Oleic acid dose-related edema in isolated canine lung perfused at constant pressure

Fatty acid embolism of the lung results in pulmonary edema. Isolated lung lobes ventilated and blood perfused at constant pressure were treated with 1 (n = 6) or 45 microliter/kg body wt (n = 6 oleic acid or saline (n = 7). Lobe weight increase linearly over 1-3 h following oleic with regression slopes indicating a more rapid rate of weight gain at the higher oleic acid dosage. Total lobe weight gain was greater in the 45 than in the 1 microliter/kg group (0.60 +/- 0.10 vs. 0.31 +/- 0.07 g/g initial lobe wt) and greater in the acid-treated lobes than in the controls (0.13 +/- 0.05 g/g initial lobe wt). Pulmonary vascular resistance increased 79% after 45 microliter/kg oleic acid but appeared unchanged following 1 microliter/kg oleic acid or saline. The decrease in arterial O2 partial pressure was greater in the 45 microliter/kg group than in the controls, 47 vs 22 Torr. High vascular pressures and increased flow velocities in patent vessels are not essential for oleic acid-associated edema, since weight increased at constant pressure perfusion. Weight gain related to oleic acid dosage suggests that oleic acid increases permeability by affecting the vascular endothelium either directly or through biochemical intermediates endogenous to the lung or blood.     

The metabolism of the isolated perfused canine liver

An isolated liver perfusion was used for metabolic interrelation studies in our laboratory. The liver slices, after a 2-hr perfusion period in various pretreated groups, were also studied for carbohydrate metabolism. It was found that aerobic and anaerobic metabolism of liver slices treated with deoxycorticosterone acetate, testosterone, and partial ligation of the thoracic inferior vena cava, were the same as in normal livers. We also observed depression of the glycolytic pathway for utilizing exogenous fructose in the group pretreated with carbon tetrachloride and common bile duct ligation. An increase in oxygen ocnsumption in common bile duct-pretreated animals was also observed. Such studies suggest that hepatic metabolic performance in vitro or after perfusion cannot, therefore, provide infallible information on the prior presence of important host drug treatments in hepatic disease states. Such features may complicate donor considerations in hepatic transplantation patients.     

Surfactant cholesterol metabolism of the isolated perfused rat lung

The cuticle (0.15 to 0.5 microns thick) of the microscopic free-living nematode Panagrellus silusiae was isolated intact by incubating worms with 1% sodium dodecyl sulfate at 37 degrees C overnight. After shearing and further treatment with detergent, electron microscopy revealed that the cuticular pieces were free of contaminating material and retained their characteristic in situ ultrastructure. From amino acid determinations, the cuticle is collagen-like with high levels of glycine (approximately equal to 31 residue %), proline (approximately equal to 20 residue %) and alanine (approximately equal to 21 residue %) although the hydroxyproline (2.6 residue %) content is low. Half-cystine (approximately equal to 1 residue %) is present in purified cuticles. Treatment with 8 M guanidine hydrochloride-2% beta-mercaptoethanol can solubilize more than 85% of the cuticular preparation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the solubilized cuticles from juvenile, adult and old dead worms revealed, at least, 18 discrete components. Estimated molecular weights ranged from about 26 000 (peak 1) to 250 000 (peak 18).     

Disappearance of enkephalins in the isolated perfused rat lung

Enkephalin disappearance during a single passage through the isolated, Krebs'-perfused rat lung was examined by superfusion bioassay. The rat colon was used to quantitate enkephalin disappearance since it proved to be sensitive to physiologic concentrations (10^?11M) of met⁵-enkephalin or an analog D-ala²-D-leu⁵-enkephalin. The rat stomach strip was used to assess the release of prostaglandins from the pulmonary vasculature. The rat lung rapidly degraded the enkephalins but released no prostaglandins in the dose-range of 0.1 – 50 ng. Captopril at doses which blocked conversion of angiotensin I to II inhibited the degradation of enkephalins across the lung.     

Glutathione conjugation by isolated lung cells and the isolated, perfused lung. Effect of extracellular glutathione

Cells isolated from rat lung by protease digestion were found to catalyze the reduced glutathione (GSH) conjugation of 1-chloro-2,4-dinitrobenzene. The rate of conjugation was stimulated severalfold in the presence of GSH, indicating uptake and utilization of extracellular GSH by the lung cells. The stimulation was dependent on the GSH concentration and not due to a spontaneous nonenzymatic reaction or to extracellular GSH-transferase activity. Conjugation of 1-chloro-2,4-dinitrobenzene was also measured using isolated perfused rat lung. The conjugation, which was linear for a longer time than with the isolated cells, was also stimulated in the presence of GSH in the perfusion medium. The results indicate the ability of rat lung to utilize extracellular GSH.     

Prostaglandin removal and metabolism by isolated perfused rat lung

We have investigated the mechanism(s) involved in the removal of prostaglandins (PG) from the pulmonary circulation by the lung. Unidirectional fluxes of PG from the circulation into the lung are measured in an isolated perfused rat lung preparation. Evidence is presented which suggests that a transport system for PG exists in lung tissue. This transport system is responsible for the removal of some PG from the circulation by the lung. PGE₁ and PGF_2α are substrates for this system, whereas PGB₁, PGA₁, and 15-keto-PGF_2α are not. Since PGA₁ is a substrate for the intracellular PG dehydrogenase, the selectivity of the lung's metabolism system for circulating PG is probably due to the selectivity of the transport system for PG. It is shown that the percentage of the pulmonary arterial concentration (C_A) of PGE₁ or PGF_2α that is metabolized on passage through the pulmonary circulation decreases rapidly as C_A increases. When the lungs were perfused with PGE₁ (PGF_2α), the metabolites detected in the venous effluent were 15-keto-PGE₁ (PGF_2α) and 15-keto-13,14-dihydro-PGE₁ (PGF_2α). The time course pattern of the appearance of metabolites in the venous effluent after the initiation of a constant C_A, and the relative concentrations of the metabolites in the venous effluent, were examined as a function of C_A.     

