THE CORNEAL ENDOTHELIUM IN OCULAR SURFACE DISEASE AND GLAUCOMA: MECHANISMS OF DYSFUNCTION AND TREATMENT STRATEGIES.

To determine risk factors and the overall incidence of ocular surface disorders in a cohort of long-term glaucoma patients. Utilizing simple clinical tools, cross-sectional observational research were constructed to evaluate ocular surface problems and indicators. Using a four-grade scale, ten queries regarding symptoms and indications on the cornea's surface were used to create an OSD severity score. The patients were divided into three groups: A, B, and C, depending on the result. The variables that increase the incidence of surface sickness were identified using a multinomial logistic regression. Five hundred and twenty patients made up the total population. According to the multivariate analysis, the patient's age, the number of daily eyedrops, any previous changes in topical treatment for ocular intolerance, intraocular pressure, and degree of glaucoma were all connected with the severity of ocular surface illness. Ocular surface disorders are frequently developed by patients getting treatment for primary open-angle glaucoma or ocular hypotension. which are less prevalent and serious in geriatric patients because their use greater drugs and have greater advanced glaucoma.

UNDERSTANDING THE VITAL DETERMINANTS SHAPING LEARNERS' PHYSICAL ACTIVITYAND PSYCHOEMOTIONAL WELLBEING IN THE COVID-19 PERIOD.

The Corona Virus (COV-19) epidemic significantly affected the educational environment, requiring a quick transition to distance and blended learning methods. This extraordinary disruption had an incredible impact on pupil's levels of physical activity (PA), psycho-emotional health (PEH) and engagement with academic material. The research aims to examine the vital determinants that influenced various areas of learners' lives during CoV-19. The purpose of this 600-person study was to collect data on the subjects' overall health and PA levels for the CoV-19 pandemic. The SPSS application was used to process the questionnaire's collected data. The information given reveals the respondents' degree of PA throughout the quarantine. According to the breakdown, 15% indicated low levels of PA, 39% reported medium levels and 46% reported high levels. The data show that, despite the respondents' different levels of PA, little PA predominated for most of them. The limitations of distance learning throughout quarantine and the prevalent recommendation of leaving residence for necessary reasons were blamed for this tendency. There were fewer prospects for higher-intensity PA due to these circumstances.

Feasibility study of FDG PET/CT-derived primary tumour glycolysis as a prognostic indicator of survival in patients with non-small-cell lung cancer.

AIM: To assess the feasibility and prognostic value of measuring total lesion glycolysis of the primary tumour (TLG(primary)) using combined 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography/computed tomography (PET/CT) in patients with proven or suspected non-small-cell lung cancer (NSCLC) in the routine diagnostic setting. MATERIALS AND METHODS: At the All wales Research and Diagnostic Positron Emission Tomography Centre in Cardiff (PETIC), in the calendar year 2011, 288 consecutive patients were identified with a single pulmonary mass in whom NSCLC was confirmed or clinically diagnosed following multidisciplinary team review. In a retrospective analysis, for each patient the PET-derived volume of the primary tumour and SUVMEAN was calculated using adaptive thresholds of 40% and 50% of the SUVMAX of the primary tumour. The TLG(primary) (calculated by volume x SUVMEAN) was calculated at these two thresholds and was used to predict survival in a multivariate analysis with TNM (tumour, node, metastasis) stage, age, sex, and SUV(MAX). The primary endpoint was overall survival over a minimum follow-up of at least 7 months. RESULTS: In virtually every case, the primary tumour could be measured using the automated software with minimal use of manual adjustments. In multivariate analysis, TNM clinical stage, log(TLG(primary)) and sex were independent predictors of overall survival. CONCLUSION: Measurements of primary tumour total lesion glycolysis are simple to perform and provide additional prognostic information over and above that provided by TNM staging.

The permissive effects of glucose on receptor-operated potentiation of insulin secretion from mouse islets: a role for ERK1/2 activation and cytoskeletal remodelling.

