Effect of different non-steroidal anti-inflammatory drugs, aspirin, nimesulide and celecoxib on the disaccharide hydrolases and histoarchitecture of the rat intestinal brush border membrane

Non-steroidal anti-inflammatory drugs (NSAIDs) are known to cause gastrointestinal damage. New anti-inflammatory drugs have been developed in an attempt to improve their gastrointestinal side effect profile which however failed to do so. Therefore, the objective of the present study was to compare the effect of three different NSAIDs, aspirin, nimesulide and celecoxib on the intestinal brush border membrane (BBM) marker enzymes and correlate these alterations to the histoarchitecture of the intestine using electron microscopic study. Female Wistar rats were divided into four different groups viz: Group I (Control), Group II (aspirin treated), Group III (nimesulide treated) and Group IV (celecoxib treated). The Group II, III and IV received the corresponding drugs dissolved in water orally at a dose of 40 mg/kg body weight, while the control received the vehicle only. After 28 days, all the treatment groups demonstrated significant alterations in the activities of intestinal disaccharide hydrolases and alkaline phosphatase in both the crude homogenates and BBM preparations as well. The histopathological observations also showed considerable changes in the intestinal mucosa. It was suggested that NSAIDs like aspirin, nimesulide and celecoxib pose intestinal side effects due to initial changes in the enzymatic composition of the intestinal apical membranes. It was further concluded that newly discovered NSAIDs such as celecoxib has better safety profiles but studies are still required to comment decisively on the suitability of various NSAIDs depending upon their cyclooxygenase enzyme specificity.

Effect of nonsteroidal anti-inflammatory drugs and the procarcinogen 1,2-dimethylhydrazine on the antioxidant defense system

The present study was designed to evaluate the effects of three nonsteroidal anti-inflammatory drugs (NSAIDs) with varying cycloxygenase selectivities on the small intestinal antioxidant enzyme status and surface characteristics during 1,2-dimethylhydrazine (DMH) administration. Male Sprague-Dawley rats were divided into five different groups: Group 1 (control, vehicle treated); group 2 (DMH treated, 30 mg/kg body weight/week, subcutaneously); group 3 (DMH + aspirin 60 mg/kg body weight); group 4 (DMH + celecoxib 6 mg/kg body weight); group 5 (DMH + etoricoxib 0.64 mg/kg body weight). Postmitochondrial fraction were isolated from the intestinal segments and different oxidative parameters and other parameters studied, such as the lipid peroxides, reduced and total glutathione, superoxide dismutase, catalase, glutathione reductase, glutathione S-transferase, nitric oxide, citrulline, and nucleic acids. At the end of 6 weeks of treatment, the results indicated a significant alteration in the antioxidative defense status of the intestine in the presence of the procarcinogen DMH, which was restored with the administration of NSAIDs. The study, therefore, suggests a possible mechanism for the chemopreventive effects of NSAIDs against the experimental intestinal cancer in rats.

Oxidative effects of Na+--specific ionophore monensin on the rat epididymis

The carboxylic antibiotic ionophore monensin is well-known for the Na+/H+ exchanger activity across the biological membranes. The current study has been designed to investigate the effect of monensin on spermatozoal concentration, motility, and oxidative stress-related parameters in the rat epididymis. Monensin was administered orally at a dose of 3.5 mg/kg body weight daily for 70 days, a duration that coincides with the completion of the spermatogenic cycle. At the end of the respective treatment, the epididymis was isolated into three separate regions--the capitum, corpus, and the cauda--successively away from the head of the testis. Marked changes were noted in the body weight, organ (epididymis) weight, sperm concentration and motility, as well as the morphologic observations of the sperm and the histologic architecture of the epididymal epithelium. Significant alterations were also recorded in the oxidative stress parameters such as the lipid peroxidation product, malonyldialdehyde, and the activity of superoxide dismutase, glutathione sulfotransferase, glutathione reductase, and catalase. The nonenzymatic thiol content such as the total, oxidized, and reduced glutathione showed significant changes and the tissue phosphatases such as alkaline and acid phosphatase were increased, indicative of the interference of the drug in lysosomal and Golgi membrane complex. The findings of the current study indicate interactions during the spermatozoal maturational process in the epididymis, and a significant potential use of monensin in male contraception may be suggested.

