B Arnoux’s research while affiliated with Centre Hospitalier Universitaire de Limoges and other places

The origin of the thrombocytopenia and leucopenia induced by protamine-heparin complexes is unknown. We studied the biochemical and cellular effects of protamine (6 mg x kg-1, i.v.) injected after heparin (5 mg x kg-1, i.v.) in New Zealand rabbits. After protamine injection (0.5 min) increases in blood platelet-activating factor (PAF-acether, PAF) (27.6 +/- 27.6 to 148.2 +/- 48.9 pg x ml-1, P < 0.05), thrombocytopenia (403 +/- 64 to 166 +/- 13 cells x 10(-3) x mm-3, P < 0.05) and leucopenia (7650 +/- 930 to 4300 +/- 668 cells x mm-3, P < 0.05) were noted. Plasma thromboxane B2 increased at 1 min (125.6 +/- 24.4 to 879.7 +/- 141.0 pg x ml-1, P < 0.01). Protamine alone induced no change. Indomethacin (3 mg x kg-1, i.v.) did not counteract the effects of heparin-protamine. Pretreatment with the PAF receptor antagonist BN 52021 [9H1, 7a-(epoxymethano)-1 H,6aH-cyclopenta[c]furo[2,3-b]furo-[3',2',3,4]cyclopenta[1,2-d]fur an-5,9, 12(4H)trione,3-tert-butylhexahydro-4,7b,11 hydroxy-8 methyl] alone (3 mg x kg-1, i.v.) delayed thrombocytopenia and reduced plasma thromboxane B2 concentration but did not modify leucopenia. Thus thrombocytopenia and thromboxane B2 release triggered by heparin-protamine may be potentiated by the release of PAF.

To assess after cardiopulmonary bypass (CPB) the role of paf-acether (paf), a phospholipid mediator whose injection in animal mimics the hemodynamics observed after CPB. Prospective double-blind randomized study. Single institutional university hospital. 18 patients scheduled to undergo coronary artery bypass graft. 18 patients randomly received a placebo (n = 8) or 120 mg BN52021 (n = 10), a paf-receptor antagonist injected twice just before vascular cannulation and before cross-clamp release. Hemodynamic measurements were performed with a pulmonary artery and a radial artery catheter before and after the first injection of BN52021 or placebo, at the end of CPB, 1, 15, and 30 minutes after protamine infusion, then 6 hours and 24 hours postoperatively. BN52021 infusion, did not affect hemodynamic parameters. After CPB, the pulmonary artery pressures, the cardiac index, and the pulmonary artery occlusion pressures were statistically the same between groups. By contrast, the pulmonary vascular resistances (1.5 +/- 0.5 IU v 4.5 +/- 0.6 IU, p < 0.05), the right ventricular systolic work index (5.3 +/- 0.91 g m m-2 v 9.37 +/- 1.02 g m m-2, p < 0.05) and the transpulmonary gradient (4.7 +/- 1.1 mmHg v 12.0 +/- 1.2 mmHg, p < 0.05) were lower in the BN52021 group as compared with the placebo group. After protamine infusion, these differences between groups disappeared. Because the inotropic and vasodilator therapy and the volume loading were the same between groups, this study suggests that pretreatment with a paf-receptor antagonist improves post-CPB pulmonary resistance. Nevertheless, this beneficial effect is transient without consequences on left ventricular function indices.

PAF-acether is a phospholipid synthesized by most animal tissues and exerting a strong decrease on the heart's contractile force and coronary flow. PAF-acether (10(-9) and 10(-10)M) was administered to isolated guinea pig hearts perfused via the Langendorff apparatus with Chenoweth solution. Zinc (1.5 microM) is known to benefit heart function thus, Zn2+ (1.5, 7.5, and 30 microM) was added in the perfusing solution before or after PAF-acether administration. Contractile force, coronary flow, and heart rate were recorded by means of a Narco MK-IV Physiograph throughout all modes of perfusion. Calcium inhibitor (Verapamil 10(-10)M) and Pb+2 Co2+ (1.5 x 10(-6)M) were used subsequently in the perfusing solutions in order to elucidate some of the Zn and PAF interactions observed. All hearts were analyzed for their Zn and Ca content by means of an Atomic Absorption Spectrophotometry (AAS). Our data suggest that low concentrations of zinc (1.5 microM) can strongly inhibit PAF-induced decrease of contractile force and coronary flow. Zinc-inhibiting effects on PAF's negative inotropic action (myocytic level) is not exerted through Zn-Ca antagonism. Nevertheless, a Zn-Ca antagonism in the arteriolar level cannot be excluded. Zinc inhibits PAF selectively only if it is administered before PAF injection and this strongly suggests a receptor interaction between the metal and the phospholipid at the heart level.