AIMS/HYPOTHESIS: Glucose plays two distinct roles in regulating insulin secretion from beta cells--an initiatory role, and a permissive role enabling receptor-operated secretagogues to potentiate glucose-induced insulin secretion. The molecular mechanisms underlying the permissive effects of glucose on receptor-operated insulin secretion remain uncertain. We have investigated the role of extracellular signal-regulated kinase 1/2 (ERK1/2) activation and consequent cytoskeletal remodelling in this process. METHODS: Insulin release was measured from groups of isolated mouse islets using static incubation experiments and subsequent radioimmunoassay of samples. ERK1/2 activation was measured by western blotting of islet protein samples for both phosphorylated and total ERK1/2. Rhodamine-phalloidin staining was used to measure filamentous actin in dispersed primary beta cells. RESULTS: Inhibition of ERK1/2 blocked potentiation of glucose-induced insulin release by the receptor-operated secretagogues kisspeptin, A568, exendin-4 and JWH015, although the agonists alone had minimal effects on ERK1/2 activation, suggesting a permissive rather than causal role for ERK1/2 activation in receptor-operated insulin release. Following pharmacological activation of ERK1/2 all agonists caused a significant increase in insulin release from islets incubated with sub-stimulatory levels of glucose. ERK1/2 inhibition significantly reduced the glucose-dependent decreases in filamentous actin observed in primary beta cells, while pharmacological dissociation of actin filaments enabled all receptor-operated secretagogues tested to significantly stimulate insulin release from islets at a sub-stimulatory glucose concentration. CONCLUSIONS/INTERPRETATION: Glucose-induced ERK1/2 activation in beta cells mediates the permissive effects of stimulatory glucose concentrations on receptor-operated insulin secretagogues, at least in part through effects on actin depolymerisation and cytoskeletal remodelling.

Degradation of dipalmitoyl phosphatidylcholine by isolated rat granular pneumocytes and reutilization for surfactant synthesis.

We investigated metabolic utilization of exogenous (modelled after lung surfactant) phospholipids by granular pneumocytes in primary culture. Cells were incubated for 21, 65, and 140 min with [3H-methyl]dipalmitoylphosphatidylcholine (DPPC) containing liposomes prepared from synthetic lipids. Radioactivity in cellular phosphatidylcholine (PC) declined steadily to 50% of the total trypsin-resistant cell-associated radioactivity. The proportion of radioactivity increased with time in cytidine-5'-diphosphate-choline and phosphorylcholine, which suggested reutilization of choline for PC synthesis. Cells incubated with liposomes for 2 h revealed that of the total cell-associated radioactivity, 7% was in lamellar bodies and 10% in the microsomal fraction. The lipid-associated radioactivity was 24% in "soluble," 96% in lamellar bodies, and 92% in the microsomal fraction. Percent of total PC label recovered in disaturated PC of microsomal fractions decreased (slope = -5.27%/h) with time of incubation (r = 0.67). Incubation of cells with liposomes containing ([3H-methyl]choline-[14C]palmitoyl) DPPC led to altered isotope ratios in both lamellar bodies and microsomes. These observations indicate that granular pneumocytes degrade exogenous PC and resynthesize PC from degradation products.

An ethanol/ether soluble apoprotein from rat lung surfactant augments liposome uptake by isolated granular pneumocytes.

Ethanol/ether soluble apoproteins, comprising 17% of the total recovered surfactant-associated proteins, were isolated from rat lung surfactant and purified by silicic acid chromatography. The protein that eluted in 4:1 chloroform/methanol accounted for greater than 85% of protein in the ethanol/ether soluble fraction and was termed surfactant apoprotein Et (Apo Et). By sodium dodecyl sulfate polyacrylamide gel electrophoresis, this protein had an apparent molecular weight of approximately 10,500. Apo Et was evaluated for its effect on uptake of synthetic phospholipids in liposomal form by isolated granular pneumocytes (Type II alveolar epithelial cells) in primary culture. Liposomes were prepared to approximate the phospholipid composition of the alveolar surfactant, and uptake was measured by the accumulation of the radioactively labeled dipalmitoyl phosphatidyl choline fraction. The uptake of liposomal phosphatidylcholine by cells incubated for 2 h with Apo Et was increased by 61% over control. Most of the cell-associated phospholipid uptake was resistant to treatment with trypsin, suggesting an increased internalization of liposomal material in the presence of Apo Et. The effect of Apo Et on uptake was concentration and time dependent and was not associated with cell damage, phospholipase activity, or detergent properties of the protein. Apo Et had no significant effect on phosphatidylcholine uptake by granular pneumocytes maintained for 7 d in primary culture. Apo Et augmented the uptake of phospholipids by alveolar macrophages although total uptake by these cells was less than that observed with granular pneumocytes. Because Apo Et increases the rate of uptake of surfactant phospholipids by alveolar cells (granular pneumocytes and alveolar macrophages), this protein may represent a physiologically important regulator for clearance of lung surfactant phospholipids.