Effect of monensin on the enzymes of oxidative stress, thiamine pyrophosphatase and DNA integrity in rat testicular cells in vitro

Monensin, a sodium specific ionophore was evaluated for its in vitro effects on rat testis by studying changes at biochemical parameters as well as at the DNA level. It was observed that monensin produced marked alterations in the activities of various enzymes associated with the testicular functions. The significant inhibition of different enzymes of oxidative defense system points toward the generation of reactive oxygen species (ROS) by monensin treatment. The significant depletion of reduced glutathione and elevation in the level of lipid peroxidation further support the above findings. The significant inhibition of the activities of lactate dehydrogenase and adenosine triphosphatase shows the interference of monensin with the normal energy supply in spermatogenesis. Moreover, the significant increase in the activities of acid phosphatase and thiamine pyrophosphatase demonstrates the interference of monensin with the Golgi-lysosomal complex of the rat testis. Induced DNA fragmentation indicates towards the impact of monensin on the DNA integrity and apoptosis. Further studies are needed to understand the important molecular mechanisms responsible for these effects.

Modulations in the intestinal disaccharide hydrolases and membrane dynamics: effect of non-steroidal anti-inflammatory drugs aspirin and nimesulide

The present study was designed to evaluate the influence of two commonly prescribed non-steroidal anti-inflammatory drugs (NSAIDs), aspirin and nimesulide on the biochemical composition and membrane dynamics of rat intestine. Female Wistar rats were divided into three different groups viz: Group I (Control), Group II (aspirin-treated, 50 mg/kg body weight) and Group III (nimesulide-treated, 10 mg/kg body weight). After 28 days, biochemical estimations in both drug treated groups showed an increase in sucrase, lactase, maltase and alkaline phosphatase as compared to the control. Alterations in the intestinal membrane dynamics by fluidity studies and Fourier Transform Infra Red (FTIR) spectroscopy also showed considerable changes. The alterations in the histoarchitecture of the intestine were also seen, which correlated well with the changes in structure and composition of the intestine. The use of NSAIDs like aspirin and nimesulide may cause the gastrointestinal side effects due to initial changes in the enzyme activities and membrane dynamics.

Characteristics of glucose transport across the microvillous membranes of human term placenta

Transport characteristics of D-glucose were studied in the microvillous vesicles isolated from the human term placenta. Transport occurred by selective and rapid facilitated diffusion system which was inhibitable by phloretin and HgCl2. The transport was dependent on a transmembrane. Na+-gradient indicating a "secondary active transport" system operating. The transport influx was saturable and the kinetic analysis based on Hanes-Woolf plot produced a kt and Jmax value of 1.2 mM and 34 nmoles.mgprotein(-1).min(-1), respectively. The efflux of D-glucose from the membrane vesicles in a pre-equilibrated assay conditions showed a distinct biphasic pattern differing significantly in the half time efflux. The t1/2 of the fast and slow components was found to be 15 sec and 660 sec, respectively. The transport showed distinct sensitivity to temperature and the Ea values both below and above the transition temperature of 37 degrees C, as calculated from the Arrhenius plot were found to be 7600 and 5472 kCal.mol(-1), respectively. Inhibition studies with a number of sugars for hexose transport pathway showed that the glucose epimers, phosphorylated sugars, and even the disaccharides and the pentose sugars competed effectively with D-glucose. The influx was also inhibited by a number of steroids such as progesterone, 17alpha-hydroxyprogesterone, testosterone and estrogen. Insulin was found to increase glucose transport in a dose- dependent fashion at a concentration of 0.2-1 unit.ml(-1). Ouabain, dinitrophenol and nicotine strongly inhibited D-glucose uptake in the membrane vesicles.

