Decreased arachidonic acid liberation participates in the anti-aggregatory effect of the histamine H(1)-receptor antagonist Bromadryl.

The in vitro effect of the histamine H(1)-receptor antagonist Bromadryl on aggregation of human blood platelets was studied. Bromadryl inhibited stimulated platelet aggregation in a dose-dependent way. Depending on the aggregation stimulus used, its mean inhibitory concentrations were 16 micromol/litre (thrombin), 18 micro mol/litre (A23187), 92 micromol/litre (adrenaline) and 395 micromol/litre (adenosine diphosphate).

Inhibition of FMLP-stimulated neutrophil chemiluminescence by blood platelets increased in the presence of the serotonin-liberating drug chloroquine.

Introduction: Previously, we reported that human blood platelets significantly decreased the concentration of reactive oxygen species (chemiluminescence) produced by Ca(2+)-ionophore-stimulated neutrophils and that the reduction was partially mediated by serotonin liberated from platelets during their activation. The aim of the present study was to investigate whether platelet inhibition can occur independently of serotonin liberation and whether it can be pharmacologically enhanced.

Materials And Methods: Chemiluminescence was measured after stimulation of human neutrophils with N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) in the presence of luminophore luminol.

Effect of H1-antagonist Dithiaden on human PMN-leukocyte aggregation and chemiluminescence is stimulus-dependent.

Objective And Design: Contradictory data published on histamine-PMN leukocyte interactions stimulated us to study to the role of histamine and H1-antagonist Dithiaden in generation of reactive oxygen species (ROS) and aggregation of human neutrophils.

Methods And Materials: Whole blood or isolated PMN-leukocytes were exposed in a dose-dependent way to histamine or H1-antagonist Dithiaden and subsequently stimulated. Whole blood was stimulated with opsonised zymosan (OZ).

Antiplatelet activity of carvedilol in comparison to propranolol.

The non-selective vasodilating beta-blocker carvedilol was found to inhibit platelet aggregation as well as thromboxane B(2) formation more effectively than propranolol. The antiaggregatory activity of carvedilol decreased, depending on the stimulus used, in the following rank order of potency (in parentheses the respective mean inhibitory concentrations of carvedilol and propranolol are given in micromol/l): PMA (19 and 34) > thrombin (55 and 77) > Ca(2+)-ionophore A23187 (58 and 81) > epinephrine (86 and 118). However, aggregation of platelets activated with ADP was not affected by carvedilol in concentrations up to 100 micromol/l.

Human blood platelets, PMN leukocytes and their interactions in vitro. Responses to selective and non-selective stimuli.

Using simultaneous recording of aggregation and chemiluminescence, responses of human polymorphonuclear leukocytes, blood platelets and their mixture were investigated after stimulation by specific as well as non-specific stimuli for each cell. In our experimental settings, aggregation of platelets and PMN leukocytes was increased in the following order of stimuli: PMA View Article and Find Full Text PDF