Choline phosphokinase, phosphorylcholine cytidyltransferase and CDP-choline: 1,2-diglyceride cholinephosphotransferase activity in developing rat lung

Development of cholinephosphotransferase in guinea pig lung mitochondria and microsomes

Development of mitochondrial and microsomal choline phosphotransferase in the fetal guinea pig lung was investigated. The activity in fetal mitochondria was more than twice of that in fetal microsomes. However, in adult lung, the enzyme was distributed mostly in microsomes. In fetal lung, both the mitochondrial and microsomal enzyme activity was greatest at approx. 81% of the total gestation period (55 days). The specific activity in the microsomal fraction than declined until term, but increased again in the 24-h newborn from 1.0 to 2.3 nmol/min per mg protein. The activity in the mitochondrial fraction declined after 61 days (2.8 nmol/min per mg) to a minimal level at term (0.6 nmol/min per mg). Although the enzyme activity decreased from day 55 (1.2 nmol/min per mg), the amount of phosphatidylcholine gradually increased between day 55 and term.

Phosphatidylcholine synthesis and glycogen depletion in fetal mouse lung: developmental changes and the effects of dexamethasone

We measured the rate of choline incorporation into phosphatidylcholine in lung slices; the glucogen content of the lung; and the activities of pulmonary cholinephosphate cytidylyltransferase, cholinephosphotransferase and phosphatidate phosphatase in the mouse during late fetal and early postnatal development. We also examined the effect of maternal dexamethasone administration on these parameters of fetal lung maturation. There was a development increase in the rate of choline incorporation between 17 days gestation (term is 19 days) and the immediate newborn period. There was also a developmental decrease in the glycogen content of the lung but this did not occur until 18 days. There was a developmental increase in the activities of cholinephosphate cytidylytransferase and phosphatidate phosphatase but little change in the activity of cholinephosphotransferase. Dexamethasone doubled the rate of choline incorporation into phosphatidylcholine at 17 and 18 days gestation. It decreased the glycogen content of the fetal lung by 74% at 18 and 19 days, but had no effect at 16 and 17 days. Dexamethasone increased the activity of pulmonary cholinephosphate cytidylyltransferase by 37% and that of cholinephosphotransferase by 27% at 17 days. It increased the activity of phosphatidate phosphatase by 25% at 16 days and by 32% at 19 days. These data show that the normal development profile of these parameters of fetal lung maturation in the mouse, as well as the effects of glucocorticoids thereon, are generally similar to those in the rabbit and rat. However, stimulation of cholinephosphotransferase by glucocorticoids has not been generally observed in other species. Furthermore, since the changes in the rate of choline incorporation precede those in glycogen depletion, the data suggest that the relationship between phospholipid synthesis and glycogen degradation is not simply that of precursor to product.

Pool sizes of the precursors for phosphatidylcholine synthesis in developing rat lung

1. Pulmonary maturation in the rat is accompanied by a 30% postnatal increase in the pool size of choline, a 4-fold overall prenatal and postnatal decrease in the level of cholinephosphate, a 3-fold decrease in CDPcholine levels and a 2-fold increase in the content of phosphatidylcholine. 2. The level of 1,2-diacyl-sn-glycerol in rat lung increases 5-fold during the fetal and neonatal periods. Only minor alterations were noted in the fatty acid composition. 3. These results are consistent with an increase in the relative rates of the cholinephosphate cytidylyl-transferase and cholinephosphotransferase steps of phosphatidylcholine production during pulmonary maturation. The relative rate of the step catalyzed by phosphatidate phosphohydrolase may also be increased.