Role of phospholipid transfer protein in rabbit lung development

A 36-kDa phospholipid transfer protein (PLT-P(R)), which preferentially transfers phosphatidyl choline (PC) compared to phosphatidyl inositol (PI), was purified 827-fold from rabbit lung homogenate. Incorporation of cholesterol in unilamellar vesicles reduced the PC transfer activity of PLTP(R). Dipalmitoyl phosphatidyl choline uptake by alveolar type II cells was increased in the presence of the protein, and further enhanced in the presence of surfactant liposomes. However, a decrease in uptake was noted with cholesterol in host membranes. Incorporation of PI into host membranes had a low stimulatory effect on the process. All these effects were more pronounced in adult type II cells compared to premature, term and 3-day-old pups.

Effect of antioxidant vitamin E as a protective factor in experimental atherosclerosis in rhesus monkeys

Atherosclerosis has been known for many years, yet its etiology remains unknown. Hypercholesterolemia is a major risk factor for atherosclerosis. The mechanism by which it triggers endothelial injury is not known. Since the role of the antioxidant vitamin E on experimental atherosclerosis is inconsistent, the present study was undertaken to evaluate platelet lipid peroxidation and the role of vitamin E (alpha-tocopherol) as protective factor in atherosclerosis in rhesus monkeys. A significant decrease in serum cholesterol and serum triglyceride levels was found in the group of animals which were reverted to stock diet along with vitamin E injections after 9 months of atherogenic diet feeding. Decreases in malonyldialdehyde levels and antioxidant enzyme activities were less significant in animals continued on an atherogenic diet feeding along with vitamin E as compared with animals fed a stock diet with vitamin E supplementation. The overall observations in this study suggest that antioxidant status and lipid peroxidation could be partly restored with vitamin E supplementation in experimental atherosclerosis. Damage to endothelial cells destroys their antithrombotic status and leads to fatal thrombosis. alpha-Tocopherol offers the best hope, but the question is how much of it should be administered for the prevention of atherosclerosis.

The role of oxidized HDL in monocyte/macrophage functions in the pathogenesis of atherosclerosis in Rhesus monkeys

The effect of oxidative modification of high-density lipoprotein (HDL) was assessed by incubation of normal HDL (obtained from Rhesus monkeys fed a stock diet) with 5 microM CuSO4 at 37 degrees C for 12 h/24 h. The physicochemical properties of oxidized-HDL (Ox-HDL) were found to be affected in terms of lipid peroxidation, as observed by the increased level of thiobarbituric acid reactive substances (nmol MDA/mg HDL protein). The biological properties of HDL were altered, since a decrease in the efflux of free cholesterol into the medium was found in the presence of Ox-HDL24h compared with normal HDL (N-HDL). The binding, uptake and degradation of 125I-LDL by macrophages increased in the presence of Ox-HDL24h. The activity of antioxidant enzymes (superoxide dismutase, catalase and glutathione-peroxidase) was reduced in monocytes in the presence of Ox-HDL. However, in the presence of N-HDL, the levels of antioxidant enzymes were maintained at a higher level than in the control (in the absence of HDL) monocytes. Furthermore, the number of monocytes adhered to aortic endothelium were found to be increased in the presence of Ox-HDL. These findings suggest that HDL is susceptible to oxidative modification. Since the parameters selected in the present study are involved in the pathogenesis of atherosclerosis, it can be postulated that the in vivo protection of HDL in atherosclerosis can be reversed in the circumstances in which HDL undergoes oxidative modification like low-density lipoprotein (LDL).

