2. No evidence could be obtained that a significant proportion of PtdInsP2 was this isomer; in control tissues it must be less than 5% of the total PtdInsP2 radiolabelled by myo-[2-3H]inositol. These data indicate that, provided that inositol 1,4,5-trisphosphate is studied independently of inositol 1,3,4-trisphosphate, the former shows metabolic characteristics consistent with its proposed role as a second messenger for calcium mobilization. The metabolic profile of inositol 1,3,4-trisphosphate is entirely different, and its function and source remain unclear.

scholarly journals Sympathetic denervation impairs agonist-stimulated phosphatidylinositol metabolism in rat parotid glands

1983 ◽  
Vol 214 (3) ◽  
pp. 865-870 ◽  
Author(s):  
C P Downes ◽  
M D Dibner ◽  
M R Hanley
Keyword(s):  
Substance P ◽  
Parotid Gland ◽  
Membrane Lipid ◽  
Sympathetic Denervation ◽  
Parotid Glands ◽  
Surface Receptors ◽  
Alpha Adrenoceptor ◽  
Inositol Phospholipids ◽  
Rat Parotid Gland ◽  
Rat Parotid

Substance P, muscarinic and alpha-adrenoceptor agonists stimulated the incorporation of [3H]inositol into phosphatidylinositol in rat parotid gland slices. Surgical denervation of the sympathetic input to the rat parotid gland by superior cervical ganglionectomy produced marked reductions in these responses. The stimulated incorporation of radiolabelled precursors into phosphatidylinositol is a measure of its resynthesis after receptor-mediated breakdown of inositol phospholipids. We therefore examined the enzymic site of the lesion induced by sympathetic denervation using parotid gland slices labelled with either [3H]inositol or [32P]phosphate and stimulated with substance P. Receptor-activated phospholipase C attack upon [3H]inositol phospholipids was assayed by measuring the formation of [3H]inositol 1-phosphate in the presence of 10 mM-Li+ to inhibit further breakdown. It was not affected by denervation. Substance P elicited a rapid breakdown of phosphatidylinositol 4,5-bisphosphate and this response was reduced in the denervated gland. The second step in stimulated phosphatidylinositol turnover, phosphorylation of diacylglycerol to phosphatidate was not affected by denervation. Sympathetic denervation appears to induce a specific enzymic lesion in the parotid gland that impairs receptor-stimulated resynthesis of phosphatidylinositol from phosphatidate. This change in membrane lipid metabolism may be related to a number of the effects of sympathetic denervation, such as agonist supersensitivity, reduced gland cell proliferation and induction of new surface receptors.

scholarly journals Ryanodine and inositol trisphosphate receptors are differentially distributed and expressed in rat parotid gland

1999 ◽  
Vol 340 (2) ◽  
pp. 519 ◽  
Author(s):  
Xuejun ZHANG ◽  
Jiayu WEN ◽  
Keshore R. BIDASEE ◽  
Henry R. BESCH, JR ◽  
Richard J.H. WOJCIKIEWICZ ◽  
...  
Keyword(s):  
Parotid Gland ◽  
Inositol Trisphosphate ◽  
Inositol Trisphosphate Receptors ◽  
Rat Parotid Gland ◽  
Rat Parotid
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