scholarly journals Properties of receptor-controlled inositol trisphosphate formation in parotid acinar cells

1985 ◽  
Vol 225 (1) ◽  
pp. 263-266 ◽  
Author(s):  
D L Aub ◽  
J W Putney
Keyword(s):  
Inositol Phosphates ◽  
Inositol Trisphosphate ◽  
Calcium Ionophore ◽  
Acinar Cells ◽  
Receptor Occupancy ◽  
Parotid Acinar Cells ◽  
Parotid Cells ◽  
Rat Parotid ◽  
K Release ◽  
Substance P Receptors

Activation of muscarinic receptors in rat parotid cells results in breakdown of polyphosphoinositides liberating inositol phosphates, including inositol trisphosphate. Formation of inositol trisphosphate appears independent of agonist-induced Ca2+ mobilization, since neither formation nor degradation of inositol trisphosphate are appreciably altered in low-calcium media, and elevation of cytosolic Ca2+ with a calcium ionophore does not cause an increase in cellular inositol trisphosphate. Further, activation of substance P receptors and alpha 1-adrenoreceptors, but not beta-adrenoreceptors, increases inositol trisphosphate formation. The dose-response curve for methacholine activation of inositol trisphosphate formation more closely approximates the curve for receptor occupancy than for Ca2+-activated K+ release. These results are all consistent with the suggestion that inositol trisphosphate could function as a second messenger linking receptor occupation to cellular Ca2+ mobilization.

scholarly journals Capacitative calcium entry in parotid acinar cells

1989 ◽  
Vol 258 (2) ◽  
pp. 409-412 ◽  
Author(s):  
H Takemura ◽  
J W Putney
Keyword(s):  
Plasma Membrane ◽  
Inositol Phosphates ◽  
Second Messengers ◽  
Acinar Cells ◽  
Receptor Activation ◽  
Initial Increase ◽  
Muscarinic Agonist ◽  
Plasma Membrane Permeability ◽  
Parotid Acinar Cells ◽  
Parotid Cells

The intracellular Ca2+ indicator, fura-2, was used to monitor changes in cytosolic [Ca2+] in parotid acinar cells. When parotid cells were incubated in a medium containing low [Ca2+], and [Ca2+] was restored to the physiological range, there was a small increase in cytosolic [Ca2+]. If, however, the cells were first activated by a muscarinic agonist, and receptor activation was terminated before the addition of Ca2+ by the addition of a pharmacological excess of the muscarinic-receptor antagonist atropine, the initial increase in cytosolic [Ca2+] was faster and transiently larger than in the control cells which had not been previously stimulated. This suggested that a stimulation of Ca2+ entry occurred owing to the prior emptying of the agonist-regulated intracellular Ca2+ pool. This extra Ca2+ influx seen in pool-depleted cells persisted even when the interval between the addition of atropine and Ca2+ was increased from 1 to 20 min. Also, when the pool was allowed to refill by adding atropine in the presence of extracellular Ca2+, and Ca2+ was then sequentially removed and restored, the rise in cytosolic [Ca2+] after the addition of extracellular Ca2+ was not rapid, and resembled the increase seen in unstimulated cells. These results indicate that, when the agonist-sensitive Ca2+ pool is emptied by an agonist, Ca2+ influx across the plasma membrane is increased. This influx of Ca2+ occurs independently of the concentrations of inositol phosphates and probably of any second messengers linked directly to receptor activation. It appears rather to be a consequence of the empty state of the Ca2+ pool. Further, we suggest that, whenever the agonist-sensitive Ca2+ pool is emptied by agonist activation, the plasma-membrane permeability to Ca2+ will be increased, and this may account, at least in part, for the phenomenon of receptor-activated Ca2+ entry.

scholarly journals Ryanodine receptor expression is associated with intracellular Ca2+ release in rat parotid acinar cells