Metabolism of environmental pollutants by the isolated perfused lung.

An isolated perfused rabbit lung system was developed for the study of pulmonary metabolism of foreign compounds. The main features of the system include the use of autologous whole blood, constant pressure perfusion, subatmospheric ventilation, and measurement of a variety of physiological and biochemical parameters. Pulmonary metabolism of benzo(a)pyrene has been investigated with this system. In addition to the 3-hydroxy metabolite, three dihydrodiols and an unidentified polar metabolite were also found. The polar metabolite accounted for approximately 50% of all metabolites found in the five compartments of the perfusion system. Pretreatment with 3-methylcholanthrene increased total metabolism of benzo(a)pyrene and shifted the pattern of metabolites. The perfusion system for the rabbit has been extensively modified for use with rats and guinea pigs. These smaller animals are currently being used to investigate pulmonary metabolism of trichloroethylene.     

N-oxidation of imipramine by isolated perfused rat and rabbit lung

Pulmonary uptake and metabolism of imipramine (IMP) was investigated in isolated perfused rat (IPrL) and rabbit (IPRL) lung preparations. Perfusate containing ¹⁴C-IMP (1.2 μmole/g lung) was recirculated through the pulmonary artery in artificially ventilated lungs. The radioactivity in the perfusate declined rapidly and about 80% of the dose was taken up by the lungs within 10 minutes in both IPrL and IPRL preparations. A steady-state was apparently reached thereafter in the IPRL, while a portion of the radiolabel effluxed into the perfusate of the IPrLs, thus reducing the net lung content to 54% of added IMP by 60 minutes. After 60 minutes perfusion, metabolites of IMP accounted for the major radioactivity (80%) in the perfusate, while the lung contained mainly (83%) the unchanged parent compound. The principal metabolite was identified as IMP-N-oxide (IMP-NO) which was found in the perfusate after 5 minutes of perfusion. Only 3% of the added IMP was metabolized by IPRL in 60 minutes. SKF-525A, an inhibitor of cytochrome P-450-mediated monooxygenase system, did not inhibit but enhanced the metabolism of IMP by IPrL to IMP-NO. IMP was principally metabolized to IMP-NO by incubations of 9,000 g supernatant fractions of rat lungs to a significantly higher extent than similar rabbit lung preparations. Including SKF-525A significantly accelerated the metabolism of IMP to IMP-NO in accordance with the perfusion experiments. These results suggest that in contradiction to publishedd reports, IMP is appreciably metabolized by the rat lung $\text{via}$ N-oxidation by non-cytochrome P-450 pathway and the metabolite formed in the lung is released into the circulation indicating its low affinity for the lung tissue.     

Use of the isolated perfused rat lung in studies on lung lipid metabolism

A procedure for the use of the isolated perfused rat lung in studies on metabolic regulation has been developed. The procedure, reasonably uncomplicated, yet physiological, maintains the lung so that edema is not observed. The phospholipid content remains normal, and incorporation of [1-(14)C]-palmitate, [2-(14)C]acetate, and [U-(14)C]glucose is linear with time for a minimum of 2 hr. The incorporation of [1-(14)C]-palmitate and [2-(14)C]acetate into the total lung phospholipid fraction and into the phosphatidylcholine and phospatidylethanolamine fractions has been studied. Increasing the concentration of palmitate in the medium from 0.14 to 0.51 mm increased by 60% the incorporation of [1-(14)C]palmitate into the total lung phospholipid fraction at 2 hr. When the palmitate concentration of the medium was 0.14 mm, addition of 0.11 and 0.79 mm oleate to the medium decreased [1-(14)C]palmitate incorporation into the total lung phospholipid fraction at 2 hr by 37 and 49%, respectively. The results suggest that the incorporation of exogenous fatty acids, present in the medium perfusing the lung, into lung phospholipids may depend upon the fatty acid composition of the medium. Known specific acyltransferase activities may be responsible for the ordered incorporation of available fatty acids into lung phospholipids.     

Jejunal factor stimulating insulin release in the isolated perfused canine pancreas and jejunum.

In the present study using an isolated perfused preparation of canine jejunum and pancreas, an insulin-releasing factor was found in the venous effluent of the jejunum. Insulin secretion by the pancreas rose twofold after 10% glucose was infused in the lumen of the jejunum and remained at a high level even after the stimulus was discontinued. No modification of the exocrine pancreatic secretion occurred during the insulin release, and therefore it seems unlikely that gastrin, secretin or cholecystokinin-pancreozymin were released by the jejunal mucosa. In control experiments the values of hyperglycaemia observed previously and intraluminal hyperosmolarity were tested: at these levels, they did not affect insulin secretion. The nature of this intestinal insulin-releasing factor remains unknown however, but may be identifiable when intestinal hormones in blood can be assayed reliably.