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

Atenolol, exaprolol and mast cell membranes

Lipophilic exaprolol and hydrophilic atenolol differ in their interaction with mast cell membranes. Exaprolol, as compared with atenolol, significantly decreased 32P incorporation into, but increased arachidonic acid liberation from, membrane phospholipids. Moreover, exaprolol significantly decreased phosphate incorporation in compound 48/80 and ConA-PS treated cells and decreased thromboxane formation in stimulated cells. On the other hand, atenolol decreased significantly only arachidonate liberation from stimulated mast cells. These results corroborate to some extent the effect of exaprolol and atenolol on histamine liberation which correlates with their membrane perturbing properties.

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.

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.

Histamine liberation and membrane fluidisation of mast cells exposed to the beta-adrenoceptor blocking drug propranolol

Propranolol liberates histamine from isolated mast cells and decreases the uptake of extracellular histamine in a dose-dependent way. Histamine liberation due to propranolol is accompanied by calcium displacement from intracellular storage sites. The significant increase in membrane fluidity due to propranolol is temperature dependent. The perturbation of membranes is most probably the explanation of propranolol's interaction with isolated rat mast cells which results in altered histamine transportation.

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 Kö 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.

Presence of functionally active beta-adrenoceptors in rat mast cells. Correlation between (--)[3H]-dihydroalprenolol binding and inhibition of histamine release

The correlation between the binding of a beta-adrenoceptor antagonist, (--)[3H]-dihydroalprenolol (DHAP), and the adrenergic inhibition of histamine release by acetylcholine and by compound 48/80 was studied with isolated purified rat mast cells and in rat mast cell crude membrane fractions. Acetylcholine-evoked histamine release was inhibited by catecholamines, in the order isoprenaline greater than adrenaline greater than noradrenaline. Pretreatment of cells with (--)alprenolol antagonized the inhibitory effect of isoprenaline on acetylcholine-induced histamine release. 40/80-evoked histamine release was blocked by isoprenaline at significantly higher concentrations than those required to inhibit cholinergic histamine release. The inhibitory effect of isoprenaline was equally antagonized by preincubating mast cells with (--)alprenolol. Specific binding sites for DHAP have been demonstrated in rat mast cell membranes. The specific binding of DHAP was inhibited by adrenoceptor agonists and antagonists according to the stereospecificity of these compounds. A close correlation between the binding-inhibitory potency of various adrenergic compounds and the data obtained in the pharmacological experiments was found, thus indicating the presence of beta-adrenoceptors in rat 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.

On the mechanism by which theophylline inhibits histamine release from rat mast cells

Theophylline (2.5 mM) did not influence the spontaneous release of histamine but inhibited histamine release induced by antigen, compound 48/80 or phosphatidylserine. The effect on 48/80-induced histamine release could not be reversed by increasing extracellular Ca2+. Exogenous adenosine (10(-8) to 10(-4) M) did not influence spontaneous histamine release or 48/80-induced release but potentiated antigen-induced release. The adenosine potentiation was competitively inhibited by theophylline in concentrations (10(-5) to 10(-4) M) lower than those required to inhibit antigen-induced histamine release in the absence of adenosine. In order to see if endogenous adenosine levels are high enough to potentiate an anaphylactic histamine release in vivo, adenosine was determined in mast cell incubates and in plasma from 4 different strains of rat. The levels were 0.18 to 0.99 microM in plasma, which is sufficient to cause significant potentiation of histamine release, but only 3 x 10(-8) M in mast cell incubates. Theophylline (2.5 mM) increased cAMP levels about 100%, whereas adenosine (10(-5) M) had little effect on cAMP and cGMP levels. However, when incubated together, adenosine could inhibit the theophylline-induced increase in cAMP levels but not the inhibition of histamine release. It is concluded that the effect of low concentrations of theophylline could be due partly to antagonism of adenosine effects. In addition, in higher doses, theophylline appears to exert an inhibitory action that is unrelated to cyclic nucleotides, extracellular calcium and adenosine.

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

An attempt was made to explain the mechanism of histamine release from isolated rat mast cells induced by the beta-adrenergic blocking drug Kö 1124. This drug at the highest concentration used released 12 times more histamine than most other investigated beta-blockers. The release of histamine with Kö 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 Kö 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 Kö 1124 was not followed by an equal release of 35S. Isoprenaline in equimolar concentration decreased histamine release induced by Kö 1124 significantly. The release of 35S-labelled granules was decreased or blocked by isoprenaline.

What - if any - is the role of adrenergic mechanisms in histamine release from mast cells?

The effects of catecholamines on histamine release from rat peritoneal mast cells, was studied in an in vitro system. It was found that norepinephrine (10(-5)-101(-3) M) exerts a significant, dose related, repressive effect on compound 48/80-induced histamine release. This effect is greatly potentiated by beta-antagonists and is noticeable throughout the concentration range 10(-11)-10(-3) M norepinephrine. Phentolamine diminishes the repressive effect that norepinephrine shows at 10(-5) M. Norepinephrine (10(-5) M) totally inhibits the progressive histamine release induced by both compound 48/80 and strontium (10 muM) in non-Ca2+-depleted cells. The release that is dependent on extracellular calcium is inhibited by norepinephrine. The repressive effect of norepinephrine at 10(-3) is counteracted by 5.6 mM D-glucose, 2-deoxyglucose abolishes this effect. The repression of histamine release by 10(-5) M norepinephrine is not influenced by D-glucose. These results suggest that the effects on histamine release, observed within a low concentration range of norepinephrine (less than 10(-3) M), may be due to alpha-adrenoreceptor mechanisms and an interference in transmembrane calcium transport. Our data further suggest that norepinephrine at 10(-3) M may inhibit oxidative phosphorylation. Isoproterenol and epinephrine (10(-9)-10(-5) M) show little effect on 48/80-induced histamine release in a normal medium. However, when calcium is excluded from the medium, histamine release is potentiated. These results seem to indicate that isoproterenol and epinephrine act by displacing intracellular calcium, making it available for the exocytosis process.

The release of serotonin from rat duodenal enterochromaffin cells by adrenoceptor agonists studied in vitro

The serotonin (5-HT) content of enterochromaffin cells (EC) was studied by a cytofluorimetric method in biopsies from rat duodenal mucosa after in vitro incubation with different adrenoceptor agonists and antagonists and acetylcholine (ACh). Noradrenaline (NA), Adrenaline (A) and Isoprenaline (IP) caused a decrease of 5-HT in EC down to 40--60% and for NA and A this effect was concentration-dependent. The effect was antagonized by d,1-propranolol but not by d-propranolol, metoprolol, phentolamine or phenoxybenzamine indicating that the 5-HT release from EC is probably mediated via a true beta-adrenoceptor mechanism possibly of the beta2 type. ACh also decreased the 5-HT content of EC but was much less potent than the adrenergic substances. Dopamine (DA) had no effect.