Effect of lung surfactant liposomes on the rabbit fetal lung type II cell antioxidant enzymes following prenatal dexamethasone treatment

Prematurely born infants are at a high risk of developing neonatal respiratory distress syndrome (RDS), and it is believed that besides an insufficient surfactant (SF) system the initial breathing of O2-enriched air may in some way be responsible for this syndrome. Hyperventilation is a dominant stimulator for SF secretion but it may lead to oxidant-mediated cellular injury to type II cells. Since type II cells are the sole source of SF synthesis, the effect of ventilation support on these cells becomes important. In the present study, the changes in the antioxidant enzymes (AOEs) such as superoxide dismutase (SOD), catalase and glutathione peroxidase (GPX) in the type II cells of fetal rabbit lungs resulting from exogenous SF liposomes and steroid intervention have been investigated. The specific activities of the AOEs were found to be higher in the presence of SF liposomes in prematurely born pups whose mothers were not steroid treated (control), while such an increase was more pronounced in dexamethasone-treated groups. The results indicate that the exogenous surfactant and steroid intervention may favourably alter the AOE defences in the type II cells of fetal rabbits.

Near ultraviolet radiation induced changes in goat lens

The possibility that the ultraviolet radiation from sunlight and other ambient sources as a major causative factor for the onset of cataract processes and photolytic changes of the eye lens constituents was studied. Normal goat lenses exposed in vitro to near UV radiation in the region of 315-400 nm (UV-A) revealed distinct morphological changes in the ultrastructure, increase in the inorganic elements; C, H, N, and a sharp shift in the intrinsic fluorescence spectra. UV exposure resulted in an alteration in the lambda max of the excitation spectra, a red shift in the emission absorption maxima and also an increase in the absolute fluorescence intensity. Scanning electron microscopic study showed a significant increase in the interfibrillar distances of the lens structural proteins. It is argued that the UV light induced covalent modifications of the lens proteins and their aggregations might have occurred due to the generation of photolytic products which then lead to oxidative damages.

Isolation of type II epithelial cells from rabbit fetal lungs by adherence on an IgG-coated surface

The lung is comprised of about 40 different cell types, of which only 15% are type II cells. These are the major, if not the sole, source of synthesis and secretion of lung surfactant. To date a large number of methods have been described for the isolation of pure populations of type II cells using a wide variety of techniques, but most of these have employed differential centrifugation methods and have used adult rodents. The present study reports the isolation of type II cells from fetal rabbit lungs by the immunoglobin G plating method. Pure populations of fetal type II cells in high yield and with good viability were obtained by the procedure for the first time from rabbit fetal tissue.

Isolation and characterization of the basal cell membranes of the human term placenta

A relatively simple and rapid method is described for the isolation of basal cell membranes (BCM) from the human placenta at term which showed considerable improvement in the yield, purity and membrane characteristics as compared to the earlier described methods. The method is based on thorough washings of the syncytium in balanced salt solution, selective grinding, hypotonic lysis, sonication, incubation with EDTA and then more conventional differential centrifugation and ultracentrifugation. The isolated material showed smooth surfaced vesicular structure of various sizes as revealed by both positive and negative staining and transmission electron microscopic analysis. The membrane was highly enriched in Na+/K+, Ca2+ and Mg2+ dependent ATPase activities while the cross contamination with brush border surfaces was low as revealed by the marker enzyme assays specific for the brush border membrane (BBM) such as the disaccharide hydrolases, aminopeptidase and alkaline phosphatase. The membrane showed a relatively low lipid/protein ratio and the lipid composition represented by a variety of phospholipids (phosphatidyl choline, phosphatidyl ethanolamine, sphingomyelin, phosphatidyl inositol and phosphatidyl serine), neutral lipids (cholesterol, triacyl glycerol, free fatty acids) and glycosphingolipids (ganglioside, cerebroside and sulfatide). It also contained plasmalogens. On SDS-PAGE analysis and Coomassie blue staining reaction, the isolated membrane showed 14 major bands with as many minor ones with a molecular weight ranging between 30-110 kDa.

