Search PubMed⌕ Search

Biomedical subjects

R J Mason

Publications and source records attributed to R J Mason.

At least 127 records · Page 7Linked to original sources
PubMed1989

Lymphocyte populations in lung tissue, bronchoalveolar lavage fluid, and peripheral blood in rats at various times during the development of silicosis.

Inflammatory cells and lymphocyte populations were examined in the bronchoalveolar lavage (BAL) fluid, lung tissues, and peripheral blood from rats at various times after the intratracheal instillation of silica. In lavage fluid, there was a rapid initial increase in the percentage and number of polymorphonuclear leukocytes (PMN), which slowly decreased during the course of the experiment. In addition, compared to controls, there was an increased number and percentage of lymphocytes throughout the 75 days of the experiment. The lymphocytic populations, which were determined by an indirect immunofluorescence method with monoclonal antibodies to lymphocyte surface markers, showed a predominance of the T-helper phenotype from Day 14 through the end of the experiment (Day 75). The number of PMNs obtained from collagenase digest of the lung was increased over control levels up to Day 7 after silica administration and remained at a relatively constant level until Day 14, after which time they decreased slightly in number. The total number of lymphocytes peaked on Day 14, with cells of the T-helper phenotype predominating after this time. In the peripheral blood, T-helper cells from silicotic rats were significantly increased over control rats on Days 7 and 14 but returned to normal control values after this time. The lymphocyte subsets in the BAL, but not in the peripheral blood, more closely reflect the lymphocyte patterns in the lung. The results of these experiments suggest that T-helper cells may play an important role in the inflammatory-fibrotic events in the lungs of rats with silicosis.

Animals↗
PubMed1989

Bronchoalveolar lavage fluid from normal rats stimulates DNA synthesis in rat alveolar type II cells.

Proliferation of alveolar type II cells after lung injury is important for the restoration of the alveolar epithelium. Bronchoalveolar lavage fluid (BALF) may represent an important source of growth factors for alveolar type II cells. To test this possibility, BALF fluid was collected from normal rats, concentrated 10-fold by Amicon filtration, and tested for its ability to stimulate DNA synthesis in rat alveolar type II cells in primary culture. BALF induced a dose-dependent increase in type II cell DNA synthesis resulting in a 6-fold increase in [3H]thymidine incorporation. Similar doses also stimulated [3H]thymidine incorporation into rat lung fibroblasts by 6- to 8-fold. Removal of pulmonary surface active material by centrifugation did not significantly reduce the stimulatory activity of BALF for type II cells. The stimulation of type II cell DNA synthesis by BALF was reduced by 100% after heating at 100 degrees C for 10 min, and by approximately 80% after reduction with dithiothreitol, and after trypsin treatment. Dialysis of BALF against 1 N acetic acid resulted in a 27% reduction in stimulatory activity. The effect of BALF in promoting type II cell DNA synthesis was more pronounced when tested in the presence of serum, although serum itself has very little effect on type II cell DNA synthesis. When BALF was tested in combination with other substances that stimulate type II cell DNA synthesis (cholera toxin, insulin, epidermal growth factor, and acidic fibroblast growth factor), additive effects or greater were observed. When BALF was chromatographed over Sephadex G150, the activity eluted with an apparent molecular weight of 100 kDa.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Alveolar type II cells, surfactant protein A (SP-A), and the phospholipid components of surfactant in acute silicosis in the rat.