1997 ◽  
Vol 273 (4) ◽  
pp. C1306-C1314 ◽  
Author(s):  
Xuejun Zhang ◽  
Jiayu Wen ◽  
Keshore R. Bidasee ◽  
Henry R. Besch ◽  
Ronald P. Rubin
Keyword(s):  
Ryanodine Receptor ◽  
Acinar Cells ◽  
Receptor Expression ◽  
Intact Cells ◽  
Parotid Acinar Cells ◽  
Cyclic Adp Ribose ◽  
Parotid Cells ◽  
Intracellular Ca ◽  
Rat Parotid

The ryanodine receptor mediates intracellular Ca2+ mobilization in muscle and nerve, but its physiological role in nonexcitable cells is less well defined. Like adenosine 3′,5′-cyclic monophosphate and inositol 1,4,5-trisphosphate, cyclic ADP-ribose (0.3–5 μM) and ADP (1–25 μM) produced a concentration-dependent rise in cytosolic Ca2+ in permeabilized rat parotid acinar cells. Adenosine and AMP were less effective. Ryanodine markedly depressed the Ca2+-mobilizing action of the adenine nucleotides and forskolin in permeabilized cells and was likewise effective in depressing the action of forskolin in intact cells. Cyclic ADP-ribose-evoked Ca2+ release was enhanced by calmodulin and depressed by W-7, a calmodulin inhibitor. A fluorescently labeled ligand, 4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3,4-diaza-s-indacene-3-propionic acid-glycyl ryanodine, was synthesized to detect the expression and distribution of ryanodine receptors. In addition, ryanodine receptor expression was detected in rat parotid cells with a sequence highly homologous to a rat skeletal muscle type 1 and a novel brain type 1 ryanodine receptor. These findings demonstrate the presence of a ryanodine-sensitive intracellular Ca2+ store in rat parotid cells that shares many of the characteristics of stores in muscle and nerve and may mediate Ca2+-induced Ca2+ release or a modified form of this process.

scholarly journals β-Adrenergic stimulation alters oligosaccharide pyrophosphoryl dolichol metabolism in rat parotid acinar cells

1985 ◽  
Vol 231 (2) ◽  
pp. 431-438 ◽  
Author(s):  
S R Grant ◽  
E E Kousvelari ◽  
D K Banerjee ◽  
B J Baum
Keyword(s):  
Half Life ◽  
Specific Radioactivity ◽  
Acinar Cells ◽  
Protein Glycosylation ◽  
Significant Enhancement ◽  
Adrenergic Stimulation ◽  
Parotid Acinar Cells ◽  
Secretory Glycoproteins ◽  
Rat Parotid ◽  
Stimulation Of

beta-Adrenergic stimulation of rat parotid acinar cells markedly increases [3H]mannose incorporation into N-linked glycoproteins [Kousvelari, Grant, Banerjee, Newby & Baum (1984) Biochem. J. 222, 17-24]. More than 90% of this protein-bound [3H]mannose was preferentially incorporated into four secretory glycoproteins. The ratio of [3H]mannose/[14C]leucine present in these individual proteins was 1.7-4-fold greater with isoproterenol-treated cells than with untreated controls. In isoproterenol-stimulated cells, [3H]mannose incorporation into mannosylphosphoryl dolichol and oligosaccharide-PP-dolichol was increased 2-3-fold over that observed in unstimulated cells. Similarly, formation of mannosylated oligosaccharide-PP-dolichol was increased approx. 4-fold in microsomes prepared from isoproterenol-treated cells. Also, turnover of oligosaccharide-PP-dolichol was significantly increased (5-fold) by β-adrenergic stimulation; the half-life for oligosaccharide-PP-dolichol decreased from 6 min in control cells to 1.2 min in isoproterenol-stimulated cells. By 15 min after isoproterenol addition to acinar cells, the specific radioactivity of parotid oligosaccharide moieties increased about 3-fold over the value observed in the absence of the agonist. Taken together, these results strongly suggest that elevation of N-linked protein glycosylation in rat parotid acinar cells after β-adrenoreceptor stimulation resulted from significant enhancement in the synthesis of mannosylphosphoryl dolichol and oligosaccharide-PP-dolichol and the turnover of oligosaccharide-PP-dolichol.

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