Phospholipids of the lung in normal, toxic, and diseased states

The highly pulmonary concentration of 1,2-dipalmitoyl-sn-glycerol-3-phosphorylcholine (dipalmitoyllecithin) and its implication as an important component of lung surfactant have promoted investigation of phospholipid metabolism in the lung. This review will set the contents including recent informations for better understanding of phospholipid metabolism of the lung in normal state (physiological significances of lung phospholipids, characteristics of phospholipids in lung tissue and alveolar washing, biosynthetic pathways of dipalmitoyllecithin, etc.) as well as in toxic states (pulmonary oxygen toxicity, etc.) and in diseased states (idiopathic respiratory distress syndrome, pulmonary alveolar proteinosis, etc.) Since our main concern has been to clarify the most important route for supplying dipalmitoyllecithin, this review will be focused upon the various biosynthetic pathways leading to the formation of different molecular species of lecithin and their potential significance in the normal, toxic, and diseased lungs.

Postnatal development of rat lung. Changes in lung lectin, elastin, acetylcholinesterase and other enzymes

The development of rat lung from a primitive gas-exchange organ to the mature respiratory organ is in large part a postnatal phenomenon that has been well characterized by morphological and morphometric methods. The alveolarization of the lung is achieved during the first 3 weeks of life. Cholinergic innervation of rat lung also appears postnatally. We have monitored the presence or activity of several proteins during postnatal rat lung development. Newborn-rat lung contains negligible amounts of acetylcholinesterase, but the specific activity of acetylcholinesterase reaches adult values by postnatal day 10-11. Neonatal-rat lung does not contain significant amounts of beta-galactoside-binding protein [Powell (1980) Biochem. J.187, 123-129]. The activity of this endogenous lung lectin was apparent at about day 6, was maximal between days 10 and 13 before declining 8-10-fold to reach adult values. Elastin has been implicated from morphological evidence as critical to lung restructuring. We have quantified the amount of desmosine and isodesmosine per g wet wt. of lung. The concentration of elastin, by this criterion, was low and stationary until postnatal day 7; a dramatic increase in elastin concentration occurred between days 10 and 20, when adult values were reached. The peak of lung-lectin activity was coincident with the maturation of acetylcholinesterase and the beginning of rapid elastin cross-linking. The specific activities of angiotensin-converting enzyme, carbonic anhydrase, choline kinase and glucose 6-phosphate dehydrogenase were also monitored.

Phosphatidate phosphatase: activity and properties in fetal and adult rat lung

The purpose of this work is to compare the properties of phosphatidate phosphatase (L-alpha-phosphatidate phosphohydrolase, EC 3.1.3.4) in fetal and adult rat lung and to establish the developmental profile of activity measured under optimal conditions. The maximal pH of 6.0--7.0 and the inhibition by fluoride, Ca2+ and detergents were simialr for both adult and fetal. Phosphatidate phosphohydrolase activity was located in both mitochondria and microsomes. The localizations of marker enzymes indicated that the activity in these subfractions was not a result of cross contaminations. Very low activity was detected in the supernatant fraction and no Mg2+ requirement was demonstrable. The activity in the particulate fraction was about 50% of the adult from 18 day gestation until birth. Following birth, the activity rapidly increased to adult levels. Dipalmitoyl, dioleoyl and diacyl glycerol 3-phosphates are all utilized well as substrates. 1,2-dipalmitoyl-sn-glycerol 3-phosphate was hydrolyzed faster under maximal conditions. The velocity-substrate curves tended to be sigmoidal, particularly when 1,2-dipalmitoyl-sn-glycerol 3-phosphate was the substrate. Estimated apparent Km values of 0.02--0.03 mM were obtained for fetal and adult preparations.

Development of glycogen and phospholipid metabolism in fetal and newborn rat lung

