International journal of microcirculation, clinical and experimental最新文献

The effect of hepatic nerve stimulation and norepinephrine (NE) on the laser Doppler signal from the surface of the perfused rat liver was tested. The livers from male Wistar rats were perfused in situ via the portal vein with Krebs-Henseleit buffer containing 20% bovine erythrocytes (37 degrees C, pH 7.4) and total liver blood flow (TLBF) was by timed collection of effluent. Portal vascular resistance (PVR) was calculated from the pressure difference across the liver. Linearity of laser Doppler flowmetry (LDF) with TLBF was confirmed in all preparations. Stimulation of the hepatic nerves (2 ms, 20 V) was performed at frequencies between 0.5 and 20 Hz (n = 11). NE was added to the buffer at concentrations between 10(-10) and 10(-6) M (n = 8). A stimulus-dependent rise in PVR occurred during hepatic nerve stimulation (basal, 3.11 +/- 0.26 dyn s cm-5) and NE administration (basal, 2.62 +/- 0.29 dyn s cm-5), with a maximum effect at 20 Hz (311 +/- 45%) and 10(-6) M (591 +/- 72%), respectively. Both LDF and TLBF fell during nerve stimulation and NE. A linear relationship (r = 0.99; p < 0.001) between change in TLBF (%) and LDF flux (%) was found for NE (10(-10) to 10(-6) M). During nerve stimulation, the fall in TLBF and LDF flux was linear with the logarithm of stimulus frequency and reached a maximum at 10 and 20 Hz, respectively. At a stimulus frequency of 20 Hz, the change in LDF was significantly different from the change in TLBF (p < 0.001). We conclude from our findings that during high-frequency hepatic nerve stimulation, LDF underestimates TLBF.

A growing body of evidence indicates that neutrophils play a critical role in disrupting the microvascular barrier in skeletal muscle. Recent studies from our laboratory and by others indicate that administration of antibodies directed against P-selectin, ICAM-1, or the common subunit (CD18) of CD11/CD18 was as effective as neutrophil depletion in attenuating ischemia/reperfusion (I/R)-induced microvascular barrier disruption and edema formation in skeletal muscle. These studies have important implications with regard to the pathogenesis of leg ulceration in view of our more recent work indicating that the increase in tissue pressure induced by edema formation secondary to microvascular barrier disruption may lead to the development of capillary no-reflow. The resulting maldistribution of blood flow during reperfusion exacerbates muscle injury induced by ischemia. Daflon 500 mg is a purified, micronized flavonoid fraction that exhibits a number of anti-inflammatory properties and is used clinically to treat venous insufficiency. In view of these actions and the demonstrated role of neutrophil adhesion in the pathogenesis of I/R, we sought to determine whether this agent would prevent leukocyte adhesion and microvascular barrier disruption in postischemic rat cremaster muscles and small bowel. Rats were treated with Daflon 500 mg (80 mg/kg/day by gavage) or its vehicle for 2 (cremaster studies) or 10 (mesenteric studies) days prior to the experiments. Leukocyte/endothelial cell interactions and venular protein leakage were quantitated using intravital microscopic techniques in rat cremaster muscles and mesenteries subjected to ischemia (60 min for cremaster, 20 min for mesentery) and reperfusion (60 min). The results indicated that Daflon 500 mg was as effective as the anti-adhesive monoclonal antibodies in reducing postischemic leukocyte adhesion and emigration and venular protein leakage in these models.

The currently favoured hypothesis for the link between the raised venous pressure of chronic venous insufficiency and venous ulceration is based on the intermittent inappropriate activation of white blood cells. The damage initiated by the oxidative burst of the leucocyte leads to endothelial dysfunction, interstitial oedema, microthrombi and long-term microcirculatory damage including decreased capillary density. The net result is impairment of the potential for healing and hence ulceration.