Ca(2+)-transport across brush border and basal surfaces of human term [correction of terms] placenta

Brush border microvillous (BBM) and basal cell membranes (BCM) were isolated from syncytiotrophoblast of human term placenta by homogenization, sonication, prolonged stirring and differential centrifugation. Uptake of 45Ca(2+)-CaCl2 in membrane vesicles in morpholino propane sulphonic acid (MOPS) buffer was studied up to 60 min. Maximum uptake of the radioisotope was recorded at 10 and 15 min of incubation of the BBM and BCM, respectively. Radioisotopic uptake was also dependent on the Ca(2+)-concentration, linear up to 3 mu mole and then assuming hyperbolic substrate saturation kinetics. The Lineweaver-Burk transformation of the data gave Kt value for BBM and BCM, 0.85 and 1.08 microM, respectively while the Vmax of uptake (Jmax) in the same were 105.26 and 188.68 pmole Ca2+/microgram protein/20 min. Ca(2+)-Uptake in placental BBM and BCM vesicles was inhibited by two Ca(2+)-channel blockers, nifedipine and verapamil to as much as 50% while Ca(2+)-ionophore A23187 enhanced the uptake process significantly.

Transport of glycine in the brush border and basal cell membrane vesicles of the human term placenta

Active glycine transport was demonstrated in microvillous (maternal-facing, BBM) and basal (fetal-facing, BCM) plasma membranes of the human term placental syncytiotrophoblast. The kinetic studies showed that the amino acid had a distinct overshoot at 1 min in BBM and 3 min in BCM vesicles while a steady state rate was achieved in approx 5 min in both the vesicles. Glycine transport is highly ion-specific and its dependency on Na+ can not be satisfied by replacing with other monovalent cation. Cl- is also implicated in the generation of the electrochemical gradient and replacement of Cl- with SO4(2-) anions failed to stimulate the transport process. The transport process was saturable with external glycine which exhibited rectangular hyperbolic kinetics typical of a mediated movement. The calculated kt and Jmax from the linear transformation of the data were 6.67 & 4 mM and 294 & 263 nmoles glycine. mg protein-1.min-1 in the BBM and BCM vesicles, respectively. The glycine transport was inhibited by a number of other amino acids which are known to be transported through the A and ASC systems. The glycine transport system may be dependent on multiple pathways such as the A, ASC or Gly which is a variant of pathway A. Glycine transport was inhibited by ouabain, a known Na+/K+ -ATPase inhibitor, in the BCM vesicles but not in the BBM system. Nicotine, insulin, sodium fluoride and sodium arsenate were inhibitors for both the vesicles.

Effect of Ca(2+)-channel blockers, Ca(2+)-ionophore and increased pyrene excimer formation on the microsomal glucose-6-phosphatase

The dependence of microsomal glucose-6-phosphatase (G-6-Pase) activity on Ca2+ as well as the membrane lipid microviscosity was studied by the effect of Ca(2+)-channel blockers (namely verapamil and nifedipine), Ca(2+)-ionophore, A23187 and pyrene excimer formation. Channel blockers depressed the G-6-Pase and Ca(2+)-ATPase while the ionophore increased these activities. Dimethyl sulfoxide, a known membrane surface active agent showed no change. Ca(2+)-uptake into the membrane has expectedly been lowered by the channel blockers while the ionophores facilitated the ion flux. Excimer formation of the fluorescent probe, pyrene as an indicator of increased membrane fluidity, and microviscosity calculated from there on, showed that Ca(2+)- and lipid microenvironment in the membrane significantly influenced the activity of G-6-Pase. Membrane lipid composition such as phospholipid/cholesterol molar ratio which also indicates an increased membrane fluidity is markedly increased with the ionophore but decreased with the channel blockers, while protein/phospholipid ratio remained unchanged. Microsomal G-6-Pase is a multicomponent multifunctional protein. It is argued that Ca2+ may play the role of an obligatory cofactor not only for the hydrolysis of G-6-P (catalytic part of the enzyme) but also involved in the regulation of substrate and product transport in or out of the endoplasmic reticulum lumen.

