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Balija M.,Croatian Institute of Transfusion Medicine | Bordukalo-Niksic T.,Ruder Boskovic Institute | Mokrovic G.,Ruder Boskovic Institute | Banovic M.,University of Zagreb | And 2 more authors.
Clinica Chimica Acta | Year: 2011

Background: Although it is known that platelet serotonin level (PSL) depends directly on platelet serotonin uptake (PSU) through the plasma membrane, reports on their interrelation are inconsistent. The aim of this study was to systematically explore the relationship between these two platelet serotonin parameters in large human population. Methods: PSL and full-kinetics of PSU were determined on 318 blood donors (276 males, 42 females; 20-67. years). Results: The overall correlation coefficient between PSL and maximal velocity of PSU was highly significant but unexpectedly low (r=0.269). Further analyses revealed lack of correlation among females, and variable association among males, depending on the subject age and season of measurements. Highly significant correlations were observed in spring-winter, while association was absent during summer-autumn. Lowering of PSL-PSU correlation with increased age was also demonstrated, showing modest interrelation among younger men and no interrelation in older population. By multiple regression analyses season was identified as the only independent predictor of PSL-PSU relationship. Conclusions: The results show prominent influence of biological (sex, age) and, especially, environmental (seasons) physiology on the intraindividual relationship between PSL and PSU. Although serotonin transporter activity plays an important role in determining PSL, the observed correlations indicate that other factors may predominate. © 2010 Elsevier B.V. Source


Bojic M.,University of Zagreb | Debeljak Z.,University of Zagreb | Debeljak Z.,Laboratory Diagnostics | Tomciic M.,Croatian Institute of Transfusion Medicine | And 2 more authors.
Nutrition Journal | Year: 2011

Background: Among natural compounds, present in every day diet, flavonoids have shown beneficial effect in prevention of cardiovascular diseases that can be attributed, at least partially to the described antiaggregatory activity i.e. antiplatelet effects of flavonoids. Due to the ever increasing pharmacological interest in antiplatelet agents a systematic experimental evaluation of large flavonoid series is needed. Methods. A set of thirty flavonoid aglycones has been selected for the evaluation. All measurements of aggregation were done under standardized and firmly controlled in vitro conditions. The whole blood samples, multiple platelet functional analyzer and adenosine diphosphate (ADP) as a weak agonist of aggregation were selected for this purpose. Results: The results were expressed as minimal concentration of flavonoid that can significantly lower the platelet aggregation compared to the corresponding untreated sample (minimal antiaggregatory concentration - MINaAC). All analyzed flavonoids exhibited antiaggregatory activity MINaAC ranging from 0.119 M to 122 M, while the most potent representatives were 3,6-dihydroxyflavone (0.119 M) and syringetin (0.119 M). Conclusions: Measurable antiplatelet activity established at submicromolar flavonoid concentrations suggests that even a dietary consumption of some flavonoids can make an impact on in vivo aggregation of platelets. These findings also point out a therapeutical potential of some flavonoids. © 2011 Boji et al; licensee BioMed Central Ltd. Source


Banovic M.,University of Zagreb | Bordukalo-Niksic T.,Ruder Boskovic Institute | Balija M.,Croatian Institute of Transfusion Medicine | Cicin-Sain L.,Ruder Boskovic Institute | Jernej B.,Ruder Boskovic Institute
Platelets | Year: 2010

