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Inhibition of polyamines on platelet responses
Vol. 70, Suppl. 1
ABSTRACTS OF 12TH NATIONAL CONGRESS
S27
c 038 INHIBITION OF POLYAMINES ON PLATELET RESPONSES. L. Dalla Via, M. Francesconi, ?? L. Battistella and R. Deana. Department of Biological Chemistry, University of Padova, Padova.*Centro Trasfusionale dell’ospedale di Cittadella. Italy. This study was undertaken to further elucidate the effects and the mode of action of the most important natural polyamines. i.e. spermine. spermidine and putrescine. on platelet activation induced by physiological and non physiological agonists. Spermine (l-10 mM) showed a concentration-dependent inhibition of platelet aggregation, but not of shape change. promoted by the receptor-mediated agonists thrombin (0.1 U/ml), ADP (20 PM). vasopressin (500 nM). collagen (280 &ml), and the stable thromboxane-mimetic U44069 (3 PM). In all cases a complete inhibition was obtained with 10 mM spermine. The inhibitory effect of spermidine and putrescine on thrombin or ADP-elicited platelet aggregation was much less evident than that observed with equivalent amounts of spermine. and protein Thrombin-induced cytosolic Ca2+ increase, ATP secretion phosphorylation in unstirred platelets, which occurred independently of aggregation. as well as changes of intracellular pH and membrane potential, were also drastically inhibited by spermine. By contrast 10 mM spermine inhibited partially (lo-4O?h) the aggregation induced by the direct activators of protein kinase C dioctanoylglycerol (30 PM) and phorbol ester (PMA 50 nM), by the calcium-ionophore ionomycin (0.3 FM). or by the G-protein activator fluoroaluminate (15 mM). without affecting the secretion and protein phosphorylation elicited by these compounds. A little inhibitory effect was observed on aggregation evoked by ristocetin (1.2 mg/ml). All together these results suggest a dual action of polyamines: i) a rather unspecific hindrance on the binding of agonists to the platelet membrane receptors, and ii) a weak inhibition downstream of the protein kinase C activation at a level of plateletplatelet interaction.
c 039 THE IN VITRO THROMBOXANE A2 PRODUCTION BY PLATELETS OF DIABETIC PATIEN’$S IS NORMAL AT PHYSIOLOGICAL [Ca2+]o. C, Falcon, M. Cattaneo, A. Ghidoni , P.M. Mannucci. A. Bianchi Bonomi Hemophilia and Thrombosis Center and 1st Clinical Medicine ,IRCCS Maggiore Hospital, University of Milan. Platelets of patients with DM produce normal amounts of thromboxane (TX) A2 h viva, whereas they usually show increased aggregability and TxA2 production in vitro. Since in vitro studies are usually performed in titrated PRP, we tested whether the increased TxA2 production observed in DM platelts is due to the potentiating effect of media with low [Ca2 + 1. Twenty patients with IDDM, 20 with NIDDM and 37 controls were studied. Blood was anticoagulated with 12.9 mM trisodium citrate, 0.7 mM PPACK or both. Platelt aggregation (PA), release of 14C-serotonin and TxB2 production were induced by ADP 2-4 FM, adrenaline 5 yM, collagen 2 pg/rnl or arachidonic acid (AA) 0.7 mM. Results. 1) --M PRP in citrate. AA-induced PA (p c 0.01) and TxB2 production (p < 0.002) were higher in DM patients thanjn controls; no other differences were found. 2) --PRP in PPACK: no differences btween DM patients and controls were found; 3) PRP in PPACK + citrate. results similar to those obtained with citrate were obtained. In con---d elusion, the artifactual potentiation of TxB2 production in media with low [Ca2+] accounts for the increased generation of TxB2 by DM platelets found in in vitro studies. DM platelets produce normal amounts of TxA2 in vivo and in vitro.
ABSTRACTS OF 12TH NATIONAL CONGRESS
S27
c 038 INHIBITION OF POLYAMINES ON PLATELET RESPONSES. L. Dalla Via, M. Francesconi, ?? L. Battistella and R. Deana. Department of Biological Chemistry, University of Padova, Padova.*Centro Trasfusionale dell’ospedale di Cittadella. Italy. This study was undertaken to further elucidate the effects and the mode of action of the most important natural polyamines. i.e. spermine. spermidine and putrescine. on platelet activation induced by physiological and non physiological agonists. Spermine (l-10 mM) showed a concentration-dependent inhibition of platelet aggregation, but not of shape change. promoted by the receptor-mediated agonists thrombin (0.1 U/ml), ADP (20 PM). vasopressin (500 nM). collagen (280 &ml), and the stable thromboxane-mimetic U44069 (3 PM). In all cases a complete inhibition was obtained with 10 mM spermine. The inhibitory effect of spermidine and putrescine on thrombin or ADP-elicited platelet aggregation was much less evident than that observed with equivalent amounts of spermine. and protein Thrombin-induced cytosolic Ca2+ increase, ATP secretion phosphorylation in unstirred platelets, which occurred independently of aggregation. as well as changes of intracellular pH and membrane potential, were also drastically inhibited by spermine. By contrast 10 mM spermine inhibited partially (lo-4O?h) the aggregation induced by the direct activators of protein kinase C dioctanoylglycerol (30 PM) and phorbol ester (PMA 50 nM), by the calcium-ionophore ionomycin (0.3 FM). or by the G-protein activator fluoroaluminate (15 mM). without affecting the secretion and protein phosphorylation elicited by these compounds. A little inhibitory effect was observed on aggregation evoked by ristocetin (1.2 mg/ml). All together these results suggest a dual action of polyamines: i) a rather unspecific hindrance on the binding of agonists to the platelet membrane receptors, and ii) a weak inhibition downstream of the protein kinase C activation at a level of plateletplatelet interaction.
c 039 THE IN VITRO THROMBOXANE A2 PRODUCTION BY PLATELETS OF DIABETIC PATIEN’$S IS NORMAL AT PHYSIOLOGICAL [Ca2+]o. C, Falcon, M. Cattaneo, A. Ghidoni , P.M. Mannucci. A. Bianchi Bonomi Hemophilia and Thrombosis Center and 1st Clinical Medicine ,IRCCS Maggiore Hospital, University of Milan. Platelets of patients with DM produce normal amounts of thromboxane (TX) A2 h viva, whereas they usually show increased aggregability and TxA2 production in vitro. Since in vitro studies are usually performed in titrated PRP, we tested whether the increased TxA2 production observed in DM platelts is due to the potentiating effect of media with low [Ca2 + 1. Twenty patients with IDDM, 20 with NIDDM and 37 controls were studied. Blood was anticoagulated with 12.9 mM trisodium citrate, 0.7 mM PPACK or both. Platelt aggregation (PA), release of 14C-serotonin and TxB2 production were induced by ADP 2-4 FM, adrenaline 5 yM, collagen 2 pg/rnl or arachidonic acid (AA) 0.7 mM. Results. 1) --M PRP in citrate. AA-induced PA (p c 0.01) and TxB2 production (p < 0.002) were higher in DM patients thanjn controls; no other differences were found. 2) --PRP in PPACK: no differences btween DM patients and controls were found; 3) PRP in PPACK + citrate. results similar to those obtained with citrate were obtained. In con---d elusion, the artifactual potentiation of TxB2 production in media with low [Ca2+] accounts for the increased generation of TxB2 by DM platelets found in in vitro studies. DM platelets produce normal amounts of TxA2 in vivo and in vitro.