ABSTRACT
The effect of thrombin, an agonist of proteinase-activated receptor (PAR) family, was studied on cultured rat hippocampal neurons. Thrombin in a concentration range of 1 pM - 10 nM induced a transitory dose-dependent increase in intracellular free calcium concentration. Involvement of PAR1 in neural response to thrombin was corroborated in experiments with TFLLRN, a selective synthetic peptide agonist of these receptors. In a calcium-free medium and after treatment with cyclopiazonic acid (inhibitor of Ca(2+)-ATPase in the endoplasmic reticulum) activation of PAR not only mobilized Ca(2+) from intracellular stores, but also induced Ca(2+) entry into the cells. Thrombin decreased Ca(2+) signal triggered by activation of NMDA-subtype glutamate receptors.
Subject(s)
Calcium/metabolism , Hippocampus/metabolism , Neurons/metabolism , Thrombin/physiology , Animals , Calcium/analysis , Cells, Cultured , Hippocampus/cytology , Indoles/pharmacology , Neurons/chemistry , Neurons/drug effects , Rats , Rats, Wistar , Thrombin/pharmacologyABSTRACT
Dose-dependent release of beta-hexoaminidase induced with thrombin was shown to be mediated by the PAR-1. This was further confirmed by means of agonist, antagonist and PAR desensitization. Acceleration of the mast cell mediator secretion by the Xa factor and PAR-2 agonist, was revealed. An increase in the mast cell release induced by thrombin and TRAP-6 was shown in the acute peritonitis model.
Subject(s)
Mast Cells/metabolism , Peritonitis/metabolism , Receptors, Thrombin/metabolism , Acute Disease , Animals , Cathepsin G , Cathepsins/pharmacology , Histamine Release , In Vitro Techniques , Mast Cells/enzymology , Peptide Fragments/pharmacology , Rats , Receptor, PAR-1 , Receptor, PAR-2 , Receptors, Thrombin/agonists , Receptors, Thrombin/antagonists & inhibitors , Serine Endopeptidases , Thrombin/pharmacology , Thrombin/physiology , beta-N-Acetylhexosaminidases/metabolismABSTRACT
In vivo experiments on the model of wound healing showed that thrombin and thrombin receptor agonist TRAP-6 stimulated heparin secretion by mast cells in rat subcutaneous fat: the saturation of mast cells with heparin decreased, while degranulation and granulolysis increased. In vitro studies showed that TRAP-6 caused a dose-dependent release of beta-hexosaminidase from peritoneal mast cells. TRAP-6 also induced heparin release from these cells and inhibition of amidase activity of thrombin. Heparin released from mast cells had low anticoagulant activity. These data suggest that activation of mast cells with thrombin is mediated by PAR-1.
Subject(s)
Mast Cells/physiology , Receptors, Thrombin/physiology , Animals , Cell Degranulation , Female , Male , Rats , Receptor, PAR-1 , Signal Transduction , Thrombin/physiology , Wound HealingABSTRACT
Thrombin, binding to receptors of the protease activated receptor (PAR) family, is involved in wound healing by inducing the reparation processes and regulating the activity of mast cells, which secrete mediators of inflammation. Using thrombin receptor agonist peptide (TRAP-6) for the activation of rat mast cells, effect of several receptors, including PAR-1, on mast cells was demonstrated. It was shown that TRAP increases the concentration of Ca2+ in the cytoplasm of mast cells and regulates cell degranulation, while releasing nitrogen oxide. Thrombin encapsulated in poly(N-vinyl caprolactam)-calcium alginate (PVCL-Ca-Alg) hydrogel films promotes wound healing in rats as demonstrated by the acceleration of fibroblast proliferation and neovascularization.
Subject(s)
Peptide Fragments/pharmacology , Receptors, Thrombin/agonists , Thrombin/physiology , Wound Healing/physiology , Animals , Calcium/metabolism , Caprolactam/analogs & derivatives , Caprolactam/chemistry , Cell Degranulation/drug effects , Cytoplasm/drug effects , Cytoplasm/metabolism , Drug Compounding , Mast Cells/drug effects , Mast Cells/metabolism , Neovascularization, Physiologic/drug effects , Nitric Oxide/metabolism , Polymers/chemistry , Rats , Wound Healing/drug effectsABSTRACT
With a view of decoding the mechanisms of their action the effect of papaverine, chlorpromazine and imipramine produced on a number of blood platelets hemostatic functions was studied. All the three drugs suppress in a characteristic fashion the aggregation on blood platelets caused by thrombin in the Tyrode solution and in a plasma defibrilated by heating, as well as by collogen and ADP in the citrated plasma. Unlike chlorpromazine and imipramine papaverine exerts a strong inhibiting action on the phosphodiesterase activity. Chlorpromazine and imipramine suppress the absorption of serotonin and retraction more intensively than this is done by papaverine and call forth morphological changes in the blood platelets that proceed parallel with changes in the intensity of the photodiffusion and liberation of endogenous serotonin. It is postulated that chlorpromazine and imipramine manifest their inhibitory effect through nonspecific damage of the blood platelets membranes, whereas papaverine does this through exchange of adenine-nucleotides and, especially, of 3',5'-AMP.