Silica instillation causes a massive accumulation of surfactant phospholipids and the appearance of hypertrophic type II cells in the rat. We have examined the metabolic consequences of silica instillation with a special emphasis on surfactant protein A (SP-A), the major glycoprotein of surfactant. Fourteen days after instillation of 10 mg of silica, the amount of phospholipids in lavage increased 14-fold and the amount of SP-A increased 10-fold. The phospholipid composition of lavage material from silica-treated animals was altered by a reduction in the percentage of phosphatidylglycerol and an increase in phosphatidylinositol. The percentage of saturated phosphatidylcholine did not change. Type II cells isolated from rats treated with silica could be separated into cells of normal size and of increased size by centrifugal elutriation. There was an increase in phospholipid and SP-A content in the larger type II cells isolated from silica-treated rats relative to type II cells from control rats (by 45% and 70%, respectively, when expressed per micrograms protein; p less than 0.01). Activities of the phospholipid biosynthetic enzymes cholinephosphate cytidyltransferase, lysophosphatidylcholine acyltransferase, and phosphatidylglycerol phosphate synthetase increased (nmol/min/mg cell protein) in the hypertrophic type II cells relative to type II cells from control rats (by 40%, 112%, and 95%, respectively, p less than 0.05). Incorporation of (1-14C)-acetate was also increased in hypertrophic type II cells relative to type II cells from control rats (by 43%, p less than 0.05). The only difference in the distribution of acetate incorporated into individual lipids was a slight increase in the percentage incorporated into phosphatidylinositol. Although the increase in phosphatidylcholine found in the lavage could be due to increased synthesis as reflected by the changes in enzymatic activity and rate of acetate incorporation, the reduction in phosphatidylglycerol in lavage and in type II cells could not be explained simply by a reduction in synthesis on the basis of available data. There was a marked increase in SP-A content in lavage and in type II cells isolated from silica-treated rats without a significant change in the relative abundance of SP-A mRNA. This dissociation of SP-A mRNA abundance and apoprotein content suggests that factors other than transcription may be important for the observed accumulation of SP-A in silica-treated rats. We conclude that the phospholipidosis and proteinosis that occur subsequent to silica instillation in the rat lung are not solely attributable to increase in the rates of synthesis of these components.

Acute Disease↗
PubMed1989

Effects of two extracellular matrices on morphologic and biochemical properties of human type II cells in vitro.

Previous observations have suggested that differentiated functions of adult rat type II alveolar cells are affected in part by cell-matrix interactions. We examined several aspects of differentiated adult human type II cells cultured on either bovine corneal endothelial cell extracellular matrix (BCECM) or matrix derived from the Englebreth-Holm-Swarm tumor (EHS). Compared to cells cultured on BCECM, adult human type II cells grown on EHS assumed a more cuboidal shape, had a more defined apical-basal polarity, and appeared to contain a greater number of lamellar bodies and neutral lipid inclusions. These cells also incorporated a greater percentage of [14C]acetate into saturated phosphatidylcholine (SPC) than did their counterparts grown on BCECM. In contrast, the relative incorporation of [14C]acetate into phosphatidylglycerol (PG) was lower in cells grown on EHS than cells cultured on BCECM. The histochemical stain for alkaline phosphatase was useful in identification of human type II cells. Alkaline phosphatase expression was elevated in cells cultured on EHS compared to those cultured on BCECM. These results suggest that maintenance of a differentiated morphology, lipid synthesis, and expression of alkaline phosphatase activity by primary cultures of adult human type II cells are also influenced by cell-matrix interactions. All markers of differentiated function of type II cells except synthesis of PG are better maintained on EHS than on BCECM. Under the conditions of these experiments, synthesis of SPC and PG appears to be independently regulated.

Alkaline Phosphatase↗
PubMed1989

Properties of isolated nonciliated bronchiolar cells from mouse lung.

Nonciliated bronchiolar cells (Clara cells) are thought to provide important respiratory secretions in the small airways and to have other metabolic functions. In mice, nonciliated bronchiolar cells have been the subject of special investigation because tumors of these cells can be specifically induced by chemical carcinogens. A method for isolating nonciliated bronchiolar cells from mice has been reported. However, we have developed a method to isolate these cells from the lungs of BDF1 mice with approximately 80% purity. Cells were identified by electron microscopy, nitroblue tetrazolium dye reduction in the presence of NADPH, immunocytochemical staining of cytochrome P450 isozymes, and mitochondrial staining with rhodamine 123. The isolated cells were examined in culture for synthesis and secretion of proteins and phospholipids. Protein synthesis and secretion were examined in cells labeled with [34S]methionine for 16 h. Fresh medium was added to washed cells and the cells were incubated for an additional 3h. The secreted proteins were precipitated with 10% trichloroacetic acid. Molecular weights of the most prominent radiolabeled secreted proteins were 6, 36, 43, and 45 kDa. Phospholipid synthesis and secretion were examined in cells labeled with [14C]acetate and 32P. Less than 1% of the radioactive lipids was found in the medium, and secretion of lipid was not stimulated by terbutaline or tetradecanoylphorbol acetate compounds, which stimulate phospholipid secretion by type II cells. These data support the hypothesis that nonciliated bronchiolar cells synthesize and secrete proteins but do not secrete phospholipids in any appreciable amount.

Animals↗
PubMed1989

Monoclonal antibodies specific for antigens expressed by rat type II alveolar epithelial and nonciliated bronchiolar cells.

