Beta-adrenoceptor blocking drugs and calcium transport in isolated rat mast cells

The beta-adrenoceptor blocking (BAB) drugs exaprolol (EXA), metipranolol (MET) and propranolol (PRO) inhibited histamine liberation and degranulation from isolated rat mast cells stimulated with the calcium ionophore A23187. MET was the most and EXA the least active. Atenolol (ATE) had no effect. Inhibition by BAB drugs of secretion induced with A23187 was not accompanied by any change in 45Ca uptake. On the other hand, EXA, MET and PRO significantly decreased 45Ca uptake by mast cells stimulated with 48/80. The effect of BAB drugs on inhibition of A23187-induced secretion from isolated mast cells was dependent on the lipid solubility of the studied drugs.     

Membrane perturbing activity of beta-adrenoceptor blocking drugs in isolated rat mast cells

Beta-adrenoceptor blocking (BAB) drugs perturb the membranes of isolated rat mast cells. Membrane fluidisation was temperature dependent and was determined by the liposolubility of the BAB drugs. The secretory index, evaluated as the ratio between histamine liberation and degranulation, correlated with the membrane order parameter of the mast cell membranes. The rank order of potency for mast cell activation and membrane fluidisation was: exaprolol greater than propranolol greater than metipranolol greater than atenolol.     

Histidine transport by isolated rat peritoneal mast cells

Kinetic constants for the transport of [³H]histidine into isolated rat peritoneal mast cells were determined. The value of K_m for histidine transport was 44.0 μM; the value of V_max under the same conditions was 18.9 pinoles · min^? · (10⁶ cells)^?1. These parameters did not change in value after the addition of exogenous histamine. The uptake of histidine and its decarboxylation to histamine were relatively rapid processes compared to the transfer of the newly formed histamine into mast cell granules, so that nascent histaramine appeared transiently in the cytoplasm. Amino-acid competition experiments support the assignment of L system transport for the bulk of histidine uptake by mast cells. Metabolic inhibitors that deplete cellular ATP did not inhibit the uptake process.     

On the interaction of beta-adrenoceptor-blocking drugs with isolated mast cells

The interaction of beta-adrenoceptor blocking drugs (BAB drugs) with isolated mast cells resulted, according to the compound, in either a liberation of biogenic amines or an inhibition of stimulated amine release. The liberatory drugs exaprolol and K? 1124 decreased the level of cAMP, stimulated the activity of cyclic nucleotide-phosphodiesterase, decreased the incorporation of orthophosphate into membrane phospholipids and rapidly displaced calcium from binding sites in mast cells. The inhibitory drugs alprenolol, metipranolol, oxprenolol, practolol and propranolol, possessing lower liposolubility, produced opposite effects. Drugs from both groups displaced histamine from binding sites in isolated mast cell granules. The interaction of BAB drugs with mast cells is a result of non-specific rather than specific receptor interactions. Inhibitory drugs interfere with mast cells at membrane sites while liberatory drugs penetrate the membrane, thus acting both at the level of membrane and intracellularly.     

The effect of beta-adrenergic blocking drugs and inhibitors of phosphodiestease on histamine release from isolated mast cells.

Differences in the histamine liberation from isolated rat mast cells after beta-adrenergic blocking drugs were demonstrated. In equimolar concentrations histamine release was induced by K? 1124, K? 1500, K? 1560, K? 1561 and propranolol. Alprenolol, oxprenolol, propranolol, and trimepranol significantly decreased thehistamine release induced by compound 48-80. The release of granules from cells was inhibited quantitatively more than the release of histamine. This enabled us to surmise the selective effect of beta-adrenergic blocking drugs on cell membranes of mast cells. The possible mechanisms of release reaction are discussed.     

On the relationship between incorporation of 32P into phospholipids and binding of beta-adrenoceptor blocking drugs to isolated mast cells

The lipophilic beta-adrenoceptor blocking drugs exaprolol and propranolol significantly decreased the incorporation of 32P into phosphatidylethanolamine, phosphatidylcholine and phosphatidylinositol of isolated rat mast cells. In contrast, the hydrophilic drugs metipranolol, practolol and atenolol increased the incorporation of 32P into phosphatidylethanolamine, phosphatidylserine and phosphatidylinositol. The inhibition of 32P incorporation by lipophilic drugs correlated with the high binding of these drugs to mast cells.     

Evidence for intracellular histamine liberation in isolated rat mast cells

The beta-adrenoceptor blocking drug exaprolol liberated histamine from isolated rat mast cells in a dose- and time-dependent way. Histamine was liberated within seconds and was not followed by a parallel granule liberation. The inhibition of histamine liberation was induced with low temperature, low pH, high concentration of Ca2+, TTD, suramin and EDTA. Subcellular distribution of 3H-exaprolol demonstrated a quantitative relationship between histamine depletion against exaprolol uptake in isolated rat mast cell granules. A nonspecific mechanism of action in the effect of exaprolol on mast cells is discussed. It is proposed that the drug acts on mast cells due to the direct and indirect ion exchange mechanism resulted in disproportion between histamine and granule liberation.     

