Three surface-active fractions which differ in their morphology have been isolated from rat lung homogenates by ultracentrifugation in a discontinuous sucrose density gradient . In order of increasing density, the fractions consisted, as shown by electron microscopy, primarily of common myelin figures, lamellar bodies, and tubular myelin figures . The lipid of all three fractions contained approximately 94% polar lipids and 2 % cholesterol . In the case of the common myelin figures and the lamellar bodies, the polar lipids consisted of 73% phosphatidylcholines, 9 % phosphatidylserines and inositols, and 8 % phosphatidylethanolamines. In the case of the tubular myelin figures, the respective percentages were 58, 19, and 5 . Over 90% of the fatty acids of the lecithins of all three fractions were saturated . Electrophoresis of the proteins of the fractions in sodium dodecyl sulfate or Triton X-100 revealed that the lamellar bodies and the tubular myelin figures differed in the mobilities of their proteins . The common myelin figures, however, contained proteins from both of the other fractions. These data indicate that, whereas the lipids of the extracellular, alveolar surfactant(s) originate in the lamellar bodies, the proteins arise from another source . It is further postulated that the tubular myelin figures represent a liquid crystalline state of the alveolar surface-active lipoproteins.

We propose that the surface-active lining of the mammalian lung is formed in the mitochondria of the alveolar epithelial cells. Findings supporting this hypothesis are the presence of strong surfactant uniquely in the washed mitochondrial fraction of mammalian lung, almost complete loss of mitochondrial lamellar forms accompanying loss of lung surface activity after vagotomy, and the absence of strong surface activity from the lung extracts of animals whose alveolar lining cells show no lamellar forms.

We hypothesized that xanthine oxidase (XO)-derived hydrogen peroxide (H2O2) contributes to ischemic skeletal muscle injury during reperfusion. We found that after ischemia (3 h) and then reperfusion (4 h) rat gastrocnemius muscles had decreased contractile function following direct stimulation. Three lines of investigation suggested that XO-derived H2O2 contributes to reperfusion injury of ischemic skeletal muscle. First, treatment with dimethylthiurea (DMTU), a highly permeant O2 metabolite scavenger, but not urea, just before reperfusion improved muscle function in legs subjected to ischemia and then reperfusion. Second, gastrocnemius muscles from rats fed tungsten or allopurinol had negligible XO activities and increased muscle function after ischemia and reperfusion. Third, as assessed by measurement of skeletal muscle catalase activity in the presence of aminotriazole, H2O2 was measured during reperfusion of ischemic muscles from untreated or urea-treated rats but not during reperfusion of muscles from rats treated with DMTU, tungsten, or allopurinol.

Impairment of cardiac contractile function is an important component of acetate associated hypotension during hemodialysis treatments. We examined the effect of acetate on cardiac energy metabolism using the isovolumic isolated perfused heart model. In this preparation, acetate (10 M) caused decreases in tissue ATP concentrations (12.3 +/- 0.8 vs. 15.6 +/- 1.0 micromol/g dry at 30 min, P < 0.05) as well as marked impairment of systolic function (dpdt = 863 +/- 135 vs. 1288 +/- 166 mm Hg/second at 30 min, P < 0.05). Although altering perfusate calcium concentrations (0.6, 1.2 and 2.4 mM) affected physiological responses to acetate (5 and 10 mM), the reductions in tissue ATP concentrations were similar. In isolated heart mitochondria, acetate (100 microM -10 mM) selectively impaired octanoate and palmityl carnitine supported State 3 respiration in a dose dependent fashion (P < 0.01), but did not affect respiration when succinate, pyruvate/malate or malate/glutamate was used as substrate. We suggest that high concentrations of acetate selectively impair fatty acid metabolism in heart issue. This in turn leads to decreases in ATP production and tissue ATP concentrations that ultimately result in impaired contractile function. As this occurs at relatively low concentrations of acetate, this finding may be relevant to other parenterally-administered acetate containing fluids.

Skeletal muscles subjected to ischemia and then reperfusion develop contractile dysfunction for reasons that are unclear. We found that rats pretreated with vinblastine 4 days before study had decreased numbers of blood neutrophils and increased gastrocnemius muscle function after ischemia (3h) and reperfusion (4 h) compared with untreated rats or rats treated 4 days before study with saline. By comparison, rats pretreated with vinblastine or saline 1 day before study had increased blood neutrophils and decreased gastrocnemius muscle contractile function after ischemia-reperfusion compared with untreated rats. In addition, numbers of neutrophils in gastrocnemius muscles paralleled numbers of blood neutrophils and correlated with gastrocnemius muscle edema and contractile function after ischemia and reperfusion. The results indicate that neutrophils accumulate and may play an important role in the genesis of skeletal muscle contractile dysfunction after ischemia-reperfusion.