Role of myoinositol in regulation of surfactant phospholipids in the newborn

245

Early Human Development, 10 (1985) 245-254 Elsevier

EHD 00599

Role of myoinositol in regulation of surfactant phospholipids in the newborn Mikko Hallman, Ola D. Saugstad, Richard P. Porreco, Benita L. Epstein and Louis Gluck Department of Pediatrics, School of Medicine, University of California, San Diego, L.a Jolla, California, U.S.A., and Children’s Hospital, University of Helsinki, Helsinki, Finland Accepted for publication

29 May 1984

Summary

According to animal studies myoinositol decreases surfactant phosphatidylglycerol and increases phosphatidylinositol. In the present study lung effluent phospholipids and serum myoinositol were analyzed in respiratory distress syndrome (RDS, 19 cases), in other lung disease (6 cases) and in 22 newborn with no lung disease. In addition, myoinositol was studied in amniotic fluid and in serum from umbilical vessels and from maternal vein (15 healthy newborn). There was a significant correlation between the fetal and amniotic fluid levels of myoinositol, but no detectable correlation between fetal and maternal myoinositol. Serum myoinosito1 was higher in preterm than in term newborns. In healthy newborns there was a negative correlation between lung effluent phosphatidylglycerol (expressed as percent of the phospholipids) and serum myoinositol (r = - 0.968), and a positive linear correlation between myoinositol and lung effluent phosphatidylinositol (r = 0.849). In RDS at birth, undetectable phosphatidylglycerol corresponded with high serum myoinositol. During the first 5 neonatal days serum myoinositol either (1) decreased and phosphatidylglycerol appeared, (2) remained high and phosphatidylglycerol correspondingly low in some small preterm infants, or (3) decreased but phosphatidylglycerol did not expectedly increase and disaturated lecithin/ sphingomyelin ratio remained low in other small preterm babies. We propose that a premature decrease in serum myoinositol among small preterm infants with RDS is not beneficial, since myoinositol may promote hormone-induced lung maturation and healing of lung damage.

Address for correspondence: Mikko Hallman, StenbLkinkatu 11, 00290 Helsinki 29, Finland 0378-3782/85/$03.30

M.D.,

Children’s

Hospital,

Q 1985 Elsevier Science Publishers B.V. (Biomedical

University

Division)

of

Helsinki,

246

respiratory distress syndrome; lung surfactant; dylglycerol; phosphatidylinositol

myoinositol;

L/S ratio; phosphati-

Introduction

Lung effluent phospholipids reliably evaluate fetal lung maturity [l&35] and abnormalities in surfactant after birth [19,24,27]. Dipalmitoylphosphatidylcholine (PC) virtually eliminates the surface forces during expiration. Phosphatidylglycerol (PG) and phosphatidylinositol (PI) are important in maintaining the surface activity and biosynthesis of surfactant PC [2,17,32,34]. Lung effluent from immature fetus or from respiratory distress syndrome in the newborn (RDS) contains no PG, but often prominent PI. Appearance and increase in PG, is associated with decrease in PI. Animal studies revealed that the successive development of surfactant PI and PG cannot only be explained on the basis of enzyme activities directly involved in PG or PI formation [4,7,22,25]. Instead, myoinositol was found to decrease surfactant PG and to increase surfactant PI [22,4,7]. Plasma levels of myoinositol are several-fold higher in fetuses than in older individuals [10,36]. However, the concentration of this sugar in various tissues, including the lung, is high regardless of the developmental stage, and the synthesis of myoinositol from glucose 6-phosphate apparently takes place in any tissue [9,13,29,30,39]. Myoinositol is considered to be a growth factor in vitro [16]. Absence of myoinositol in diet may cause alterations in skin, liver, and intestine in animals [5,11,12]. It has been proposed that a decrease in neuronal myoinositol contributes to diabetic neuropathy [20], and that myoinositol excess is important in the pathogenesis of uremic neuropathy [14]. None of these apparently harmful effects of myoinositol deficiency or excess have been demonstrated in man. In the present study we have found a striking relationship between serum myoinositol and lung effluent phospholipids, suggesting that serum myoinositol levels influence the metabolism of lung surfactant in the newborn.