Markers specific for various lung cells are useful for studies of cellular differentiation and function. We have produced monoclonal antibodies that bind to isolated rat type II alveolar epithelial cells in an ELISA. Two such antibodies, 2C1 and 3F9, specifically labeled type II cells and nonciliated bronchiolar cells by indirect immunofluorescence of rat lung. A third antibody, 2A3, recognized isolated type II cells by ELISA and immunofluorescence, but did not bind to sections of whole lung. Further immunofluorescence studies on adult rat tissue showed that neither 2C1 nor 3F9 labeled other lung cells or cells in kidney, small intestine, brain, or trachea. The antigen or antigens recognized by 2C1 and 3F9 was not detectable at day 15 of fetal lung gestation but was detectable by day 21. Immunofluorescence studies carried out on 0.5-microns frozen sections of lung tissue demonstrated that both 2C1 and 3F9 bound to cell surface antigens, which are expressed in a highly polarized fashion on the luminal surface of the alveolus and bronchiole. The rat cell line, L2, which displays some similarities to type II cells, did not display positive immunofluorescence to 2A3, 2C1, or 3F9. The antibodies 2C1 and 3F9 are distinct from and apparently more specific than previously described monoclonal antibodies raised to rat type II cells. Alveolar type II and nonciliated bronchiolar cells share several common features. Both cell types contain the surfactant apoprotein SP-A, proliferate in response to lung injury, develop in the late stages of gestation, take up and catabolize platelet-activating factor, contain high levels of cytochrome P-450, and can be induced to form tumors in response to chemical carcinogens. The recognition of highly specific surface antigen(s) on both nonciliated bronchiolar cells and type II cells demonstrates yet another characteristic shared by the two cell types.

Animals↗
PubMed1989

Increased expression of class II antigens of the major histocompatibility complex on alveolar macrophages and alveolar type II cells and interleukin-1 (IL-1) secretion from alveolar macrophages in an animal model of silicosis.

Silicosis is a chronic progressive granulomatous and fibrotic lung disease caused by inhaled silica. Although the causative agent is known, the pathogenesis, especially the immunologic response, is not well understood. We examined two important components of cell-mediated immune responses in the lungs of rats with silica-induced lung disease, i.e., class II (Ia) antigen expression and IL-1 production. The relative density of Ia was examined on isolated alveolar macrophages and type II cells with a solid-phase cellular radioimmunoassay and the percent of Ia positive cells was determined by an indirect immunofluorescent technique. There was a three-fold increase of Ia expression on the alveolar macrophages and nearly a two-fold increase on type II cells from rats with silicosis compared to normal rats. The percent of alveolar type II cells positive for Ia increased by 20%, and the alveolar macrophages increased by 40%. IL-1 in supernatants from cultured alveolar macrophage was measured by the amount of DNA synthesis in an IL-1 dependent cell line (D10). A six-fold increase in IL-1 secretion was noted in macrophage supernatants derived from silica-treated animals. We conclude that in this animal model of silicosis, a local amplification of cell-mediated immune responses may be instrumental in the pathogenesis.

Animals↗
PubMed1988

Chemical modification of surfactant protein A alters high affinity binding to rat alveolar type II cells and regulation of phospholipid secretion.

Alveolar type II cells express a high affinity receptor for pulmonary surfactant protein A (SP-A), and the interaction of SP-A with these cells leads to inhibition of surfactant lipid secretion. We have investigated the binding of native and modified forms of SP-A to isolated rat alveolar type II cells. Native and deglycosylated forms of SP-A readily competed with 125I-SP-A for cell surface binding. Alkylation of SP-A with excess iodoacetamide yielded forms of SP-A that did not inhibit surfactant lipid secretion and did not compete with 125I-SP-A for cell surface binding. Reductive methylation of SP-A with H2CO and NaCNBH3 yielded forms of SP-A with markedly reduced receptor binding activity that also exhibited significantly reduced capacity to inhibit lipid secretion. Modification of SP-A with cyclohexanedione reversibly altered cell surface binding and the activity of SP-A as an inhibitor of lipid secretion. Two monoclonal antibodies that block the function of SP-A as an inhibitor of lipid secretion completely prevented the high affinity binding of SP-A to type II cells. A monoclonal antibody that recognizes epitopes on SP-A but failed to block the inhibition of secretion also failed to completely attenuate high affinity binding to the receptor. Concanavalin A inhibits phospholipid secretion of type II cells by a mechanism that is reversed in the presence of excess alpha-methylmannoside. Concanavalin A did not block the high affinity binding of 125I-SP-A to the receptor. Neither the high affinity binding nor the inhibitor activity of SP-A was prevented by the presence of mannose or alpha-methylmannoside. The SP-A derived from humans with alveolar proteinosis is a potent inhibitor of surfactant lipid secretion but failed to completely displace 125I-SP-A binding from type II cells. From these data we conclude that: 1) cell surface binding activity of rat SP-A is directly related to its capacity to inhibit surfactant lipid secretion; 2) monoclonal antibodies directed against SP-A can be used to map binding domains for the receptor; 3) the lectin activity of SP-A against mannose ligands does not appear to be essential for cell surface binding; 4) concanavalin A does not compete with SP-A for receptor binding; and 5) the human SP-A derived from individuals with alveolar proteinosis exhibits different binding characteristics from rat SP-A.