We have recently shown that the purified micronized flavonoid fraction (90% diosmin and 10% hesperidin) Daflon 500 mg attenuates reperfusion injury in the striated skin muscle of the hamster. Herein, we report on the action of Daflon 500 mg on postischemic macromolecular leakage of FITC-dextran 150 kD provoked by tourniquet ischemia. Intravital fluorescence microscopy was used for analysis of macromolecular leakage in the microcirculation model of the hamster. A tourniquet ischemia of 4 h duration was induced followed by reperfusion. Animals were treated by gavage of Daflon 500 mg (n = 6) for 8 days at a daily dose of 30 mg kg(-1) body weight. Control animals received equivalent volumes of the vehicle (5% Arabic gum solution, n = 6). Measurements of the microcirculatory parameters were made before induction of ischemia and at 0.5, 2 and 24 h of reperfusion. After induction of ischemia, macromolecular leakage from postcapillary venules was significantly enhanced in vehicle-treated animals. Treatment with Daflon 500 mg significantly attenuated macromolecular leakage of FITC-dextran 150 kD. Preliminary data from a histomorphometric analysis (n = 3/experimental group) indicated that the number of emigrated (extravascular) leukocytes after ischemia reperfusion was markedly reduced in Daflon 500 mg-treated animals as compared to controls. These data indicate that Daflon 500 mg prevents leakage of the macromolecular tracer FITC-dextran 150 kD from postcapillary venules after postischemic reperfusion, presumably through an inhibitory action on the emigration of activated leukocytes.

A small-bowel manometry tube was supplied with two single-fiber microprobes, which recorded blood flow in the proximal small intestine by the laser-Doppler flowmetry (LDF) technique. In all experiments, saline was infused intravenously as control during the first migrating motor complex (MMC) cycle, and a drug or another saline control given intravenously during the second MMC cycle. Recordings were performed during phase 1 of MMC, i.e. when motor pattern showed quiescence. Adrenaline increased blood perfusion values by 140% in proximal duodenum and 95% in distal duodenum. The alpha 2-adrenoceptor agonist clonidine decreased the corresponding values by 34 and 25%, respectively, while oxymetazoline decreased perfusion by 33 and 44% at the same levels. The beta-adrenoceptor agonist isoprenaline increased blood perfusion values by 172% in the proximal duodenum and 194% in the distal duodenum, whereas the antagonist propranolol decreased the corresponding values by 45 and 52%, respectively. In a separate group of subjects, propranolol was given after adrenaline. The increase in blood perfusion regularly seen after adrenaline was blocked after propranolol administration. In conclusion, our findings validate semi-invasive LDF technique for studies of hemodynamics in human small intestine under basal motor conditions and in drug-induced blood flow changes.

We have measured the plantar forefoot skin circulation by the uptake of sodium fluorescein (fluorescein flowmetry), 133Xe clearance and laser Doppler fluxmetry in 24 healthy subjects and correlated measurements under basal conditions and after provocation by alcohol intake and application of external heat. To assess the change in skin circulation between the initial measurement at rest and the second measurement after provocation, the coefficient of correlation (r) of the fluorescein flowmetry to the fast slope of the 133Xe elimination curve was 0.46 (p < 0.05), to the slow slope of the 133Xe elimination curve 0.66 (p < 0.001) and to laser Doppler fluxmetry 0.86 (p < 0.001). The coefficient of correlation (r) of the fluorescence appearance time to fluorescein flowmetry was 0.65 (p < 0.001), to the fast slope of the 133Xe elimination curve 0.14 (p = 0.42), to the slow slope of the 133Xe elimination curve 0.47 (p < 0.05) and to laser Doppler fluxmetry 0.63 (p < 0.001). The uptake of sodium fluorescein as measured by fluorescein fluxmetry correlates well with both 133Xe clearance and laser Doppler fluxmetry in assessing a change in skin circulation in healthy humans. The fluorescence appearance time also correlates to the slow slope of the 133Xe elimination curve and to laser Doppler fluxmetry though to a lesser extent.