The effect of beta-adrenoceptor blocking drugs on histamine liberation, prostaglandin synthesis and phospholipid turnover in isolated mast cells stimulated with concanavalin A.

Exaprolol, metipranolol and propranolol decreased significantly histamine liberation, degranulation, 45Ca uptake and thromboxane B2 formation in isolated rat mast cells stimulated with concanavalin A and phosphatidylserine. Moreover, exaprolol and metipranolol decreased 32P incorporation into membrane phospholipids and metipranolol and propranolol reduced the liberation of arachidonic acid from membrane phospholipids of stimulated mast cells. Exaprolol significantly increased the arachidonic acid liberation from these cells. Possible mechanisms of interaction of beta-adrenoceptor blocking drugs with isolated mast cells are discussed.     

Effect of beta-adrenoceptor blocking drugs on 32P incorporation into and arachidonic acid liberation from phospholipids in stimulated rat mast cells

The lipophilic beta-adrenoceptor blocking (BAB) drugs metipranolol, propranolol and exaprolol significantly decreased 48/80- and A23187-induced 32P incorporation into rat mast cell phospholipids. Exaprolol was the most active, followed by propranolol and metipranolol. Atenolol and metipranolol significantly decreased the 48/80-stimulated, and metipranolol and exaprolol the A23187-stimulated 3H-arachidonic acid liberation from isolated mast cells.     

Immunological modulation of cholinergic histamine release in isolated rat mast cells

Isolated purified rat mast cells release histamine when exposed to acetylcholine according to different patterns of sensitivity. The degree of histamine release is correlated with the levels of reaginic antibodies presumably bound to the mast cell membrane. In fact, mast cells passively sensitized with mouse myeloma IgE against egg albumin or DNP2-lysine, react to acetylcholine with a release of histamine, which is proportional to the IgE concentration in the incubation medium. The histamine release induced by acetylcholine is due to the stimulation of a muscarinic receptor. Accordingly, acetylthiocholine is unable to evoke histamine release and preincubation of sensitized cells with atropine fully inhibits the cholinergic histamine release. The histamine release evoked by acetylcholine is potentiated by the exposure of sensitized cells to the specific antigen. The present results suggest that sensitization of mast cells is a crucial factor in modulating their sensitivity to acetylcholine.     

Dextran-induced release of serotonin from isolated rat peritoneal mast cells

Dextran (9 mg/ml incubate) was found to induce a serotonin (5-HT) release from isolated rat peritoneal mast cells of about 10% within an incubation period of 5 min. at 37 degrees. The extent of release was not increased by using higher concentrations of dextran or by increasing the incubation period from 5 to 20 min. The dextran-induced release of 5-HT was increased to 50-60% when the mast cells were preincubated with phosphatidylserine (PS) in doses of 2.6-4.3 microgram/ml incubate. Higher concentrations of PS alone induced a rapid 5-HT release of approximately 50-60%. The 5-HT release process studied was found to possess both similarities and dissimilarities with the previously described dextran-induced release process of histamine, also studied in isolated rat peritoneal mast cells. The results supported previous indirect evidence of a 5-HT release from mast cells in the early phase of the dextran-induced anaphylactoid reaction in the rat.     

Studies on histamine-retaining granules obtained from isolated rat mast cells.

Histamine-retaining granules were isolated from rat mast cells after sonication in either sucrose of Ficoll-Hypaque media. The preparations obtained were compared in regard to recovery and spontaneous loss of histamine. The effect of agents known to release histamine from intact rat mast cells (antigen, compound 48/80, decylamine, the ionophores A23187 and X537A as well as ATP) was studied on the granules. Antigen and compound 48/80 did not release histamine. Decylamine and X537A induced a pronounced release independent of the presence of divalent cations. ATP caused a small, but significant release, which showed an absolute requirement for magnesium. A23187 released histamine only in the presence of either calcium or magnesium, and this release was unaffected by certain agents known to inhibit histamine release from intact rat mast cells. The results seem to exclude the possibility that agents known to induce release of histamine from intact rat mast cells by a calcium-and energy-dependent process would exert this action through a direct effect on intracellularly localized granules.     

Quantitative correlation between histamine and 35S release from isolated rat mast cells due to the beta-adrenergic blocking drug K? 1124

An attempt was made to explain the mechanism of histamine release from isolated rat mast cells induced by the beta-adrenergic blocking drug K? 1124. This drug at the highest concentration used released 12 times more histamine than most other investigated beta-blockers. The release of histamine with K? 1124 was dose and temperature dependent. The maximal histamine release was at pH 8 and in the absence of calcium ions. Increased calcium concentration decreased histamine release significantly. The effect of K? 1124 on histamine release from mast cells was inhibited only by cocaine and 2,4-dinitrophenol; other metabolic inhibitors were ineffective. The histamine release due to K? 1124 was not followed by an equal release of 35S. Isoprenaline in equimolar concentration decreased histamine release induced by K? 1124 significantly. The release of 35S-labelled granules was decreased or blocked by isoprenaline.