Dicyclohexylcarbodiimide and vanadate sensitive ATPase of lung lamellar bodies.

Lung surfactant is synthesized in lung epithelial type II cells and stored in the lamellar bodies prior to its secretion onto the alveolar surface. The lamellar bodies, like other secretory organelles, maintain an ATP-dependent pH gradient that is sensitive to inhibitors of H(+)-ATPase. This report shows that the ATPase activity of lamellar bodies is enriched in a fraction prepared from lamellar bodies that were disrupted after isolation. The apparent Vmax for this enzyme was 150 nmol ATP hydrolyzed per min per mg protein and apparent Km for ATP was approximately 50 microM. The enzyme activity was sensitive to N-ethylmaleimide (NEM), dicyclohexylcarbodiimide (DCCD) and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) (all inhibitors of vacuolar-type H(+)-ATPase) and vanadate (inhibitor of phosphoenzyme-type ATPase). Besides, the activity could also be inhibited with diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), and Ca2+. Two proteins (of approximately 45 kDa and 17 kDa) of this fraction showed acid-stable phosphorylation with ATP. The labeling of proteins with ATP (-gamma-32P) could be chased with unlabelled ATP, suggesting that phosphorylation and dephosphorylation of these proteins is associated with the ATPase activity. Our results on inhibition characteristics of the enzyme activity suggest that besides a vacuolar type H(+)-ATPase, the lamellar bodies also contain a phosphoenzyme type ATPase that is sensitive to inhibitors of vacuolar type H(+)-ATPase.

Stilbene disulfonic acids inhibit synexin-mediated membrane aggregation and fusion.

Stilbene disulfonic acids inhibit surfactant secretion from lung epithelial type II cells by an undefined mechanism, and inhibit CD4 mediated cell-cell fusion. We have previously shown that lung synexin promotes in vitro fusion of lamellar bodies and plasma membranes, an obligatory process for surfactant secretion. This study investigates the effect of stilbene disulfonic acids, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS), and 4-acetamido-4'-maleimidylstilbene-2,2'-disulfonic acid (AMDS), on synexin-mediated liposome aggregation and fusion. Structurally, these three stilbene compounds differ in the number of isothiocyano groups present (DIDS = 2, SITS = 1, and AMDS = 0). At 10 micrograms synexin/ml, DIDS and SITS inhibited synexin-mediated liposome aggregation with an EC50 of 3.5 microM and 148 microM, respectively. In comparison, AMDS was least inhibitory (EC50 > 1 mM). Thus, the inhibitory potency (DIDS > SITS > AMDS) was partly dependent upon the number of isothiocyano groups. The EC50 was also dependent on synexin concentration. Stilbene disulfonic acids were also inhibitory for arachidonic acid-enhanced synexin-mediated liposome fusion. The EC50 for DIDS and SITS for fusion were similar to that for liposome aggregation. Ca(2+)-induced synexin polymerization, measured by 90 degrees light scattering, was increased by DIDS, suggesting binding of stilbene disulfonic acids to synexin. The binding of DIDS to synexin was dependent on the molar ratio of synexin to DIDS. These results indicate that stilbene disulfonic acids interact directly with synexin to inhibit membrane aggregation and fusion. Our results suggest that such inhibition of synexin activity may contribute towards inhibition of surfactant secretion by DIDS, and support a physiological role for synexin in lung surfactant secretion.

Choline-phosphate cytidyltransferase activity and phosphatidylcholine synthesis in rat granular pneumocytes are increased with exogenous fatty acids.