Animals↗
PubMed1988

Improved maintenance of adult rat alveolar type II cell differentiation in vitro: effect of hydrocortisone and cyclic AMP.

We have examined the effect of hydrocortisone and cyclic AMP on the maintenance of lipid synthesis in primary cultures of adult rat alveolar type II cells. These hormones were tested in the presence of either 1% or 5% charcoal-stripped rat serum (CS-rat serum). The effect of substratum on responsiveness to these hormones was evaluated by comparing cells cultured for 4 days on tissue culture plastic, on floating type I collagen gels, on rat lung fibroblast feeder layers on floating collagen gels (floating feeder layers), and on Engelbreth-Holm-Swarm (EHS) tumor basement membrane gels. Type II cells cultured on floating feeder layers in medium containing 1% CS-rat serum and 10(-5) M hydrocortisone plus 0.5 mM dibutyryl cyclic AMP exhibited significantly increased incorporation of [14C]acetate into total lipids (238% of control). The hormone combination also increased the relative percentage of acetate incorporated into phosphatidylglycerol (PG; 7.3% versus 1.9%) and saturated phosphatidylcholine (PC; 43.6% versus 37.6%). The percentage of acetate incorporated into neutral lipids was significantly decreased by the addition of hormones (28.6% versus 70.0%). The addition of hydrocortisone and cyclic AMP to medium containing 5% CS-rat serum resulted in an increase in the relative incorporation of acetate into saturated PC (51.2% versus 46.4%), but had no effect on the relative incorporation of acetate into PG or on the incorporation of acetate into total lipids. Type II cells cultured on EHS gels in medium containing 1% CS-rat serum plus hydrocortisone and cyclic AMP showed increased acetate incorporation into total lipids (204% of control) and a relative decrease in the percentage of acetate incorporated into neutral lipids (16.9% versus 47.0%). The hormone combination also increased the relative incorporation of acetate into PG (4.4% versus 2.5%) and saturated PC (49.9% versus 42.1%). Hydrocortisone and cyclic AMP added to medium containing 5% CS-rat serum concentration increased the relative incorporation of acetate into saturated PC by type II cells on EHS gels, but these additions had no effect on acetate incorporation into PG. No responses to these soluble factors were seen when type II cells were cultured on floating type I collagen gels without feeder layers or on tissue culture plastic. These data indicate that there are positive interactions between substratum, soluble factors and serum in the maintenance of differentiated function of adult rat alveolar type II cells in vitro.

Animals↗
PubMed1988

Rat pulmonary surfactant protein A is expressed as two differently sized mRNA species which arise from differential polyadenylation of one transcript.

In rat, the surfactant-associated glycoprotein A, SP-A, is encoded by two mRNA species of 0.9 and 1.6 kb. Each transcript is polyadenylated and is found in approximately the same ratio in total cellular RNA isolated from either alveolar type II cells or from whole lung. The two mRNA species have identical coding regions and differ only in the length of the 3' untranslated sequences. Restriction analysis and partial sequence analysis of rat genomic clones indicate that each mRNA species arises from one gene, with the difference in size most easily accounted for by differential polyadenylation. During fetal development, the accumulation of mRNA encoding SP-A is detectable by day 18 but increases many-fold on day 19. However, there are no apparent alterations in the prevalence of either mRNA species during fetal development or in the early postnatal period.

Amino Acid Sequence↗
PubMed1988

The Na+/H+ antiporter in rat alveolar type II cells and its role in stimulated surfactant secretion.

