cytochalasin-d and Edema

The increased capillary fluid filtration required to create a rapid edema formation in acute inflammation can be generated by lowering the interstitial fluid pressure (P(IF)). The lowering of P(IF) appears to involve dynamic beta(1)-integrin-mediated interactions between dermal cells and extracellular matrix fibers. The present study specifically investigates the role of the cell cytoskeleton, i.e., the contractile apparatus of cells, in controlling P(IF) in rat skin as the integrins are linked to both the cytoskeleton and the extracellular matrix. P(IF) was measured using a micropuncture technique in the dorsal skin of the hind paw at a depth of 0.2--0.5 mm and following the induction of circulatory arrest with the intravenous injection of KCl in pentobarbital anesthesia. This procedure prevented the transcapillary flux of fluid and protein leading to edema formation in acute inflammation, which in turn can increase the P(IF) and therefore potentially mask a decrease of P(IF). Control P(IF) (n = 42) averaged -0.8 +/- 0.5 (means +/- SD) mmHg. In the first group of experiments, subdermal injection of 2 microl cytochalasin D, a microfilament-disrupting drug, lowered P(IF) to an average of -2.8 +/- 0.7 mmHg within 40 min postinjection (P < 0.05 compared with control). Subdermal injection of vehicle (10% DMSO in PBS or PBS alone) did not change the P(IF) (P > 0.05). Lowering of the P(IF) was not observed after the injection of colchicine or nocodazole, which specifically disrupts microtubuli in cultured cells. In the second group of experiments, 2 microl of cytochalasin D injected subdermally into rats with intact circulation increased the total tissue water (TTW) and albumin extravasation rate (E(ALB)) by 0.7 +/- 0.2 and 0.4 +/- 0.3 ml/g dry wt, respectively (P < 0.05 compared with vehicle). Nocodazole and colchicine did not significantly alter the TTW or E(ALB) compared with the vehicle (P > 0.05). Taken together, these findings strongly suggest that the connective tissue cells can participate in control of P(IF) via the actin filament system. In addition, the observation that subdermal injection of cytochalasin D lowered P(IF) indicates that a dynamic assembly and disassembly of actin filaments also occurs in the cells of dermal tissues in vivo.

Topics: Animals; Body Water; Cytochalasin D; Edema; Extracellular Space; Female; Pressure; Rats; Serum Albumin; Skin; Skin Diseases

The purpose of this study was to examine the relationship of increased capillary network resistance due to leukocyte-capillary plugging and tissue edema through macromolecular leakage to tissue injury after ischemia-reperfusion (I/R). After a 3-h complete ischemia in the dorsal skinfold chamber of the awake Syrian hamster, the following parameters were measured: vessel diameter, macromolecular leakage, erythrocyte velocity, adherent leukocytes, rolling leukocytes, freely flowing leukocytes, functional capillary density (FCD), propidium iodide (PI)-positive cell nuclei, and increase in network flow resistance due to leukocyte-capillary plugging. These measurements were made under baseline conditions and after 0.5 and 2 h of reperfusion for I/R alone, I/R with phalloidin (PL) treatment (to block leakage), and I/R with both PL and cytochalasin D (CD) (to block both leakage and plugging). Neither treatment had an effect on the leukocyte adherence or rolling. PL treatment preserved the endothelial barrier, improved FCD, and reduced the amount of PI measured tissue damage. CD treatment eliminated the increase in network resistance due to leukocyte plugging but did not improve FCD or tissue damage. Thus, in this I/R model, macromolecular leakage plays a role in tissue injury, whereas leukocyte plugging does not appear to be an important mechanism.

Topics: Animals; Capillaries; Capillary Permeability; Cell Adhesion; Cricetinae; Cytochalasin D; Edema; Ischemia; Leukocytes; Macromolecular Substances; Male; Mesocricetus; Muscle, Skeletal; Phalloidine; Reperfusion Injury