The peculiarities of pulmonary macro- and microhemodynamics changes after treatment with agonists and blockers of cholinoceptors

Background. The pulmonary arterial and venous vessels are innervated by parasympathetic cholinergic nerves. However, the studies, performed on the isolated rings of pulmonary vessels, can not give answer to the question about the role of cholinergic mechanisms in the changes of pulmonary circulation in full measure. Aim. The comparative analysis of the changes of the pulmonary macro- and microhemodynamics after acetylcholine, atropine, pentamine and nitroglycerine treatment. Materials and methods. The study was carried out on the anesthetized rabbits in the condition of intact circulation with the measurement of the pulmonary artery pressure and flow, venae cavae flows, cardiac output, and also on isolated perfused lungs in situ with stabilized pulmonary flow with measurement of the perfused pulmonary artery pressure, capillary hydrostatic pressure, capillary filtration coefficient and calculation of the pulmonary vascular resistance, pre- and postcapillary resistances. Results. In the conditions of intact circulation after acetylcholine, pentamine and nitroglycerine treatment the pulmonary artery pressure and flow decreased, the pulmonary vascular resistance did not change as a result of decreasing of pulmonary artery flow and left atrial pressure due to diminution of venous return and venae cavaе flows. On perfused isolated lungs acetylcholine caused the increasing of pulmonary artery pressure, capillary hydrostatic pressure, pulmonary vascular resistance, pre- and postcapillary resistance and capillary filtration coefficient. After M-blocker atropine treatment the indicated above parameters of pulmonary microcirculation increased, on the contrary, after N-blocker pentamine treatment they decreased. Nitroglycerine infusion caused less decreasing of the parameters of pulmonary microcirculation in comparison with effects of pentamine, but capillary filtration coefficient decreased to a greater extent. These data indicate that nitroglycerine decreases endothelial permeability of pulmonary microvessels. Conclusion. After activation or blockade of cholinergic mechanisms in the condition of intact circulation the calculated parameter of pulmonary vascular resistance is depended from the ratio of the pulmonary artery pressure and flow and left atrial pressure, which are determined by the venous return. The different character of the changes of pulmonary microcirculatory parameters after M-blocker atropine and N-blocker pentamine treatment is evidence of reciprocal relations of M- and N-cholinoceptors in the nervous regulation of the pulmonary microcirculatory bed.

Comparative Study of Capillary Filtration Coefficient (Kfc) Determination by a Manual and Automatic Perfusion System. Step by Step Technique Review

The purpose of calculating the capillary filtration coefficient is to experimentally evaluate edema formation in models of pulmonary ischemia-reperfusion injury. For many years, the obtaining of this coefficient implies a series of manual maneuvers during ex-vivo reperfusion of pulmonary arterial pressure, venous pressure and weight, as well as the calculation of the Kfc formula. Through automation, the calculation of capillary filtration coefficient could be easier and more efficient. To describe an automatic method designed in our laboratory to calculating the capillary filtration coefficient and compare with traditional determination of capillary filtration coefficient as gold standard method. An automatic three valve perfusion system was constructed, commanded by a mastery module connected to a graphical user interface. To test its accuracy, cardiopulmonary blocks of Wistar rats were harvested and distributed in manual (n=8) and automated (n=8) capillary filtration coefficient determination groups. Physiological parameters as pulmonary arterial pressure, pulmonary venous pressure, weight and capillary filtration coefficient were obtained. Results: Capillary filtration coefficient, pulmonary arterial pressure, venous arterial pressure shown no statistical significance difference between the groups. The automated perfusion system for obtaining Kfc was standardized and validated, giving reliable results without biases and making the process more efficient in terms of time and personal staff.

Microvascular filtration is increased in the forearms of patients with breast cancer–related lymphedema

Breast cancer–related lymphedema (BCRL) is a frequent and debilitating complication of breast cancer treatment. The pathophysiology is complex and remains poorly understood; however, data suggest that changes in the peripheral circulation may contribute to edema formation. In 13 volunteers with unilateral BCRL, the following aspects of upper extremity peripheral circulation were examined: muscle relative microvascular volume; capillary filtration coefficient; central and local sympathetic vascular reflexes; skin blood flow; and forearm blood flow. These were studied via real-time, contrast-enhanced ultrasound; venous occlusion strain-gauge plethysmography; lower-body negative pressure; noninvasive blood pressure measurements; and skin 99mTc-pertechnetate clearance technique. Measurements were performed bilaterally and simultaneously in the forearms, enabling use of the nonedematous forearm as a control. Capillary filtration coefficients were additionally measured in healthy, age-matched controls. The capillary filtration coefficient was 7.98 ± 2.52 μl·100 ml−1·mmHg−1·min−1 (mean ± SD) in edematous forearms and 6.09 ± 1.83 μl·100ml·−1·mmHg−1·min−1 in nonedematous forearms in the patient group ( P < 0.001). The capillary filtration coefficient was 3.32 ± 1.17 μl·100ml−1·mmHg−1·min−1 in the forearms of healthy controls; significantly less than the both the edematous and nonedematous forearms of the patient group ( P < 0.001). No significant differences were found in muscle relative microvascular volume, forearm blood flow, skin blood flow, or central or local sympathetic vascular reflexes. Forearm microvascular filtration is increased in patients with BCRL, and more so in the edematous arm. The vascular sympathetic control mechanisms seem to be preserved. We propose that the increased capillary permeability may be due to low-grade inflammation promoted by reduced clearance of inflammatory mediators.

