by N Negrev

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In our previous studies we established that in normal conditions rat thrombo-cytopoiesis and plasma thrombocytopoietin activity depended directly on the functional state of beta-adrenergic receptors (7, 8). The aim of the present work is to determine the extent to which non-selective beta-adrenergic actions influence thrombocyte and megakaryocyte number in thromboplastin induced acute thrombocytopenia. It will permit us to establish the role of beta-adrenergic receptors in thrombocytopoiesis regulation in extreme conditions. Material and methods The study covered 53 white male rats of Wistar breed with 180-200 g body weight divided into three groups. I s t-injected with Isoprenaline (IP) hydro-chloride (a non-selective beta-adrenostimulator) at dosis 2x3 mg/kg b. \v.; II n d-with Propranolol (PR) hydrochloride (a non-selective beta-adreno-blocker) at dosis 2x5 mg/kg b. w., and III rd-with saline (PS) in the same amount (controls). The experiment duration was 24 h and the injections with adrenergic agents and PS twice every 12 h intraperitoneally. 3 h after first injection thromboplastin (TP) was injected after the scheme of Kelemen et al. (1963) in our modification. TP produced by the Research Institute of Hematology and Transfusion-Sofia was used in our study. The first injection was done i.v. in the tail vein in vol. 0,5.10-6 m 3 but the second one after 40 min intraperitoneally in vol. 1.10-6 m 3 .Thrombocyte count was determined after the method of Feissly-Liidin (cited after 9) at the beginning and the end of the assay as well as megakaryocyte line cells of 33 animals only by using bone-marrow smears prepared after the routine method (9). Megakaryo-cyte classification was done after Levine et al. (1982). The data were processed by the methods of variation statistics. Results and discussion The comparison of the changes of thrombocyte count shows that it increases insignificantly (0,75 per cent) in IP+TR treated animals, it decreases with 51,97 per cent (p <0,001) in PR+TR treated ones but with 30,96 per cent (p <0,002) in PS+TR treated ones (see fig. 1). The changes of bone-marrow megakaryocytes (see table 1). show that IP-fTR treatment causes a total megakaryocyte increase with 50 per cent (p<0,001). I s t and II n d stage megakaryocytes decreased with 49 per cent (p<0,001) and 3,20 per cent, respectively, but III rd and IV th stage ones increased with 161 per cent (p<0,001) and 263 per cent (p<0,001), respectively. In PR-f
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