Patients and Methods

The study on myoinositol levels included 15 infants that were born by elective cesarean section without labor. Amniotic fluid, and serum from umbilical artery, umbilical vein and maternal vein were collected. The umbilical specimens were withdrawn within 15 min of .double clamping of the umbilical cord. None of these infants had RDS. Nineteen cases of RDS were studied. The diagnosis was based upon the respiratory distress that lasted for at least 3 days, typical clinical signs and radiographic findings. In addition, the phospholipids recovered from the airways at birth revealed the absence of PG and low L/S ratio [19,24]. Two patients had RDS and sepsis. The severity of RDS was evaluated as follows: in “mild” disease, the patients had no

241

mechanical ventilation. “Moderate” RDS required FiO, of < 0.45 and the mean airway pressure of < 7 cm H,O, whereas “severe” RDS required FiO, of > 0.45 and/or the mean airway pressure of > 7 cm H,O. Six other patients had severe respiratory failure without RDS. Four of these infants had sepsis, two severe asphyxia and respiratory failure. There were 22 other newborn without evidence of lung disease. Four of them had apnea, four patent ductus arteriosus, three congenital heart disease, one intestinal obstruction, three had meconium in amniotic fluid (no meconium in tracheal aspirate), and seven were healthy newborn. From intubated patients the tracheal aspirate was collected before the age of 12 h, at the age of 2 and 5 days. The aspirate was collected to a Lukens trap during routine suctioning of the airways, as described previously [24]. There were 7 infants that did not require intubation. In these cases the pharyngeal aspirate was obtained at birth. In infants with RDS, serum was obtained at the age of less than 12 h, 2, and 5 days. For the other infants a serum specimen was obtained at the same time as the specimen of lung effluent. Informed consent was obtained for each infant that was studied. The indications of mechanical ventilation were insufficient alveolar ventilation (PaCO, > 70 mmHg) or hypoxemia despite 60% oxygen. Infants were ventilated with Baby Bird ventilators (Palm Springs, CA) using long inspiratory phase permitting low peak inspiratory pressures. Arterial oxygen tension was maintained between 50 and 80 mmHg. Patent ductus arteriosus was evaluated by clinical findings of a left to right shunt, by radiographic findings of enlarged cardiothoracic ratio and pulmonary plethora, and by echocardiographic evidence of increased left atrial/aortic root ratio. When one or several of these signs were present, the patent ductus arteriosus was either treated with indomethacin, provided that there were no contraindications to its use, or closed surgically [31]. Serum myoinositol, and myoinositol from cell-free amniotic fluid were measured as described previously [28]. A known amount of a-methyl mannoside was added to each specimen. It served as an internal standard for calculation of myoinositol concentration. The freeze-dried, deproteinized sample was converted to trimethylsilyl derivatives, which were analyzed by gas chromatography equipped with an integrator. The recovery of trimethylsilyl myoinositol was variable, but this variability was compensated for a similar recovery of a-methyl mannoside. The area under the curve for trimethylsilyl myoinositol was 115 + 5% of the equimolar trimethylsilyl a-methyl mannoside. The precision between the runs expressed as the variation coefficient was 6%. The samples were run in duplicate or triplicate. Simultaneous specimens were withdrawn from the abdominal aorta and from heelstick in nine cases. Since the serum levels were not significantly different (P > 0.7, paired t-test), the subsequent specimens were either from aorta or from heelstick. The lipids were recovered using chloroform methanol extraction; the phospholipids were separated by two-dimensional thin layer chromatography, and the individual phospholipids quantified on the basis of the phosphorus content, as described previously [24]. Disaturated PC was analyzed according to Mason et al. [38,28]. The group means were compared after adjustment for gestational age (analysis of covariance, ref. 15). The correlations between serum myoinositol and tracheal

248

aspirate phospholipids were analyzed by linear, logarithmic, exponential, and power regression. The best fit is reported. The results are expressed as means f S.E.M.

Results

In 15 cases undergoing elective cesarean section, amniotic fluid and sera from umbilical artery, umbilical vein, and maternal vein were analyzed for myoinositol (Table I). Sera from umbilical artery had higher myoinositol than did those from the vein, except in four cases. Amniotic fluid myoinositol levels were lower (P < 0.05, paired r-test) than those in fetal serum. The maternal serum levels were low and did not correlate with fetal serum or amniotic fluid levels among these subjects. Fig. 1 illustrates serum myoinositol levels during the first 12 neonatal hours as a function of gestational age. Myoinositol was higher in RDS than in no-RDS, the numbers adjusted for gestational age being 0.57 + 0.07 mM for RDS, and 0.28 f 0.02 mM for no-RDS (P < lo-*). Myoinositol decreased as a function of gestational age both in infants with RDS and in those with no-RDS (P < 10e4): the rate of decrease was not significantly different between the two groups. Serum myoinositol tended to be high during sepsis or within 24 h after severe birth asphyxia (0.53 + 0.07 mM, n = 6; controls adjusted for gestational age; 0.39 + 0.03 mM, P < 0.1). In the newborn that had no pulmonary disease, there was a negative correlation TABLE I Free myoinositol in serum and in amniotic fluid a 1. 2. 3. 4.

