Porcine alveolar macrophages (AM) metabolize leukotriene D4 (LTD4) to leukotriene E4 (LTE4). In the present study, the ability of a fluid-phase AM stimulus (A23187) and a phagocytic stimulus (opsonized zymosan) to augment LTD4 metabolism was examined. Both stimuli increased the release of superoxide (O-2) anions. However, whereas zymosan caused a consistent reduction in surface free energy, the effect of A23187 was variable. Similarly, zymosan induced release of the lysosomal enzymes N-acetyl-beta-D-glucosaminidase and arylsulphatase (mean net release, 14.9% and 12.0%, respectively), whereas release induced by A23187 was smaller (mean net release 1.42% and 1.31%, respectively) and of marginal statistical significance. Zymosan, but not A23187, caused a significant (P less than 0.005) augmentation of LTD4 inactivation: from 93 +/- 7 pM/10(7) cells (69 +/- 5% of added LTD4) at 60 min by control AM, to 117 +/- 3 pM/10(7) cells (88 +/- 2% of added LTD4) at 60 min by zymosan-treated AM. Zymosan also induced the release of LTD4 inactivating capacity (128 +/- 21 pM LTD4/10(7) AM/60 min) into the supernatant. Conversion of LTD4 to LTE4 by zymosan-treated AM and their supernatants was confirmed chromatographically. In addition, LTD4 inactivation by AM and their supernatants was inhibited by 10 mM L-cysteine. These data suggest that zymosan released a dipeptidase, possibly of lysosomal origin, which catalysed the conversion of LTD4 to LTE4.
Surface induced thrombosis remains an obstacle to extra-corpeal circulation and invasive investigation and therapy of the cardiovascular system. Although the molecular details of the blood-foreign surface interaction remain incompletely understood, from a thermodynamic viewpoint, thrombosis can only occur if thrombus formation lowers the free energy of the blood-surface system. We have recently reported a method of estimating surface free energies under physiological conditions from measurements of surface wetting by polar hydrophobic fluids. Here we report a correlation between interfacial energies and platelet retention on natural and artificial surfaces, and the effects on platelet retention of a synthetic coating developed in an attempt to mimic the thromboresistance of healthy endothelium. This coating has a lower surface energy than the artery and it appears to be equally thromboresistant.
1. The metabolism of rat renal cortex slices was inhibited by iodoacetate and anoxia, and swelling was prevented by the presence in the medium of 7·2 g polyethylene glycol 6000/100 ml. (referred to as PEG medium). 2. Slices were incubated for up to 12 hr in PEG medium, and in PEG media containing 440 m‐osmole/kg H 2 O of an electrolyte (LiCl, NaCl, KCl or RbCl), or a non‐electrolyte (glucose). 3. It was concluded that the slices in all media were at equilibrium with the medium after incubation for 8 hr. 4. Slices in the medium containing glucose reached the same equilibrium water content as those in the PEG medium, but slices in all the electrolyte media had significantly lower equilibrium water contents, although these did not differ significantly from each other. 5. It is suggested that the results demonstrate a non‐specific effect of electrolytes on the swelling of non‐metabolizing cells.
1. The spaces occupied by isotopically labelled inulin, polyethylene glycol, mol. wt. 4000 (PEG 4000), polyethylene glycol, mol. wt. 1000 (PEG 1000) and sucrose in metabolizing mammalian kidney and liver slices and in toad bladder epithelial cell preparations incubated in vitro have been examined.2. In slices of mammalian tissue, and in homogenized liver, it proved impossible to extract inulin completely from tissue which had been dried. However, inulin was recovered as completely from both dried and undried toad bladder epithelial cells scraped from hemibladders incubated in vitro.3. PEG 4000 occupied a space in all preparations similar to that from which inulin was extracted in dried tissue.4. PEG 1000 and sucrose entered cellular water in mammalian slices, but PEG 1000 occupied a similar space to inulin in toad bladder epithelial cell preparations.6. It is concluded that inulin enters cellular water in mammalian slices from which after drying of the slices it cannot be extracted. It thus rather fortuitously provides a measure of extracellular water under these conditions. In preparations of toad bladder epithelial cells inulin seems to be a satisfactory extracellular marker. PEG 4000, which did not appear to enter cellular water also allows a reasonable estimate of extracellular water. PEG 1000 is a suitable extracellular marker for toad bladder epithelial cell preparations but not for mammalian slices. Sucrose entered cellular water in both slices and toad bladder epithelial cells and is not a satisfactory extracellular marker in these tissues.
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