Thiamylal and Pentobarbital Have Opposite Effects on Human Platelet Aggregation In Vitro

Phospholipase Cγ2 signalling contributes to the haemostatic effect of Notoginsenoside Ft1

OBJECTIVES

The drawback of bleeding caused by chronic antiplatelet therapy is persecuting patients with thrombotic diseases severely. Based on the dual-directional regulatory effect of Panax notoginseng on platelet, the present study focused on the effect of Notoginsenoside Ft1, a saponin with effect in promoting platelet aggregation.

KEY FINDINGS

According to the present study, Notoginsenoside Ft1 cannot stimulate platelet aggregation independently. However, the effect in enhancing aggregation induced by thrombin, collagen and ADP is peaked at 5-10 μm. In addition, thrombin-induced activation of PLCγ2-IP₃ /DAG-[Ca²⁺ ]/PKC-TXA₂ signalling was potentiated by Notoginsenoside Ft1, as well. Furthermore, the mice tail bleeding time was shortened by administration of Notoginsenoside Ft1 significantly. And the bleeding time prolonged by aspirin was also restored by Ft1.

CONCLUSIONS

The haemostatic effect of Notoginsenoside Ft1 was exerted through potentiation of PLCγ2-IP₃ /DAG-[Ca²⁺ ]/PKC-TXA₂ signalling pathway stimulated by other stimulators. Notoginsenoside Ft1 has the potential to be developed into supplements in antiplatelet therapy to prevent the drawback of bleeding.

Anesthetic technique does not affect the performance of a rabbit model of arterial cyclic flow reductions: a pilot study

PURPOSE

Pentobarbital anesthesia is, typically, used in an experimental model of cyclic flow reductions (CFR) in rabbits. Our initial observations, using a more complete and effective isoflurane-based anesthetic technique, failed to reproduce findings reported previously. Consequently, we compared the effects of these two anesthetic techniques in the model.

METHODS

A modified Folts' model of carotid artery lesion and stenosis was used. Twelve rabbits completed the experimental protocol: five in the pentobarbital group (P) and seven in the isoflurane group (I). The carotid artery was exposed and flow was reduced by application of a clamp. A standardized injury was performed by cross clamping the artery with a needle forceps and this produced CFR. The number of CFR and the duration of their occurrence were noted. The incidence of thrombosis was compared in each group as well as hemodynamic, hematologic and bleeding time values.

RESULTS

The hematocrit value, platelet count and bleeding time were similar in both groups. The median number and range of CFR [group P: 9 (4-16) ; group I: 9 (5-14)] and the time span of effective CFR formation (group P: 39 +/- 17; group I: 38 +/- 25 min) were comparable in both groups. The incidence of complete thrombosis of the carotid artery was similar in both groups.

CONCLUSIONS

The stability of the model is of short duration, but the occurrence of CFR is not affected by the type of anesthesia. Our findings suggest that the ideal duration of the experimental protocol should be between 30 and 45 min in order to maximize the number of animals still developing CFR.

Differential effects of intravenous anesthetics on ciliary motility in cultured rat tracheal epithelial cells

PURPOSE

It has been shown that airway ciliary function is impaired by several anesthetic or sedative drugs, which may predispose anesthetized or intensive care patients to respiratory complications, such as hypoxemia, atelectasis and pulmonary infection. We studied the effects of midazolam, propofol, dexmedetomidine, ketamine, fentanyl, thiopental and pentobarbital on ciliary beat frequency (CBF) in isolated and cultured rat tracheal epithelial (RTE) cells, to investigate their direct CBF action removing influences of non-epithelial cells.

METHODS

Rat tracheal epithelial cells were purely isolated from tracheas of adult male Sprague-Dawley rats. After 14 to 21 days of culture, the images of motile cilia were videotaped using a phase-contrast microscope. Baseline CBF and CBF 30 or 50 min after administration of vehicle or one of the above agents were computer-analyzed.

RESULTS

Midazolam (0.3-10 microM), propofol (1-100 microM), dexmedetomidine (1-100 nM), fentanyl (0.1-10 nM) and thiopental (30-300 microM) had no effect on CBF. Ketamine at a supraclinical dose (1000 microM) increased CBF (22 +/- 13, mean +/- standard deviation, % increase from baseline; baseline = 100%) significantly (P < 0.01). Fentanyl at a high clinical dose (100 nM) increased CBF significantly (10 +/- 9%). Pentobarbital decreased CBF dose-dependently (100 microM, -2 +/- 6%; 300 microM, -14 +/- 18%; 1000 microM, -75 +/- 5%) and reversibly (P < 0.01).

CONCLUSION

These results show that midazolam, propofol, dexmedetomidine and thiopental have no direct action on CBF in isolated RTE cells, whereas high doses of ketamine and fentanyl have direct ciliostimulatory actions and pentobarbital has a direct cilioinhibitory action.

Inhibitory effects of cardiotonic pills on platelet function in dogs fed a high-fat diet

Insulin resistance and the consequent metabolic disorders are associated with a state of platelet hyperactivity. Oxidative stress is responsible for the persistent platelet activation. We sought to study the inhibitory effect of cardiotonic pills, an oral herbal component, on platelet function in a dog model with insulin resistance induced by high-fat feeding. We fed 18 dogs with a high-fat diet and six dogs with normal chow as control for 6 months. Then, six dogs were fed with a high-fat diet and received additional aspirin (250 mg/day), and another six dogs received additional cardiotonic pills (1,000 mg/day) for 4 months. Time-course changes in metabolic parameters and platelet function were detected. After high-fat feeding for 6 months, 18 dogs developed a series of metabolic disorders including obesity, dyslipidemia, oxidative stress and insulin resistance. In addition, a platelet hyperactivity state, characterized by increased agonist (arachidonic acid, ADP and collagen) induced platelet aggregation, platelet expression of adhesion molecules (P-selectin and GP IIb/IIIa), and platelet intracellular calcium concentration, was indicated. Cardiotonic pills showed a significant antioxidative activity by presenting an increase in plasma superoxide dismutase and decrease in erythrocyte glutathione, as well as a lipid-lowering effect (decrease in both plasma cholesterol and triglyceride). Either aspirin or cardiotonic pills could significantly reverse the platelet hypersensitivity and hyperfunction. Compared with aspirin, cardiotonic pills showed a more exaggerated inhibitory effect on platelet function (a significantly decreased collagen-stimulated platelet aggregation, and expression of adhesion molecules). In conclusion, cardiotonic pills inhibited platelet hyperfunction in dogs with insulin resistance. This inhibitory effect may mainly be explained by antioxidative activity and metabolic control.