0.20 f 0.03 mM 0.18f0.03 mM 0.14 f 0.02 mM 0.05 f 0.01 mM

Umbilical artery Umbilical vein Amniotic fluid Maternal vein

B The specimens were recovered during 15 cesarean sections without labor. None of the infants had RDS. Significant (P < 0.05) correlation between 1 and 3; 1 and 2; ‘2 and 3.

25

30 WEEKS

35

40

‘s

GESTATION

Fig. 1. The relationship between gestational age and serum myoinositol during the first 12 neonatal hours. Each circle represents one infant. Serum was obtained either from he&tick or from abdominal artery.

249

between serum myoinositol and the percentage of PG in lung effluent (Fig. 2), and a positive correlation between myoinositol and PI (Fig. 3). A similar, but not identical correlation was found between serum myoinositol and the acidic phospholipids in the amniotic fluid. There was no significant correlation between serum myoinositol and the other lung effluent phospholipids (data not shown). All these cases had high disaturated PC/sphingomyelin ratio (10.9 f 0.9). In RDS during 12 neonatal hours PG was undetectable ( < 1% of total phosphohpids), and serum myoinositol high (Fig. 1). This association corresponded with the 95% confidence limits shown in Fig. 2. In RDS during 12 neonatal hours, the percentage of PI fell above the 95% confidence belt in Fig. 3 in nine out of 17 possible cases (two cases of RDS had insufficient tracheal aspirate return for quantitative phospholipid analysis). All nine infants with “low” PI had severe RDS during the 12 neonatal hours, whereas out of the eight cases with “high” PI six had severe RDS. Out of nine cases with “low” PI at birth, three had severe RDS on the 5th day, whereas out of eight cases with “high” PI at birth two had severe RDS on the 5th day. A study of the relationship between serum myoinositol and lung effluent PG during the postnatal course of RDS revealed three different patterns: (1) In six cases (gestational age 34 * 0.9 weeks) PG appeared as expected on the basis of decreasing serum myoinositol (PG within the 95% confidence limits shown in Fig. 2). Four of these infants had severe RDS during 12 neonatal hours, and none on the 5th day. (2) In six cases (gestational age 29.3 * 1.3 weeks) PG was undetectable during the study period, and myoinositol concentration remained above 0.35 mM. All these infants had severe RDS during 12 neonatal hours, and one on the 5th day. (3) In five cases (gestational age 30.0 f 0.9 weeks) serum myoinositol decreased and PG remained low, i.e. below the confidence limits shown in Fig. 2. All these cases had severe RDS throughout the study period. Six other cases of severe respiratory failure following sepsis or asphyxia were studied for their lung effluent phospholipids and serum myoinositol at mean age of 4 ^

0.6

\

0.6

I

r = 0.849

-5

r= 0.966

0.5

oAge

cl2

h

aAge

1 to 5 days

o,4

/

_

,’ oAge A Age

~12 h 1 to 5 day;,’

,

/‘O

/ : 0

0.3-

PERCENT

PHOSPHATIDYLGLYCEROL

PERCENT

PHOSPHATIDYLINOSITOL

Fig. 2. The relationship between lung effluent phosphatidylglycerol and serum myoinositol with no RDS. The power regression line and the 95% confidence limits are shown.

among infants

Fig. 3. The relationship between lung effluent phosphatidylinositol and serum myoinositol with no RDS. The linear regression line and the 95% confidence limits are shown.

among infants

< 0.5 2 5

< 0.5 2 5

< 0.5 2 5

2 32 weeks “mild” to “ moderate”

c: 32 weeks, “moderate”

< 32 weeks, “ severe”

0.63 f 0.10 (6) 0.48 f 0.11 (6) 0.24 f 0.04 (6) d

0.76 zk0.09 (5) 0.70 +I0.16 (5) 0.59 f 0.06 (5) =

0.49 + 0.04 (6) b 0.26 + 0.04 (6) ’ 0.17 f 0.02 (6) d

Serum myoinositol tmM)