Calcium channel antagonist verapamil modulates human spermatozoal functions

The effect of calcium channel blocker, verapamil (0.5-50 microM), has been studied in vitro in relation to certain spermatozoal functions in human ejaculates. Disruptive changes in the head and tail region of the spermatozoa, separation of heads from tails and coiling of the tail were observed. Motility was considerably reduced, while the pattern of motility also changed from rapid, linear progression to slow or sluggish linear or non-linear movement and finally to non-progressive motility, or even immotility. Verapamil significantly inhibited the influx of extracellular Ca2+. The study of kinetic effects further revealed a reduction in the maximum uptake velocity, but no change in the apparent substrate affinity constant. A highly significant decrease in Ca(2+)-dependent ATPase activity was also noted. In order to see whether this drug had any cytotoxic effect, presumably through lipid peroxides, thiobarbituric acid-reactive substances were measured. Verapamil produced an increase in the formation and release of malonyldialdehyde. The level of membrane cholesterol and phospholipid in the spermatozoa was also lowered considerably. The potential of such a calcium channel blocking agent in the designing of a male contraceptive programme is discussed.

Isolation & chemical composition of lung surfactant from human amniotic fluid

Lung surfactant was isolated from human amniotic fluid collected at term and studied with reference to the material isolated from human and rabbit lung lavage. The isolated material showed 58 per cent lipid by dry weight, 29 per cent protein and relatively smaller amounts of nucleic acids, sialic acid and hexose. Phosphatidyl choline was the predominant phospholipid species and accounted for 46 per cent of the total lipid by weight, followed by phosphatidyl glycerol (7%) and phosphatidyl ethanolamine (5%). Cholesterol was the major neutral lipid fraction present (10%) and was almost entirely in the free form. Other lipid fractions present in minor quantity were triglycerides, esterified cholesterol, phosphatidyl serine, phosphatidyl inositol and sphingomyelin. The material contained a very high degree of alkaline phosphatase activity, while other enzymes such as acid phosphatase, glucose-6-phosphatase, ATPases, 5'-nucleotidase and beta-N-acetyl glucosaminidase were also present.

The effect of nifedipine, a calcium channel blocker, on human spermatozoal functions

In vitro addition of 0.1-100 microns of a calcium channel blocker, Nifedipine, resulted in a significant non-competitive inhibition in the uptake of Ca++. The activity of Ca(++)-dependent ATPase enzyme was also decreased. Motility of the spermatozoa was significantly arrested following incubation with different doses of the drug at 37 degrees C for different durations. The pattern of motility changed within two hours from rapid and linear progression to slow or sluggish linear or non-linear movement and finally to non-progressive motility or even immotility. Scanning electron microscopic studies revealed disruptive changes in the head as well as tail region and coiling of spermatozoa after Nifedipine treatment. An increase in the formation and release of malonyldialdehyde was observed following Nifedipine addition in a dose-dependent fashion. The membrane cholesterol and phospholipid contents were considerably lowered in the treated samples. The potential of such calcium channel blocking agent in the designing of male contraceptive programme is discussed.

Changes in membrane-bound hydrolases by metronidazole in rat renal brush border

The antiprotozoal drug metronidazole, when administered orally at a dose level of 100 mg/kg body wt. daily for 7 days to rats, brought about significant elevation of renal brush-border-membrane-bound hydrolytic enzymes, such as alkaline phosphatase, maltase, sucrase, and leucine aminopeptidase (LAP). Kinetic analysis of the enzymes (substrate saturation) indicated that the drug produced an increase in the maximum of apparent initial enzyme velocity (Vmax), while the substrate affinity constant (Km) remained unaltered. These changes were not recovered to the normal level even after the drug regimen was stopped and the animals were allowed to recover for a period of 7 days. Lipid analysis of brush border membrane (BBM) revealed a significant elevation in the cholesterol, phospholipid, and ganglioside levels, while no marked change was recorded in triglyceride, free fatty acid and plasmalogen. Study of the temperature-dependent parameters of the enzymes showed that metronidazole induced a shift in the transition temperature (To) in LAP with nearly total reversibility in the recovery group. No such change was seen in the other enzymes. However, there also was a lowering in the energy of activation (Ea) below To, which returned to normal after the treatment was withdrawn.

