Sigma Alb Research Articles

Pulmonary vascular permeability and ischemic injury in gelsolin-deficient mice.

Gelsolin is a potent actin filament regulatory protein that controls cytoskeletal assembly and disassembly. Because cellular gelsolin deficiency leads to pronounced actin stress fiber formation and defective chemotaxis, and similar cytoskeletal remodeling results in endothelial barrier dysfunction, we hypothesized that gelsolin deficient mice would exhibit increased vascular permeability. To test this hypothesis, we compared baseline lung lavage (BAL) protein concentration, wet/dry weight ratio, and osmotic reflection coefficient for albumin (sigma alb) in gelsolin-deficient (gsn-/-) and C57BL/6 (wild-type) mice. In addition, we assessed lung permeability in response to ischemia by evaluating BAL protein concentration after 4, 8, or 24 h of left pulmonary arterial (LPA) occlusion, and lung wet/dry weight ratio and histology after 24 h of LPA occlusion, in gsn-/- and wild-type animals, as compared with control and sham-operated mice. Baseline measurements revealed that BAL protein concentration was 18-fold higher in gsn-/- than in wild-type mice, whereas sigma alb averaged 0.62 + 0.15 in wild-type, as compared with 0.31 + 0.05 in gsn-/- animals, indicating that gelsolin deficiency caused increased pulmonary vascular permeability. Ischemia increased lung permeability (BAL protein and lung wet/dry weight) in both wild-type and gsn-/- mice. However, whereas the fold-increase in BAL protein concentration was less in gsn-/- mice (2- to 4-fold) as compared with wild-type (22- to 34-fold), the duration of ischemia-induced permeability changes was prolonged. Lung wet/dry weight and gross histology following ischemia were comparable in wild-type and gsn-/- animals. These data suggest that gelsolin significantly contributes to maintenance of vascular barrier function in the lung.

Vascular injury in isolated sheep lungs. Role of ischemia, extracorporeal perfusion, and oxygen.

Extracorporeal perfusion of isolated sheep lungs with blood after 30 min of ischemia caused injury manifested by polymorphonuclear (PMN) leukocyte sequestration, pulmonary hypertension, thromboxane release, and increased pulmonary vascular permeability. To determine the roles of ischemia, extracorporeal perfusion, and oxygen in this injury, lungs ventilated with 28% O2-5% CO2 and subjected to 30 min of ischemia followed by 180 min of perfusion (ischemic-perfused, n = 23) were compared with lungs subjected to (1) ischemia without perfusion (ischemic, n = 7), (2) perfusion without ischemia (perfused, n = 20), or (3) both ischemia and perfusion during ventilation with 95% N2 (anoxic ischemic-perfused, n = 15). Compared with ischemic-perfused lungs, ischemic lungs had an increased reflection coefficient for albumin (sigma alb, 0.82 +/- 0.03 versus 0.54 +/- 0.05) and decreased filtration coefficient (Kf, 0.05 +/- 0.01 versus 0.11 +/- 0.03 g.min-1.mm Hg-1.100 g-1). Perfused lungs had increased pulmonary hypertension, lung PMN leukocytes, and sigma alb (0.74 +/- 0.05); Kf was not different. Anoxic ischemic-perfused lungs had decreased pulmonary hypertension and thromboxane release, but sigma alb and Kf were not altered. These results suggest that extracorporeal perfusion caused PMN leukocyte sequestration, thromboxane release, and pulmonary hypertension, whereas ischemia caused derecruitment of vascular surface area. Injury required both ischemia and perfusion, but it was not decreased by anoxia, suggesting that oxygen radicals were not involved.

Effects of oxygen tension and glucose concentration on ischemic injury in ventilated ferret lungs.

In the ventilated ischemic lung, oxygen tension will increase at a time when glucose depletion may impair antioxidant defenses, thereby predisposing the lung to injury mediated by oxygen radicals. In the unventilated ischemic lung, however, glucose depletion in the setting of low oxygen tension may decrease production of ATP, leading to injury by a different mechanism. In this study, we evaluated the role of both oxygen tension and glucose concentration on ischemic injury in isolated ferret lungs. Injury, defined as an increase in vascular permeability, was assessed by measurement of filtration coefficient (Kf) and osmotic reflection coefficient for albumin (sigma alb) after 3 h of normothermic (37 degrees C) ischemia without reperfusion. Lungs were ventilated with either 95% O2-5% CO2 or 0% O2-5% CO2. The vasculature was flushed with physiological salt solution containing either 15 mM glucose (hyperoxia-glucose, anoxia-glucose), 15 mM sucrose (hyperoxia-sucrose, anoxia-sucrose), or no substrate (hyperoxia-no substrate, anoxia-no substrate) (n = 6 for each condition). Kf and sigma alb in hyperoxia-no substrate group did not differ from values in minimally ischemic normoxic normoglycemic ferret lungs. Without glucose, ischemic injury was worse in anoxic than in hyperoxic lungs. With glucose, ischemic injury was worse in hyperoxic than in anoxic lungs. Glucose exacerbated injury in hyperoxic, but not anoxic, lungs. These results indicate that ischemic injury in these lungs depended on both oxygen tension and glucose concentration and suggest that both oxygen radical generation and ATP depletion during ischemia may contribute to the development of this injury.