1.8kO.2 (5) 2.8 +0.2 (6)’ 3.0 f 0.3 (6) ’

2.0 rt 0.2 (4) 4.0 f 0.4 (5) c,e 5.9 f0.5 (5) d,e

2.3kO.2 (6) 5.2f0.5 (6)’ 4.9 f 0.7 (3) c

Disaturated phosphatidylcholine/ sphingomyetin

0.46 * 0.02 0.47 f 0.03 0.42 f 0.02

0.48 f 0.07 0.48 + 0.04 0.52 + 0.03

0.47 i 0.06 0.58 + 0.03 0.55 +0.03

Disaturated phosphatidylchol~ne/ phosphatidylcholine

4b total phosphohpids

7.5rt0.8 8.6 + 0.6 6.3+ 1.0

8.0& 1.0 11.9+1.0d 13.1 kO.8 d

9.6 f 0.8 10.9 * 0.9 10.3f0.8

Phosphatidylinositol

0.2kO.2 0.2 +0.2 0.9 + 0.4

0.3 f 0.2 O.OkO.3 0.6 + 0.3

0.3 kO.2 2.4 + 0.2 ’ 2.5 + 0.3 c

Phosphatidy~gtycerol

a “M&i” RDS is hereby defined as disease that no more required respirator treatment on day 5; “moderate” RDS required FiO, < 0.45 and mean airway pressures < 7 cm H,O on day 5; “severe” RDS required FiOz > 0.45 and/or mean airway pressures > 7 cm H,O on day 5. ’ Number of infants. ’ Significantly different than on day 0 (P -C0.025). d Significantly different than on day 0 and day 2. (P < &025). ’ Significantly higher than in “severe” RDS (P <: 0.0125).

Days after birth

Gestational age and severity a

Serum myoinositol and the phospholipids of lung effluent during the course of RDS

TABLE II

251

days. They were as follows: disaturated PC/sphingomyelin 3.0 k 0.4; % disaturated over total PC 0.38 * 0.02; % PI 3.1 f 0.1; % PG 2.0 + 0.3; and serum myoinositol 0.12 &-0.01 mM. These figures were similar to those in group (3) RDS after the birth (data not shown). In each case PG fell below the confidence limits shown in Fig. 2. Therefore, group (3) RDS cases and the six cases of severe respiratory failure, following sepsis or asphyxia, were analyzed together. The correlation between serum myoinositol and W PG (myoinositol 0.15 f 0.02 mM; PG 1.7 f 0.2%, power regression, r = - 0.582) was significantly lower (P < 0.02) than the corresponding correlation among the newborn with no lung disease. One explanation for the loss of correlation between myoinositol and PG, is lack of surfactant and/or excess non-surfactant phospholipids in lung effluent. In order to evaluate this possibility we recalculated PG as 5%of surfactant phospholipid instead of as % of total lung effluent phospholipid. It was assumed that 55% of surfactant phospholipids consists of disaturated PC and that PG and disaturated PC are only present in surfactant [41]. On the basis of this assumption, only a mean of 50% of the lung effluent phospholipids represented surfactant. PG represented 3.3 + 0.3% of surfactant phospholipids, and there was a good negative correlation between myoinositol and PG (power regression, r = -0.831; correlation significantly better than the previous one, r = between serum myoinositol and - 0.582, P < 0.05). Therefore, the poor correlation lung effluent PG among these cases of severe respiratory failure may in part be explained on the basis of paucity of surfactant in lung effluent. Table II shows serum myoinositol and lung effluent phospholipids in RDS. Two infants with RDS and sepsis were excluded from the study. The cases were divided into three categories on the basis of gestational age and severity of respiratory failure. In RDS among infants born at 32 weeks of gestation or later, the postnatal fall in serum myoinositol was associated with increase in PG. However, among more immature infants with RDS, PG remained undetectable or low at least for 5 days. This was apparently due to surfactant deficiency (“severe” RDS), or due to high myoinositol (“moderate” RDS).

Discussion The present results, together with previous experimental data, demonstrate evidence on a striking negative correlation between serum myoinositol and surfactant PG in healthy newborn babies. There was also a positive correlation between serum myoinositol and lung effluent PI. These findings support the concept that serum myoinositol levels reflect the availability of myoinositol for surfactant PI synthesis in type II cells. However, extracellular myoinositol may have little effect on most other cells with high myoinositol content [4,7,22]. Myoinositol stimulates surfactant PI synthesis by providing a substrate for enzyme, CDP-diacylglycerol : inositol phosphotransferase, and thus depleting another rate limiting substrate, CDP-diacylglycerol, from PG. This appears to be the basis of the observed negative correlation between serum myoinositol and surfactant PG and the positive correlation between myoinositol and PI [22].