We investigated the effect of exogenous fatty acids on phosphatidylcholine (PC) and disaturated phosphatidylcholine (DSPC) synthesis by rat granular pneumocytes in primary culture. Synthesis of PC and DSPC from [3H-methyl]choline, as evaluated by increasing specific activity (pmol choline incorporated/microgram phosphorus), was linear for 3 h. Exogenous palmitic, oleic, linoleic, or linolenic acid (100 microM each) increased the synthesis of PC by approx. 50% during incubation for 3 h. In contrast, synthesis of DSPC was increased only by palmitic acid. The increase in DSPC synthesis was approx. 150% after 3 h. Conversion of choline phosphate to PC was increased in the presence of palmitic or oleic acid as indicated by pulse-chase studies with [3H-methyl]choline in the intact cells. Cells incubated for 3 h with either oleic or palmitic acid showed increased choline-phosphate cytidyltransferase activity in the cells and the microsomal fraction. In addition, oleic acid increased the activity of this enzyme in the cytosolic fraction. The distribution of this enzyme in cytosolic and microsomal fraction was 24 and 76% in the cells incubated with palmitic acid and 32 and 68% in control cells. These results suggest that exogenous fatty acids stimulate the de novo pathway of PC synthesis in granular pneumocytes by increasing the microsomal choline-phosphate cytidyltransferase activity.

In vitro fusion of lung lamellar bodies and plasma membrane is augmented by lung synexin.

Lamellar bodies of lung epithelial type II cells undergo fusion with plasma membrane prior to exocytosis of surfactant into the alveolar lumen. Since synexin from adrenal glands promotes aggregation and fusion of chromaffin granules, we purified synexin-like proteins from bovine lung cytosolic fraction, and evaluated their effect on the fusion of isolated lamellar bodies and plasma membrane fractions. Synexin activity, which co-purified with an approx. 47 kDa protein (pI 6.8), was assessed by following calcium-dependent aggregation of liposomes prepared from a mixture of phosphatidylcholine:phosphatidylserine (PC:PS, 3:1, mol/mol). Lung synexin caused aggregation of liposomes approximating lung surfactant lipid-like composition, isolated lamellar bodies, or isolated plasma membrane fraction. Lung synexin promoted fusion only in the presence of calcium. It augmented fusion between lamellar bodies and plasma membranes, lamellar bodies and liposomes, or between two populations of liposomes. However, selectivity with regard to synexin-mediated fusion was observed as synexin did not promote fusion between plasma membrane and liposomes, or between liposomes of surfactant lipid-like composition and other liposomes. These observations support a role for lung synexin in membrane fusion between the plasma membrane and lamellar bodies during exocytosis of lung surfactant, and suggest that such fusion is dependent on composition of interacting membranes.

Glycerol kinase activity and glycerol metabolism of rat granular pneumocytes in primary culture.

Glycerol kinase activity and glycerol utilization by rat granular pneumocytes were determined in order to investigate the rate-limiting step for glycerol incorporation into lung lipids. Granular pneumocytes were isolated in primary culture following trypsinization of rat lungs. Glycerol kinase activity was 8.2 nmol/h per 10(6) cells. Incorporation of [1,3-14C]glycerol into total cell lipids was 0.29 nmol/h per 10(6) cells. In the presence of saturating glycerol concentration, production of 3H2O from [2-3H]glycerol was 13 times greater than incorporation of [14C]glycerol into lipids. Glycerol phosphate dehydrogenase activity in isolated cells was approximately 10 times glycerol kinase activity. In the presence of 5.6 mM glucose, glycerol incorporation into lipids was decreased 79% and detritiation of glycerol was decreased 34%. This effect of glucose was due to a 25% increase in cell glycerol 3-phosphate content, resulting in dilution of the precursor pool and possible inhibition of glycerol phosphorylation. These results indicate that the relatively limited incorporation of glycerol into surfactant phospholipids by lung epithelial cells reflects the relatively high rate of glycerol 3-phosphate oxidation.

Stimulation of the methylation pathway for phosphatidylcholine synthesis in rat lungs by choline deficiency.

The methylation of phosphatidylethanolamine (PE) to form phosphatidylcholine (PC) was investigated using the isolated rat lung perfused with radiolabeled ethanolamine. Lungs from choline-deficient rats showed increased incorporation of radiolabel into PC at 2 h of perfusion. Increased PC synthesis from PE was also observed with lungs from rats fed a lipotrophic (choline plus methionine deficient) diet when methionine was added to the lung perfusate. These results indicate increased activity of the methylation pathway for lung PC synthesis during choline deficiency.

Isolation of lamellar bodies from rat granular pneumocytes in primary culture.