We used the pH-sensitive fluorescent probe 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) to identify Na+/H+ exchange in freshly isolated rat alveolar type II cells and alveolar type II cells in primary culture. The intracellular pH (pHi) of freshly isolated alveolar type II cells was 7.36 +/- 0.05 (n = 3). When freshly isolated alveolar type II cells were acid loaded with nigericin in sodium-free buffer, the pHi dropped to 6.59 +/- 0.04 and remained low in sodium-free buffer. When acid-loaded cells were subsequently incubated with NaCl, pHi increased in a dose-dependent manner. Amiloride (0.1 mM) inhibited the sodium-induced increase in pHi. When the acid-loaded cells were resuspended in an unbuffered choline chloride solution, the cells secreted H+ in a sodium-dependent and amiloride-inhibitable manner. Alveolar type II cell monolayers, which were cultured for 22 h on glass coverslips and then loaded with BCECF, had a resting pHi of 7.48 +/- 0.05 (n = 4). Nigericin acidified these cultured cells in the absence of sodium and NaCl increased the pHi of these acid loaded cells as observed in freshly isolated cells. Secretagogues of pulmonary surfactant, 12-O-tetradecanoylphorbol 13-acetate (TPA) and terbutaline, did not change pHi. Inhibition of the Na+/H+ antiporter by the addition of amiloride to a Na+ containing medium or the substitution of choline for Na+ did not inhibit stimulated phosphatidylcholine secretion. We conclude that pHi regulation in rat alveolar type II cells is in part mediated by an amiloride-sensitive Na+/H+ antiporter, but this system appears not to be involved in TPA- or terbutaline-induced pulmonary surfactant secretion in primary culture.

Amiloride↗
PubMed1988

Pulmonary surfactant apoprotein A structure and modulation of surfactant secretion by rat alveolar type II cells.

The pulmonary surfactant apoprotein with a reduced denatured molecular mass of 26-38 kDa (PSP-A) has recently been identified as an inhibitor of surfactant phospholipid secretion by isolated rat alveolar type II cells. We have investigated some of the structural determinants of PSP-A that are relevant to the inhibitory process. The PSP-A was isolated from rats given an intratracheal instillation of silica. The yield of PSP-A from silica-treated animals was 20-40-fold higher than that obtained from untreated animals. Reduction of PSP-A with 2-mercaptoethanol caused a reversible loss of biological activity that was restored by mild oxidation. Alkylation of the protein with excess iodoacetamide also led to inactivation, although titration with 5,5'-dithiobis-(2-nitrobenzoic acid) indicated that the protein initially contained no free sulfhydryl moieties. Neither alkylation nor reduction plus alkylation completely prevented the formation of oligomers as determined by gel permeation analysis. The apparent molecular mass of PSP-A at 4 degrees C in low ionic strength buffers was 1.6 megadaltons, and at 37 degrees C in normal ionic strength buffers was greater than 1.5 megadaltons. Removal of the oligosaccharide moiety with endoglycosidase F also had no effect upon biological activity. Five distinct monoclonal antibodies recognizing peptides epitopes on PSP-A were produced. All monoclonal antibodies exhibited similar affinity for PSP-A and recognized the delipidated and deglycosylated form. Four monoclonal antibodies reacted with epitopes on PSP-A that altered its function as an inhibitor. One monoclonal antibody was clearly ineffective at altering the activity of PSP-A. These results demonstrate that: 1) disulfide bonds are required for the activity of PSP-A, 2) disruption of disulfides does not prevent the formation of oligomeric forms of PSP-A, 3) the oligosaccharide moiety is not essential for biological activity, and 4) monoclonal antibodies can be used to map the epitopes responsible for biological activity.

Alkylation↗
PubMed1988

Mini-P1 plasmid replication: the autoregulation-sequestration paradox.

It has been proposed that the initiator protein RepA is rate limiting for mini-P1 plasmid replication, and that the role of the plasmid copy number control locus is to sequester the initiator and thus reduce replication. This proposal appears inconsistent with the observation that RepA is autoregulated, since the protein lost by sequestration should be replenished. A resolution of this autoregulation-sequestration paradox is possible if the sequestered RepA, unavailable for replication, is still available for promoter repression. We demonstrate that RepA binds to the control locus and to the promoter region simultaneously, causing the intervening DNA to loop. DNA looping could provide the requisite mechanism by which RepA bound to the control locus might exert repression.

DNA Helicases↗
PubMed1988

Passive avoidance learning produces focal elevation of bursting activity in the chick brain: amnesia abolishes the increase.