252

According to present evidence a decrease in serum myoinositol decreases the inhibition of PG synthesis, allowing an increase in PG and concomitant decrease in PI. This phenomenon was evident in healthy newborn and during recovery from RDS among the newborn with gestational age of more than 32 weeks (Table II). According to Beppu et al. [6], the myoinositol-induced modification in the quality of the acidic surfactant phospholipids in adults does not alter the surface activity of surfactant. Therefore, the physiological significance of the decline in serum myoinositol and the resulting increase in PG remains unclear. Factors that possibly influence serum myoinositol concentrations during the perinatal period include biosynthesis from glucose 6-phosphate [9], release from the cells, especially the liver [9,40], uptake into the tissues [g], myoinositol in the diet [26], rate of oxidation of myoinositol into glucuronic acid in the kidney [26], secretion of myoinositol into urine [36], recycling of amniotic fluid myoinositol, or loss of amniotic fluid myoinositol through ruptured fetal membranes. The importance of these potential regulatory steps remains to be established. In the present study infants with respiratory distress had a low myoinositol intake. Despite this, some tiny infants with RDS maintained high myoinositol levels during the study period of 5 days, whereas, in most cases, myoinositol decreased. Although there was a striking negative correlation between serum myoinositol and lung effluent PG at birth, this correlation was less evident among some infants with severe respiratory failure. This cannot only be explained on the basis of the time period of about 1 day that is required for newly synthesized surfactant to appear in tracheal aspirate [33]. The present evidence suggests that the less striking correlation between myoinositol and PG in part was due to prominence of nonsurfactant phospholipids and/or deficiency of surfactant phospholipids in lung effluent. Similar abnormalities in bronchoalveolar lavage phospholipids in the presence of low serum myoinositol have been found in adult respiratory distress syndrome [27]. Furthermore, in the experimental lung damage, the alveolar lavage phospholipids appear similar to those in infants and adults with severe respiratory failure and with low serum myoinositol [23]. These abnormalities that included a decrease in surfactant phospholipids and an increase in alveolar non-surfactant phospholipids [37], were relieved by dietary myoinositol that increased the serum levels to equal or higher than those present among immature fetuses [23]. It has been demonstrated that high myoinositol augments the glucocorticoid-induced increase in the synthesis and secretion of disaturated surfactant PC in immature rabbit lung [21]. The results of the present study are in accordance with these findings. Lowering of serum myoinositol among small premature infants with RDS had no demonstrable benefits. Instead, infants with lowered serum myoinositol tended to have more severe RDS (including lower disaturated PC/sphingomyelin ratio and PI) than those infants who maintained the high serum myoinositol during the first neonatal days. On the basis of these findings we propose that high serum myoinositol promotes the hormone-induced acceleration of lung maturation that may take place for instance in RDS during the first neonatal days [l]. This hypothesis remains to be tested further.

253

Acknowledgements Supported by NIH grant HD 04380 (L.G.), Foundation (M.H.).