Separate effects of ischemia and reperfusion on vascular permeability in ventilated ferret lungs.

In systemic organs, ischemia-reperfusion injury is thought to occur during reperfusion, when oxygen is reintroduced to hypoxic ischemic tissue. In contrast, the ventilated lung may be more susceptible to injury during ischemia, before reperfusion, because oxygen tension will be high during ischemia and decrease with reperfusion. To evaluate this possibility, we compared the effects of hyperoxic ischemia alone and hyperoxic ischemia with normoxic reperfusion on vascular permeability in isolated ferret lungs. Permeability was estimated by measurement of filtration coefficient (Kf) and osmotic reflection coefficient for albumin (sigma alb), using methods that did not require reperfusion to make these measurements. Kf and sigma alb in control lungs (n = 5), which were ventilated with 14% O2-5% CO2 after minimal (15 +/- 1 min) ischemia, averaged 0.033 +/- 0.004 g.min-1.mmHg-1.100 g-1 and 0.69 +/- 0.07, respectively. These values did not differ from those reported in normal in vivo lungs of other species. The effects of short (54 +/- 9 min, n = 10) and long (180 min, n = 7) ischemia were evaluated in lungs ventilated with 95% O2-5% CO2. Kf and sigma alb did not change after short ischemia (Kf = 0.051 +/- 0.006 g.min-1.mmHg-1.100 g-1, sigma alb = 0.69 +/- 0.07) but increased significantly after long ischemia (Kf = 0.233 +/- 0.049 g.min-1 x mmHg-1 x 100 g-1, sigma alb = 0.36 +/- 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Segmental barrier properties of the pulmonary microvascular bed

We determined liquid flux across single pulmonary microvessels of dog, ferret, and rat by our split-drop technique (J. Appl. Physiol. 64: 2562-2567, 1988). Data are reported from 58 lungs excised under halothane or pentobarbital sodium anesthesia and then blood perfused. We stopped blood flow at known vascular pressures and then micropunctured microvessels to inject oil, which we split with albumin solution. From measurements of vessel diameter and split oil drop length, we calculated Jv, the liquid transport rate per unit surface area [x 10(-6) ml/(cm2.s)]. At constant vascular pressure, Jv was not significantly different after different periods of oil-endothelium contact and at different sites within a single vessel. From measurements of Jv at different vascular pressures, we determined Lp, the hydraulic conductivity [x 10(-7) ml/(cm2.s.cmH2O)], and Pzf, the zero filtration pressure. From determinations of Pzf at different albumin concentrations, we quantified sigma alb, the albumin reflection coefficient. Lp and Pzf did not differ among venules of the same lung. However, in venules, Lp was 40% higher and sigma alb 25% lower than in arterioles (P less than 0.01). We conclude that 1) micropuncture procedures incidental to our split-drop technique do not progressively deteriorate the experimental microvessel and 2) in lung, permeability is higher in venules than in arterioles.

Transcapillary transport during secretion by the rabbit submandibular salivary gland.

Fluid exchange in the rabbit submandibular gland has been studied with a view to improving understanding of the mechanisms underlying transcapillary transport during salivation. Using maximally vasodilated glands perfused in vitro, we found that acetylcholine had no significant effect on either hydraulic conductance (filtration coefficient, Lp) or reflection coefficient to albumin (sigma alb) of the gland microvessels. In vivo, parasympathetic nerve stimulation increased blood flow 20-fold, interstitial fluid production (total fluid efflux - saliva flow) increased approximately 10-fold, while filtration fraction remained constant. At the same time, isogravimetric capillary pressure increased about six-fold. There are several possible explanations for these findings, and it is argued that they are likely to include capillary recruitment. Thus, during salivation, parasympathetic nerve stimulation does not lead to a change in capillary permeability as such, but rather produces a relaxation of resistance vessels and a fall in precapillary resistance, accompanied by an increase in available capillary surface area. This leads to a rise in capillary blood flow and pressure, which in turn increase fluid filtration. These changes are self-limiting due to the resulting dilution of interstitial protein and rise in interstitial pressure, but during salivation, since the secretion is pumped out of the interstitium, this fluid transport has no net effect on transcapillary gradients.