Presentation of a bright bead to day-old chicks (Gallus domesticus: Ross 1 Chunky Chicks) elicits spontaneous pecking. If the bead is coated with an aversive substance (e.g., methylanthranilate), they will avoid similar beads subsequently; if it is coated with water, they peck avidly on re-presentation. Formation of a memory for this one-trial passive avoidance task is unaffected by subconvulsive transcranial electroshock when applied 10 min after training in 60% of birds, whereas "immediate" post-training electroshock renders 63% of chicks amnesic. Memory formation and retention is associated with a large bilateral enhancement in trained over control chicks (320 and 350% in left and right hemispheres, respectively; p less than 0.001) of a particular spontaneous multi-unit activity firing pattern, that is, short-duration (15-40 ms) bursts of large-amplitude (greater than or equal to 200 microV, 450 microV max p-p), high-frequency (400-450 Hz) spiking in anesthetized chicks. This effect is observed in data lumped from 1-13 h after training and is restricted to the intermediate medial hyperstriatum ventrale. When chicks are rendered amnesic by electroshock immediately following training, there is a complete abolition of this increase in burst firing; in those chicks where this treatment fails to elicit amnesia, the increase in bursting is still observed. In birds in which the shock is delayed and memory formation occurs, the increase in bursting activity is maintained; however, if the delayed shock produces apparent amnesia, then the increase is once again abolished. The electroshock had no effect on bursting per se in untrained chicks. There was no significant difference in tonic spiking between the chicks. A marked increase in the occurrence of bursting epochs in the IMHV of anesthetized chicks following passive avoidance training is therefore closely associated with memory formation, but not with the nonspecific concomitants of the training procedure.

Amnesia↗
PubMed1988

Alveolar type II cells express a high-affinity receptor for pulmonary surfactant protein A.

Primary cultures of rat alveolar type II cells bind radiolabeled pulmonary surfactant protein A (SP-A) with high affinity. The binding of 125I-labeled SP-A is time- and temperature-dependent and is not accompanied by significant degradation. The binding process is saturable at low concentrations of SP-A (5 micrograms/ml), and unlabeled SP-A readily competes with labeled SP-A for cellular binding sites. Subsequent to binding, two pools of cell-associated 125I-labeled SP-A can be identified based upon sensitivity to trypsin at 0 degrees C. It is likely that the trypsin-sensitive pool comprises 125I-labeled SP-A bound to the cell surface and the trypsin-insensitive pool comprises the internalized protein. Scatchard analysis of cell surface binding of SP-A at 0.1-10 micrograms/ml shows positive cooperativity at concentrations between 0.1 and 1 micrograms/ml. Hill plots give nH = 1.34 +/- 0.08 with an apparent dissociation constant K'd = 1.02 +/- 0.32 micrograms/ml (which is 0.64 +/- 0.19 nM if the native molecular mass of oligomeric SP-A is assumed to be 1.6 MDa). The binding of SP-A to type II cells shows an absolute requirement for Ca2+. The putative receptor for SP-A is unaffected by treatment of type II cells with a variety of proteases and N-Glycanase (EC 3.5.1.52). Alveolar macrophages also exhibit high-affinity binding of SP-A, but rat lung fibroblasts and the alveolar epithelial cell line L2 exhibit only nonspecific binding.

Animals↗
PubMed1988

Role of intracellular glycerol-3-phosphate in the synthesis of phosphatidylglycerol by freshly isolated adult rat alveolar type II cells.

Synthesis of phosphatidylglycerol and phosphatidylinositol, phospholipid components of pulmonary surfactant, use the same precursor, CDP-diacylglycerol. In alveolar type II epithelial cells, extracellular myoinositol has been used to suppress phosphatidylglycerol synthesis, presumably by competing with glycerol-3-P for a common pool of CDP-diacylglycerol. We sought to see if extracellular lactate would increase acetate incorporation into phosphatidylglycerol by increasing glycerol-3-P. Lactate and 10 mM cytidine increased acetate incorporation into phosphatidylglycerol, whereas myoinositol and pyruvate decreased acetate incorporation into phosphatidylglycerol. Lactate increased the intracellular content of glycerol-3-P. We conclude that phosphatidylglycerol synthesis can, in part, be regulated by intracellular glycerol-3-P concentration, and we speculate that extracellular (alveolar) lactate may increase glycerol-3-P concentration in alveolar type II cells in vivo.

Animals↗