Glucose, a major metabolic substrate for the mammalian fetus, probably makes significant contributions to surface active phospholipid synthesis in adult lung. We examined the developmental patterns of glycogen content, glycogen synthase activity, glycogen phosphorylase activity and glucose oxidation in fetal and newborn rat lung. These patterns were correlated with the development of phosphatidylcholine synthesis, content and the activities of enzymes involved in phosphatidylcholine synthesis. Fetal lung glycogen concentration increased until day 20 of gestation (term is 22 days) after which it declined to low levels. Activity of both glycogen synthase I and total glycogen synthase (I + D) in fetal lung increased late in gestation. Increased lung glycogen concentration preceded changes in enzyme activity. Glycogen phosphorylase a and total glycogen phosphorylase (a + b) activity in fetal lung increased during the period of prenatal glycogen depletion. The activity of the pentose phosphate pathway, as measured by the ratio of CO2 derived from oxidation of C1 and C6 of glucose, declined after birth. Fetal lung total phospholipid, phosphatidycholine and disaturated phosphatidylcholine content increased by 60, 90 and 180%, respectively, between day 19 of gestation and the first postnatal day. Incorporation of choline into phosphatidylcholine and disaturated phosphatidylcholine increased 10-fold during this time. No changes in phosphatidylcholine enzyme activities were noted during gestation, but both choline phosphate cytidylyltransferase and phosphatidate phosphatase activity increased after birth. The possible contributions of carbohydrate derived from fetal lung glycogen to phospholipid synthesis are discussed.

Activity and properties of CTP: cholinephosphate cytidylyltransferase in adult and fetal rat lung

Cholinephosphate cytidylyltransferase (CTP : cholinephosphate cytidylyltransferase, EC 2.7.7.15) is located in both the microsomal and supernatant fractions of adult lung when the tissue is homogenized in 0.145 M NaCl. The activity is located predominantly in the supernatant fraction in fetal lung. Cholinephosphate cytidylyltransferase in the supernatant from fetal lung is stimulated 4- to 6-fold by the additions of total lung lipid. Serine phosphoglycerides and inositol phosphoglycerides specifically caused stimulation whereas choline phosphoglycerides and ethanolamine phosphoglycerides produced no stimulation. Lysophosphatidylcholine cause some stimulation, but only at high concentrations. A number of detergents were investigated. All produced inhibition except for the ampholytic detergent, miranol H2M which was not inhibitory. None of the detergents produced any stimulation of activity. Cytidylyltransferase activity in fetal lung when assayed in the absence of lipid is about 25% of the adult. The activity when assayed in the presence of lipid is equal or slightly higher than adult levels. The activity, measured without added phospholipid, increases 5- to 6-fold within 12 h after birth, to values higher than in the adult. The activity, measured in the presence of phospholipid, increased almost linearly from -2 day until +1 day. There is an inverse relationship between the concentration of phospholipid in the fetal lung supernatant and the degree of lipid stimulation. Chromatographic experiments with Biogel A 1.5 columns have shown that cytidylyltransferase can exist in two molecular sizes, a small molecular size that requires phospholipid for activity, and a larger molecular weight species which does not require the addition of phospholipid for activity. Fetal lung has a higher proportion of the low molecular weight form than adult lung. The small molecular weight species can be converted to the larger molecular weight form by the addition of phospholipids.

Phospholipid content, composition and biosynthesis during fetal lung development in the rabbit

The phospholipid content and composition of lung wash and lung tissue as well as the activities of the enzymes involved in the synthesis of phosphatidylcholine and phosphatidylglycerol (the major surface active components of pulmonary surfactant) were studied in the rabbit during fetal lung development. In lung wash the amount of phospholipid increased four-fold during the period 27-31 day's gestation. There was a further ten-fold increase following the onset breathing. During the same period the amount of phosphatidylcholine in lung wash increased from 29% of the total phospholipid to 80% while the amount of sphingomyelin decreased from 38% to 2%. The amount of phosphatidylcholine in lung tissue also increased during development but to a much lesser extent. During fetal lung development the activities of choline kinase and cholinephosphate cytidyltransferase changed little, cholinephosphotranserase decreased while lysophosphatidic acid acyltransferase and lysolecithin acyltransferase increased. There was a postnatal increase in the activities of cholinephosphate cytidyltransferase, cholinephosphotransferase and both acyltransferases. The amount of phosphatidylglycerol, as a percentage of the total phospholipid, in lung wash and lung tissue as well as the activity of pulmonary glycerolphosphate phosphatidyltransferase did not change appreciably during development.