Diastolic function is strongly and independently associated with cardiorespiratory fitness in central obesity

Cardiorespiratory fitness [maximal O2 consumption (V̇o2max)] is an independent risk factor for type 2 diabetes; but in individuals at risk, factors influencing V̇o2max are poorly understood. We tested the hypothesis that V̇o2max is associated with diastolic function [subendocardial variability ratio (SEVR), %], as diastolic function influences myocardial perfusion. We studied 47 men and women with central obesity without diabetes. We measured fitness (V̇o2max) by treadmill testing and diastolic function (SEVR%) by pulse-wave analysis. We measured other factors influencing this relationship: insulin sensitivity [whole body glucose uptake-to-insulin concentration ratio (M/I)] by hyperinsulinemic euglycemic clamp, fatness by MR imaging and dual-energy X-ray absorptiometry, physical activity energy expenditure (metabolic equivalents of tasks) by the Sensewear Pro2 device, and muscle microvascular exchange capacity (capillary filtration coefficient) by venous plethysmography. Mean age of the subjects was 51 ± 9 (SD) yr. V̇o2max was associated with SEVR% ( r = 0.50, P = 0.001), fatness ( r = −0.39, P = 0.008), and HbA1c ( r = −0.35, P = 0.018), but not with whole body glucose uptake-to-insulin concentration ratio, metabolic equivalents of tasks, or capillary filtration coefficient. In regression modeling with age, sex, fatness, and SEVR% as explanatory variables, only age, sex, and SEVR% were independently associated with V̇o2max (SEVR% − standardized B coefficient = 0.37, 95% confidence interval = 0.003–0.18, P = 0.007). This model identified 46% of the variance in V̇o2max ( R2 = 0.46, P = 0.0001). There was a strong, independent association between V̇o2max and a measure of diastolic function in sedentary individuals with central obesity.

Isoflurane, but Not Sevoflurane, Increases Transendothelial Albumin Permeability in the Isolated Rat Lung

Background Caveolae mediated transendothelial transport of albumin has recently been shown to be the primary mechanism regulating microvascular endothelial albumin permeability. The authors investigated the effects of isoflurane and sevoflurane on pulmonary endothelial albumin permeability and assessed the potential role of the caveolae scaffold protein, caveolin-1, in these effects. Methods Isolated rat lungs and cultured rat lung microvessel endothelial cells (RLMVECs) were exposed to 1.0 or 2.0 minimum alveolar concentration (MAC) isoflurane or sevoflurane for 30 min. I-albumin permeability-surface area product and capillary filtration coefficient were determined in the isolated lungs. In RLMVECs, uptake and transendothelial transport of I-albumin were measured in the absence and presence of pretreatment with 2 mm methyl-beta-cyclodextrin, a caveolae-disrupting agent. Uptake of fluorescent-labeled albumin, as well as phosphorylation of Src kinase and caveolin-1, was also determined. In Y14F-caveolin-1 mutant (nonphosphorylatable) expressing RLMVECs, uptake of I-albumin and phosphorylation of caveolin-1 were evaluated. Results In the isolated lungs, 2.0 MAC isoflurane increased I-albumin permeability-surface area product by 48% without affecting capillary filtration coefficient. In RLMVECs, isoflurane more than doubled the uptake of I-albumin and caused a 54% increase in the transendothelial transport of I-albumin. These effects were blocked by pretreatment with methyl-beta-cyclodextrin. The isoflurane-induced increase in uptake of I-albumin in wild-type RLMVECs was abolished in the Y14F-caveolin-1 mutant expressing cells. Isoflurane also caused a twofold increase in Src and caveolin-1 phosphorylation. Neither 1.0 MAC isoflurane nor 1.0 or 2.0 MAC sevoflurane affected any index of albumin transport or phosphorylation of caveolin-1. Conclusion Isoflurane, but not sevoflurane, increased lung transendothelial albumin permeability through enhancement of caveolae-mediated albumin uptake and transport in the isolated lung. This effect may involve an enhanced phosphorylation of caveolin-1.

Transcytosis inhibitor N-ethylmaleimide increases microvascular permeability in rat muscle

N-ethylmaleimide (NEM) has been claimed to markedly inhibit the transvascular passage of small proteins and albumin by interacting with the docking and fusion of plasmalemmal vesicles with their target membranes. To investigate the role of transcytosis in the transcapillary passage of albumin, we assessed the effects of NEM on125I-labeled radioiodinated serum albumin clearance (RISA-Cl) from blood to muscle in isolated and maximally vasodilated perfused rat hindquarters, in which vascular pressures, pre- and postcapillary resistances, and the capillary filtration coefficient (CFC) were continuously monitored. NEM (0.3–0.5 mM) caused a marked increase mainly in precapillary vascular resistance. Thus the arterial-to-venous resistance ratio in NEM-treated animals was 3.12 ± 0.56 versus 1.66 ± 0.17 during the control period ( P < 0.05). Despite that, there was a doubling of both CFC from 0.0363 ± 0.0028 to 0.0778 ± 0.0101 ml · min−1 · mmHg−1 · 100 g−1 ( P < 0.01) and RISA-Cl, compared with the control situation, signaling markedly increased microvascular permeability. Our results strongly suggest that NEM, besides producing marked vasoconstriction, also causes damage to the capillary endothelium. Thus, instead of inhibiting transvascular transport, NEM may induce increases in the bulk transport of albumin from blood to tissue.