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We reported that protein kinase C (PKC) inhibitors increase the release of arachidonic acid induced by fluoroaluminate (AlF 3 4 ), an unspecific G-protein activator, in intact human platelets. Now we demonstrate that this effect is independent of the extracellular Ca 2+ concentration and that AlF 3 4 -induced release of AA is abolished by BAPTA, an intracellular Ca 2+ chelator, even in the presence of GF 109203X, a specific and potent PKC inhibitor. This compound also blocks the liberation of the secretory phospholipase A 2 in the extracellular medium, indicating that this enzyme is not involved in the potentiation of arachidonic acid by PKC inhibitors. On the other hand, the latter effect is completely abolished by treatment of platelets with AACOCF 3 , a specific inhibitor of cytosolic phospholipase A 2 (cPLA 2 ). These observations indicate that cPLA 2 is responsible for the AlF 3 4 -induced release of arachidonic acid by a mechanism that is down-regulated by PKC.z 1999 Federation of European Biochemical Societies.

Prostate adenocarcinoma PC-3 and bladder carcinoma J82 cell lines were used to investigate the role of adenosine in the modulation of cell growth. Our results show that adenosine inhibited cell proliferation in both cell lines and markedly induced apoptosis only in J82 cells. PC-3 and J82 cells showed typical sigmoid growth curves. Only the J82 growth curve was modified by the addition of adenosine deaminase, indicating that this cell line is sensitive to the presence of endogenous extracellular adenosine. Exogenous extracellular adenosine induced a dose-dependent decrease of cell growth in both cell lines. 2 0 -Deoxyadenosine and dipyridamole were used to investigate whether the growth inhibitory effect of adenosine was related to cellular uptake or to receptor-mediated action. Our results show that 2 0 -deoxyadenosine was a less effective inhibitor for J82 than PC-3 cells. Dipyridamole reduced the inhibitory effect of adenosine in both cell lines. The determination of viability associated with Hoechst staining showed that adenosine clearly induced apoptosis in J82 cell lines but was less effective in PC-3 cell lines. In conclusion, we have shown that the growth of prostate adenocarcinoma PC-3 and bladder carcinoma J82 cell lines is inhibited by adenosine and that adenosine is capable of inducing apoptosis, although to a different extent in both cell lines. Drug Dev.

Five widely used activated partial thromboplastin time (APTT) reagents (Actin-FS, Actin-FSL, Hemolab Silimat, IL-Test APTT Ellagic Acid and Thrombofax Activated) were compared for their sensitivity and precision in measuring the effect of dermatan sulphate on blood coagulation. On each of 4 days, aliquots of the same normal human plasma pool were mixed with dermatan sulphate (MF701) at concentrations ranging from 10 to 100 μg/ml, and APTT was measured in duplicate with all the reagents by a photo-optical coagulometer. The order of testing between and within reagents was changed every day. The relationship of APTT ratio to dermatan sulphate concentration was linear with all the reagents. There were statistically significant differences between reagents in their sensitivity to DS, as reflected by linear regression slopes. IL-Test was the most sensitive reagent. At dermatan sulphate concentrations of 20, 50 and 80 μg/ml APTT ratio ranged from 1.5 to 1.7, 1.9 to 2.3 and 2.3 to 2.9, respectively, according to the reagent. The lambda coefficient and coefficient of variation derived from regression analysis, both reflecting assay precision, ranged from 0.57 to 0.71 and from 4.6 to 5.1 %, respectively, with all but the least precise reagent. The best sensitivity/precision balance was displayed by IL-Test. The APTT reagent should therefore be standardized, with special regard to sensitivity to DS, when testing the relationship of dermatan sulphate clinical effects to APTT response.

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