A lamellar body fraction was isolated from rat alveolar granular pneumocytes in primary culture by upward flotation on a discontinuous sucrose gradient and compared with a similar fraction isolated from lung homogenates. Lamellar bodies from granular pneumocytes were free of detectable contamination with either succinate dehydrogenase or NADPH-cytochrome c reductase. There was an enrichment of acid phosphatase activity, which, based on distribution of enzyme activity on the gradient, did not appear to be a contamination from other fractions. The lamellar body fraction of granular pneumocytes yielded approx. 1 microgram protein/10(6) cells with a phospholipid-to-protein ratio (mg/mg) of 9.6 +/- 0.4 (n = 7). Composition with respect to total phospholipids was 71.0% phosphatidylcholine (disaturated phosphatidylcholine, 45.2%), 8.4% phosphatidylglycerol and 12.8% phosphatidylethanolamine. Palmitic acid comprised 66% of the fatty acids in phosphatidylcholine and 34% of those in phosphatidylglycerol. The lamellar body fraction from granular pneumocytes was similar to that from whole lung with respect to phospholipid-to-protein ratio and phospholipid composition and showed only minor differences in fatty acid composition. Ultrastructurally, lamellar bodies showed generally intact limiting membranes and lamellated structure. Lamellar bodies from granular pneumocytes showed occasional multinucleated whorls which were not seen in those isolated from lung homogenates. This study describes a method for preparing a homogeneous fraction of intact lamellar bodies from small amounts of material (6 X 10(7) granular pneumocytes). The yield on a per cell basis was higher when compared with a similar preparation from whole lung, although overall yield is small, due to loss of cells during the cell isolation procedure. This preparation may be useful to evaluate the role of lamellar bodies in the synthesis and secretion of lung surfactant by isolated granular pneumocytes.

Inhibition of Trimeresurus flavoviridis phospholipase A2 by lung surfactant protein A (SP-A).

A marked sequence homology has been noted between lung surfactant protein A (SP-A) and an inhibitor of phospholipase A2 (PLA2) isolated from the serum of Trimeresurus flavoviridis (Habu snake). This study evaluated the effect of SP-A on PLA2 activity from several sources. SP-A was isolated from bovine or rat lung surfactant by extraction with 1-butanol and octyl beta-D-glucopyranoside. The addition of SP-A produced a concentration-dependent inhibition of T. flavoviridis PLA2 that indicated non-competitive kinetics with Ki 5 micrograms/ml. Inhibition was reversed by heat inactivation, disulfide bond reduction or alkylation of SP-A, or by the presence of anti-SP-A antibody. Treatment of SP-A with endoglycosidase F or the presence of variation monosaccharides or lectins did not alter SP-A inhibition. Binding of PLA2 to SP-A was shown by ultrafiltration and was abolished by SP-A alkylation or the presence of SDS. The SP-A/PLA2 complex recovered from the ultrafilter had essentially no enzymatic activity, but activity was restored by treatment with mercaptoethanol. SP-A had no effect on activity of PLA2 from Naja naja, Crotalus atrox, or bovine pancreas. These results indicate that surfactant protein A selectively inhibits Trimeresurus phospholipase A2 activity and suggest that binding to the enzyme is the mechanism for inhibition.

Inhibition of phosphatidylcholine secretion by stilbene disulfonates in alveolar type II cells.

Various agents stimulate the secretion of lung surfactant from alveolar type II cells by increasing intracellular Ca2+, cyclic adenosine-3':5'-monophosphate (cAMP), or diacylglycerol. A few agents, including the purified surfactant protein A, are known to inhibit the secretion by an unknown mechanism. In the present study, we demonstrated that stilbene disulfonic acids, 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) and 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS), are potent but reversible inhibitors of lung surfactant secretion. The inhibition was concentration dependent, and the EC50 was 5 microM for DIDS and 50 microM for SITS. The inhibition was not specific to agonists for any one type of receptor, and was also observed for secretion stimulated by 8-bromo-cAMP, or tetradecanoyl phorbol acetate, suggesting that the site of inhibition was distal to the generation of intracellular second messengers. This was also supported by the failure of DIDS to block the stimulus-mediated increase in diacylglycerol content of type II cells. Further, DIDS and SITS were also inhibitory for basal secretion. Based on the reversibility of inhibition and the fact that inhibition was observed with both basal and stimulated secretion, we suggest that stilbene disulfonic acids affect a component of the exocytosis process that occurs at or near the plasma membrane.