Effect of sulfasalazine on adaptive and functional changes in intestine of normal and protein-calorie-malnourished rats

The effects of sulfasalazine (500 mg/kg body weight daily for 35 days) and its subsequent recovery for another 35 and 65 days have been investigated on the intestinal uptake of certain end-product nutrients, viz. glucose, leucine, alanine, and calcium, in normal and protein-calorie malnourished (PCM) male albino rats. Sulfasalazine administration caused a reduction in body weight in PCM animals, while intestinal weight and length as well as protein and nucleic-acid contents were reduced in both normal and PCM animals. Serum proteins also showed a decrease in PCM rats. PCM rats showed elevated levels of glucose, amino acids, and calcium uptake by the intestinal segments, but sulfasalazine feeding inhibited the uptake of nutrients both in normal-fed and malnourished animals. All these changes were found to be reversible after the withdrawal of drug treatment. Sulfasalazine caused a decrease in the Na(+)-dependent (active) glucose uptake as well as the Na(+)-independent (passive) process. The kinetic parameters of glucose uptake indicate that the drug might interfere with the transport/carrier protein of these nutrients, because reduction was observed in maximum uptake velocity (Jmax) of these systems without any change in the affinity constant (Kt).

Interaction of pulmonary surfactant-associated protein (SP-A) with surfactant lipids

A pulmonary surfactant-associated protein complex with components of 36, 32 and 28 kDa was isolated from human lung homogenates and reassembled with surfactant lipids prepared as small unilamellar liposomes. The role of divalent cations in the assembly of this recombinant lipoprotein complex was studied by monitoring the changes in turbidity, intrinsic tryptophanyl fluorescence and surface activity. The protein-facilitated lipid aggregation was promoted on addition of 5 to 20 mM Ca2+. Intrinsic fluorescence measurements on SP-A (28-36 kDa) indicated that the tryptophan side chains were in a relatively hydrophobic environment, that the wavelength of maximum fluorescence emission and also the relative fluorescence, were changed upon the binding of lipid. Tryptophanyl fluorescence of the lipoprotein assembly was quenched as indicated by a reduction in the effective Stern-Volmer constant. These results suggest that Ca2+ lipid-protein interactions are involved in the structure and function of extracellular lung surfactant assembly.

Immunoassay for the determination of surfactant apoprotein (SP-A) in human amniotic fluid: comparison with other indices of assessing foetal lung maturity

The concentration of the major surfactant-associated protein SP-A (28-36 kDa) was determined in 73 amniotic fluid samples obtained from normal (n = 40) and complicated (n = 33) pregnancies. Lecithin/sphingomyelin (L/S) ratio and phosphatidylglycerol (PG) levels were also determined in all the samples by one-dimensional step-wise thin-layer chromatography. An enzyme-linked immunosorbent assay was used to determine human lung surfactant apoprotein SP-A. The amount of SP-A in human amniotic fluid increased as a function of gestational age from 8 mg l-1 at 36 weeks to 11.75 mg l-1 at 40-41 weeks of gestation. There was a significant difference (p less than 0.01) in amniotic fluid SP-A concentration from female (9.93 +/- 0.60 micrograms ml-1) compared to male (9.10 +/- 0.52 micrograms ml-1) foetuses. In amniotic fluid samples obtained from a group of complicated pregnancies, SP-A levels were significantly lower than in the normal group when adjusted for gestational age and sex of the foetus (p less than 0.05).

Analysis of the major surfactant-associated proteins in human lung

The protein component of human pulmonary surfactant was analysed. A purified surfactant preparation, after delipidation, was subjected to gel filtration on Sephadex G-200. The proteins present in the surfactant were categorised by means of SDS-polyacrylamide gel electrophoresis into serum and non-serum components. Molecular masses determination showed the presence of three sub-groups with molecular masses of 60-68 kDa, 28-36 kDa and 10-18 kDa, respectively. Antiserum generated against 28-36 kDa protein strongly reacted with the purified surfactant and amniotic fluid, while it did not show any cross reactivity with other groups of proteins and serum in a double diffusion immunoprecipitation assay. We propose that this protein is the major non-serum surfactant-associated protein present in human lung surfactant.