To evaluate the role of platelet activating factor (PAF) in the early stage of arthritis. Arthritis was induced in rabbits by weekly intra-articular injections of carrageenan. A PAF receptor antagonist, BN 50730, was used as a preventive or curative agent. BN 50730 was able partially to prevent the development of arthritis, and was also active on established arthritis. The joint arthritis scores of BN treated animals were significantly lower than those of the non-treated animals. The blood concentrations of PAF, PAF bound to lipoproteins (lipo-PAF), and its precursor, lyso-PAF, were not correlated with clinical variations. The present data demonstrate a therapeutic action of a PAF antagonist in experimental arthritis and suggest a critical role for PAF during the early stage of arthritis.

Cardiopulmonary bypass (CPB)-induced thrombocytopenia and leukopenia is augmented after heparin reversal of protamine. Platelet-activating factor (PAF) might be implicated in these disorders. To evaluate the effects of PAF on the hematologic disorders and blood loss during and after CPB, patients were pretreated with BN 52021, a PAF receptor antagonist, or a placebo. BN 52021 (120 mg) (n = 13) or placebo (n = 15) were infused intravenously before vascular cannulation and before cross-clamp release. Platelet and leukocyte counts were assessed in venous blood before and after the first dose of BN 52021 or placebo, 2 min after the beginning of CPB (at the entry of the oxygenator), at the end of CPB, 1, 15, and 30 min after protamine infusion, and 6 and 24 h after CPB. The decrease in platelet and leukocyte counts were the same between groups during and after CPB and after protamine infusion. Bleeding times were not modified by the pretreatment of patients with BN 52021. During surgery, blood loss reached 1660 +/- 297 mL in the BN 52021 group and 1599 +/- 283 mL in the placebo group (P > 0.05). Forty-eight hours postoperatively, the chest tube outputs were not different between groups (1460 +/- 418 mL vs 1640 +/- 362 mL in the BN 52021 and placebo groups, respectively). This study shows that BN 52021 infusion did not change the hematologic variables studied. Moreover, a PAF antagonist pretreatment did not protect the patients against CPB- or protamine-induced hematologic changes.

Isolated guinea pig hearts were perfused, by the Langendorff technique, with 30, 15, 7.5, and 1.5 μM Zn2+ in Chenoweth solution. Contractile force, coronary flow, and heart rate were recorded by means of Narco IV Physiograph. Calcium inhibitor (Verapamil 1 μM) and anion inhibitor (DIDS: 0.1, 1, and 5 μM) were used subsequently in the perfusing solutions in order to distinguish some of the possible mechanisms that Zn2+ uses to exert its action on cardiac myocytes. Isomolar to zinc concentration of Pb (II) and Co (II) were used to elucidate whether zinc effects on heart are specific for this metal. All hearts were used to estimate their zinc and calcium content by means of AAS (Atomic Absorption Spectrometry). Our findings suggest that the higher the Zn2+ concentration, the more toxic effects on heart are expressed by rapid reversible contractile force reduction and reversible specific changes of heart rate and flow. Zinc 1.5 μM in the perfusing solution benefits heart performance, but not significantly. Furthermore, the metal exerts specific effects on guinea pig heart, and it is rather possible that these effects on cardiac myocytes are held through cell membrane receptors.

