Modulation of pulmonary permeability in vivo with agents that affect the cytoskeleton.

In vitro studies show that the cytoskeleton of the microvascular barrier moderates polymorphonuclear leukocyte (PMN) diapedesis and the transport of macromolecules. This in vivo study tests indirectly whether the cytoskeleton of the pulmonary microvasculature responds similarly to agents known to reorganize the cytoskeleton to alter diapedesis and permeability in vitro. One of four agents, saline solution, cytochalasin B (which promotes actin microfilament disassembly), leukotriene (LT) B4 (PMN chemoattractant), or phalloidin (which promotes and stabilizes F-actin polymerization) was introduced into the bronchus of the anterior segment of the left lung of anesthetized rats (n = 152) through a tracheostomy and fine-bore cannula. Twenty minutes later, saline solution, cytochalasin B, LTB4, or phalloidin was similarly introduced. PMN accumulations (x 10(4) cells/ml), protein concentration in bronchoalveolar lavage fluid, and lung wet/dry weight ratios were measured 3 hours later. When the initial and secondary treatments were saline solution, PMN accumulations were 3 +/- 1 cells/ml and the protein level was 274 +/- 48 micrograms/ml. Secondary treatment of the saline-treated group with cytochalasin B or LTB4 led to increases in PMN to 18 +/- 2 and 9 +/- 2 cells/ml and protein to 960 +/- 50 and 840 +/- 40 micrograms/ml (p less than 0.05); secondary treatment with phalloidin was similar to that with saline solution. With saline solution used for both treatments, the wet/dry ratio was 3.4 +/- 0.2. Primary saline solution and secondary treatments with either cytochalasin B or LTB4 led to a similar increase in wet/dry ratios to 3.9 +/- 0.1 (p less than 0.05), whereas phalloidin was without effect (3.5 +/- 0.3). Initial cytochalasin B treatment followed by LTB4 led to increased PMN diapedesis (43 +/- 6 cells/ml and wet/dry ratio 4.3 +/- 0.2) (p less than 0.05). Secondary phalloidin treatment attenuated the cytochalasin B effect with counts of 12 +/- 2 PMN/ml, protein levels of 460 +/- 30 micrograms/ml, and a lower wet/dry ratio of 3.7 +/- 0.1 (p less than 0.05). Even more striking, phalloidin as initial treatment further reduced the cytochalasin B effect to 7 +/- 1 PMN/ml, whereas protein level was 490 +/- 60 micrograms/ml and wet/dry ratio was 3.5 +/- 0.1 (p less than 0.05). Further, phalloidin, given initially, attenuated the effect of secondary treatment with LTB4, resulting in fewer cells (4 +/- 2 PMN/ml), a lower wet/dry ratio (3.4 +/- 0.1), and protein level of 650 +/- 20 micrograms/ml (p less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)