Activation of protein kinase C by 1,4-dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)-phenyl]-3-py rid ine carboxylic acid methyl ester (Bay K 8644), a calcium channel agonist, in alveolar type II cells.

A role for calcium channels in the regulation of surfactant secretion is suggested by the observation that endothelin-1-stimulated surfactant secretion is inhibited by calcium channel blockers. 1,4-Dihydro-2,6-dimethyl-5-nitro-4-[2-(trifluoromethyl)-phenyl]-3-pyridi ne carboxylic acid methyl ester (Bay K 8644), a dihydropyridine derivative, stimulates voltage-dependent and non-voltage-dependent calcium channels in a number of cell types. This study demonstrates that Bay K 8644 increased phosphatidylcholine (PC) secretion in isolated lung epithelial type II cells in a time- and concentration-dependent manner with an EC50 of 100 +/- 8 nM (mean +/- SEM, N = 6). The secretagogue effect of Bay K 8644 was independently decreased in the absence of external calcium, or in the presence of nifedipine, a calcium channel antagonist, or inhibitors of protein kinase C (PKC). Bay K 8644 increased intracellular calcium from 130 +/- 8 to 230 +/- 14 nM (N = 6, P < 0.05), an effect that was blocked by nifedipine. Bay K 8644 also increased the membrane-associated PKC activity in a concentration-dependent manner. In the membranes from Bay K 8644-stimulated cells, the increase in calcium-dependent PKC was greater than that in the calcium-independent PKC, suggesting preferential translocation of calcium-dependent PKC to the membranes. We suggest that both elevated calcium and activation of PKC are required for calcium agonist Bay K 8644-induced surfactant secretion in type II cells.

Differential response of lung and liver of juvenile rats to choline deficiency.

The effect of choline deficiency on the lung lipids of actively growing male Sprague-Dawley rats was investigated using a washed soy protein diet deficient in choline and methionine (lipotrophic). The livers from deficient animals had a significantly increased total lipid content and decreased phosphatidylcholine (PC) content and PC-to-phosphatidylethanolamine ratio (P less than 0.01). Although lung free choline levels were decreased 40% compared with controls (P less than 0.05), the PC content of the whole lung homogenate was unchanged. However, disaturated phosphatidylcholine from animals receiving the lipotrophic diet was significantly increased in the lavage and proportionally decreased in the lavaged lung tissue compared with controls (P less than 0.01). This study indicates that, despite decreased lung choline levels as a result of ingesting a lipotrophic diet, and unlike the liver, lung PC content is maintained at normal values. Although the lung total PC levels are maintained, there is a change in the partition of this lipid pool between the tissue and the alveolar space.

Degradation and reutilization of alveolar phosphatidylcholine by rat lungs.

We have shown previously that phospholipids instilled through the trachea are removed from the air spaces in isolated rat lungs by a process that is stimulated by beta-adrenergic agonists. In this study, we evaluated the fate of radiolabeled lipid vesicles [50% [3H]dipalmitoyl phosphatidylcholine (DPPC), 25% phosphatidylcholine (PC), 15% cholesterol, and 10% phosphatidylglycerol (PG)]. Vesicles were instilled through the trachea of anesthetized rats, and the lungs removed for perfusion. The percent of instilled 3H that could not be removed from lungs by extensive lung lavage increased progressively; at 3 h this fraction was 25.8 +/- 0.63% (mean +/- SE; n = 8). The percent of dpm in the lung homogenate accounted for by PC decreased progressively while dpm in lyso-PC, unsaturated PC, and aqueous soluble metabolites [choline, choline phosphate, glycerophosphorycholine, and cytidine 5'-diphosphate (CDP) choline (CDP-choline) increased. The dpm in microsomal and lamellar body fractions isolated from lung homogenates also increased progressively with time of perfusion. The presence of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) significantly stimulated both uptake of DPPC and the appearance of radioactivity in metabolites and subcellular organelles. This effect of 8-BrcAMP was not due to stimulation of phospholipase A activity. These results indicate that exogenous phospholipids instilled into the air spaces of rat lungs are internalized and degraded by a process that is stimulated by cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)