Extracorporeal circulation (ECC) is associated with thrombocytopenia and transient leukopenia. After ECC and coronary artery bypass graft (CABG) surgery, some patients can develop pulmonary and cardiac dysfunction, which might be related to the release of various mediators such as thromboxane A2, C5a, and C3a anaphylatoxins. The involvement of PAF-acether (PAF), a potent vasoactive thrombocytopenic and leukoneutropenic agent, has not been determined. Therefore, 10 patients were studied during and after CABG. The release of PAF, lipo PAF (PAF bound to blood lipoproteins), and lyso PAF (PAF precursor and metabolite) was measured in blood from the left atrium, radial artery, and pulmonary artery before and after CABG. PAF, lipo PAF, and lyso PAF were also determined during ECC at the entry and exit points of the oxygenator. Hemodynamic parameters, platelet, and leukocyte counts in the pulmonary artery were measured simultaneously. PAF did not increase significantly during ECC; it showed a transitory six-fold increase immediately after CABG in the radial artery (0.18 +/- 0.13 v 1.09 +/- 0.36 ng/mL, P < 0.05), but not in the pulmonary artery (0.10 +/- 0.03 v 0.56 +/- 0.21 ng/mL, P > 0.05). Blood PAF amounts in the radial artery were significantly higher than in the left atrium following ECC (1.09 +/- 0.36 v 0.06 +/- 0.04, P < 0.05), probably indicating PAF production in the heart. No variation of blood lipo PAF and lyso PAF was observed. No correlation was seen between PAF amounts and blood cell count.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of protamine (6 mg kg-1) injected after heparin (5 mg kg-1) have been studied in five groups of five New Zealand white rabbits. Group I was treated with the sequence heparin-protamine and group II with protamine alone. The animals of groups III and IV received respectively intravenous indomethacin (3 mg kg-1) and BN 52021 (3 mg kg-1), a paf receptor antagonist before the sequence heparin-protamine. Group V was pre-treated with indomethacin and BN 52021 before heparin reversal with protamine. In group I, immediate thrombocytopenia (44.1 +/- 4.6% of baseline level, P less than 0.05) and leucopenia (55.5 +/- 2.3% of baseline level, P less than 0.05) were observed 30 s after protamine reversal of heparin, paralleled with an increase in blood paf levels (27.6 +/- 27.6 vs. 148.2 +/- 48.9 pg ml-1, P less than 0.05). In group II, protamine alone induced no change in platelet count nor in blood paf levels (55 +/- 10 vs. 52.5 +/- 20 pg ml-1, P greater than 0.05). Pre-treatment with indomethacin alone (group III) did not protect the animals against the haematological changes induced by the heparin-protamine complexes. Pre-treatment with the paf receptor antagonist, alone or in association with indomethacin, delayed the occurrence of thrombocytopenia 3 min after protamine administration but the leucopenia was the same as in group I. This study demonstrated that paf is implicated in the immediate thrombocytopenia occurring after protamine reversal of heparin in rabbit.

The potent inflammatory mediator PAF-acether (PAF = platelet-activating factor) can produce the same hemodynamic and hematological effects as protamine infusion. In 10 patients, blood PAF and precursor levels were measured in the left atrium, the pulmonary and the radial artery before and after protamine reversal of heparin during coronary artery bypass graft. Blood PAF level in the left atrium increased 6-fold (17 +/- 12 pg.ml-1 vs 98 +/- 46 pg.ml-1, P = 0.03) after protamine infusion. By contrast, a 4-fold decrease was observed in the pulmonary artery blood (130 +/- 48 pg.ml-1 vs 31 +/- 23 pg.ml-1, P = 0.03) and a 9-fold decrease was noted in the radial artery blood (285 +/- 104 pg.ml-1 vs 31 +/- 15 pg.ml-1, P = 0.01). No cardiovascular impairment was observed but all patients exhibited thrombocytopenia. After protamine, PAF in the left atrium reached lower levels than those observed in the pulmonary and radial artery before protamine infusion. Moreover, no significant correlation was observed between platelet counts and PAF levels. Thus PAF seems not to mediate the platelet drop induced by heparin-protamine complexes. A positive correlation was obtained between leukocyte counts in the pulmonary artery and PAF levels in the left atrium (r = 0.78, P = 0.02). Protamine infusion may stimulate PAF biosynthesis by leukocytes in the lung, on the one hand, and accelerate the disappearance of PAF in the arterial bed, on the other hand.