The present study had two goals: first, to give a detailed description of a reliable method for full kinetic analysis of serotonin transporter (5HTt) on the membrane of human platelets, and second, as a main issue, to report on physiological influences on kinetic characteristics of this transmembrane transport on a large population of healthy individuals. Full kinetic analyses of platelet serotonin uptake were performed on 334 blood donors of both sexes by the use of 14C-radioisotopic method, which was first optimized according to assumptions of enzyme kinetic analyses, with regard to platelet concentration, duration of uptake, concentration of substrate as well as important technical parameters (underpressure of filtration, blanks, incubating temperature, etc). Kinetic parameters of platelet serotonin uptake in the whole population were for Vmax: 142 ± 25.3 pmol 5HT/108 platelets/minute and for Km: 0.404 ± 0.089 M 5HT. Besides the report on kinetic values of 5HT transporter protein, we have also described major physiological influences on the mentioned parameters, Vmax, Km and their derivative, Vmax/Km (transporter efficiency): range and frequency distribution of normal values, intraindividual stability over time, lack of age influence, gender dependence and seasonal variations. The report on kinetic values and main physiological influences on platelet serotonin transport kinetics, obtained by the use of thoroughly reassessed methodology, and on by far the largest human population studied until now, offers a reliable frame of reference for pathophysiological studies of this parameter in various clinical fields. © 2010 Informa UK Ltd. Source


Bojic M.,University of Zagreb | Debeljak Z.,University of Zagreb | Debeljak Z.,Clinical Hospital Center Osijek | Marica-Medic-Saric,University of Zagreb | Tomicic M.,Croatian Institute of Transfusion Medicine
Clinical Chemistry and Laboratory Medicine | Year: 2012

Background: Flavonoids are widely distributed across the plant kingdom and are therefore common ingredients in an everyday diet. Some flavonoids have a potential to affect platelet aggregation; most often antiaggregatory effects of flavonoids are observed. The objective of this research was to evaluate the in vitro effect of a selected set of flavonoids on platelet aggregation in whole blood. Methods: The effect of five selected flavonoids (pinocembrin-7- methylether, epicatechin, hesperetin, 6-hydroxyflavone and 3,6-dihydroxyflavone) on platelet aggregation was studied in the citrated whole blood samples collected from 75 healthy volunteers. A Multiplate® impedance analyzer and five different aggregation inducers (ADP, arachidonic acid, collagen, ristocetin and TRAP-6) were utilized for the analysis of samples. Results: Minimal antiaggregatory concentrations (MINaAC) of flavonoids in individual tests were reported in the following ranges: 0.12-1.91 μM; 15.26-244.14 μM; 15.26-122.07 μM; and 0.06-15.26 μM for ADP, collagen, TRAP-6 and ristocetin aggregation-inducers, respectively. When arachidonic acid was used for induction of platelet aggregation, a proaggregatory effect was observed for pinocembrin-7-methylether, epicatechin, hesperetin and 3,6-dihydroxyflavone, while the expected antiaggregatory effect was observed only for 6-hydroxyflavone (MINaAC=7.63 μM). Conclusions: Flavonoids interfere with in vitro platelet aggregation assays exhibiting either anti- or proaggregatory effects in concentration ranges that can be achieved in circulation by dietary intake. Thus, dietary intake of flavonoids should be taken into account when interpreting the results of whole blood platelet aggregation. © 2012 by Walter de Gruyter • Berlin • Boston. Source


Starcevic M.,University of Zagreb | Tomicic M.,Croatian Institute of Transfusion Medicine | Malenica M.,University of Zagreb | Zah-Matakovic V.,University of Zagreb
Acta Paediatrica, International Journal of Paediatrics | Year: 2010

Neonatal alloimmune thrombocytopenia (NAIT) occurs as a result of maternal alloimmunization against paternally inherited antigens on foetal platelets. Platelets express platelet specific antigens (HPA) along with human leucocyte antigens (HLA) class I. Although anti-HLA class I antibodies are often detectable in pregnant women, their role in NAIT is considered controversial. We report a case of NAIT where the most sensitive serological analysis and molecular methods could not detect platelet specific antibodies. Only HLA incompatibility and presence of anti-HLA-A24 antibodies in both the mother's and the newborn's serum were proven. Conclusion: This case supports the idea that some anti-HLA class I antibodies could cause NAIT. © 2009 Foundation Acta Pædiatrica. Source

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