Finnish

Academy

and Sigrid Juselius

References 1 Baden, M., Bauer, C.B., Colle, E.. Klein, G., Taeusch, H.W. and Stem, L. (1972): A controlled trial of hydrocortisone therapy in infants with respiratory distress syndrome. Pediatrics, 50, 526-534. 2 Bangham. A.D., Morley, C.J. and Phillips, M.C. (1979): The physical properties of an effective lung surfactant. B&him. Biophys. Acta, 573, 552-556. 3 Barrett, C.R., Bell, A.L.L. and Ryan, SF. (1979): Alveolar epithelial injury causing respiratory distress in dogs. Chest, 75, 705-711. 4 Batenburg, J.J., Klazinga, W. and Van Golde, L.M.G. (1982): Regulation of phosphatidylglycerol and phosphatidylinositol synthesis in alveolar type 11 cells isolated from adult rat lung. FEBS Lett.. 147, 171-174. 5 Beach, D.C. and Flick, P.K. (1982): Early effect of myoinositol deficiency on fatty acid synthetic enzymes of rat liver. Biochim. Biophys. Acta, 711, 452-459. lung surfactant has 6 Beppu, OS., Clements, J.A. and Goerke, J. (1983): Phosphatidylglycerol-deficient normal properties. J. Appl. Physiol.: Resp. Environ. Exercise Physiol., 55. 4966502. on 14C glycerol I Bleasdale, J.E., Busch, F.N. and Quirk, J.G. (1982): The effect of myoinositol incorporation into glycerophospholipids by rat type II pneumocytes. Am. Rev. Respir. Dis.. 125. 193. 8 Bleasdale. J.E., Maberry, M.C. and Quirk, J.G. (1982): Myoinositol homeostatis in fetal rabbit lung. Biochem. J., 206, 43-52. 9 Burton, L.E. and Wells, W.W. (1974): Studies on the developmental pattern of the enzymes converting glucose 6-phosphatase to myoinositol in the rat. Dev. Biol., 37, 35-42. 10 Campling, J.D. and Nixon, D.A. (1954): The inositol content of foetal fluids. J. Physiol.. 126. 71-80. 11 Chu. S.-H.W. and Hegsted, D.M. (1980): Myoinositol deficiency in gerbils: changes in phospholipid composition in intestinal microsomes. J. Nutr., 110, 1217-1223. 12 Cunha. T.J. (1971): Inositols: deficiency effects in animals. In: The Vitamins: Chemistry, Physiology, Pathology, Vol. III, pp. 394-398. Editors: W.H. Sebrell and R.S. Harris. Academic Press, New York. of free mesoinositol in mammalian tissues, 13 Dawson, R.M.C. and Freinkel, N. (1961): The distribution including some observations on the lactating rat. B&hem. J.. 78, 606-610. 14 De Jesus, P.V. Jr., Clements, R.S. Jr. and Winegrad, A.I. (1974): Hypermyoinositolemic polyneuropathy in rats: a possible mechanism for uremic neuropathy. J. Neurol. Sci., 21, 237-249. 15 Dixon, W.J. (1981): BMDP Statistical Software. University of California Press, Berkeley. CA. 16 Eagle, H., Oyama, V.I., Levy, M. and Freeman, A.E. (1957): Myo-inositol as an essential growth factor for normal and malignant human cells in tissue culture. J. Biol. Chem.. 226, 191-205. 17 Feldman, D.A., Kovac, C.R., Dranginis, P.A. and Weinhold. P.A. (1978): The role of phosphatidylglycerol in the activation of CTP: phosphocholine cytidylyltransferase from rat lung. J. Biol. Chem., 253. 4980-4986. 18 Cluck, L., Kulovich, M.V., Borer, R.C., Brenner, P.H., Anderson, G.G. and Spellacy, W.N. (1971): Diagnosis of the respiratory distress syndrome by amniocentesis. Am. J. Obstet. Gynecol.. 109. M-445. 19 Cluck, L.. Kulovich, M.V., Eidelman, H.I., Cordero, L. and Khazin, A.F. (1972): Biochemical development of surface activity in mammalian lung. IV. Pulmonary lecithin synthesis in the human fetus and newborn and etiology of the respiratory distress syndrome. Pediat. Res., 6, 81-99. 20 Greene, D.A., De Jesus, P.V. Jr. and Winegrad, A.I. (1975): Effects of insulin and dietary myoinositol on impaired peripheral motor nerve conduction velocity in acute streptozotocin diabetes. J. Clin. Invest.. 55, 1326-3336. 21 Hallman, M. (1984): Effect of extracellular myoinositol with surfactant phospholipid synthesis in the fetal rabbit lung. B&him. Biophys. Acta (in press).

254

22 Hallman, M. and Epstein, B.L. (1980): Role of myoinositol in the synthesis of phosphatidylglycerol and phosphatidylinositol in the lung. B&hem. Biophys. Res. Commun., 92, 1151-1159. 23 Hallman, M. and Epstein, B.L. (1982): Myoinositol lung surfactant deficiency. Life Sci., 31, 175-180.

decreases

N-nitroso-N-methylurethane

induced

24 Hallman, M., Feldman, B.H., Kirkpatrick, E. and Gluck, L. (1977): Absence of phosphatidylglycerol (PG) in respiratory distress syndrome in the newborn. Study of the minor surfactant phospholipids newborns. Pediat. Res., 11, 714-720.

in

25 Hallman, M. and Gluck, L. (1980): Biosynthesis of acidic surfactant phospholipids during perinatal period in the rabbit. Pediat. Res., 14, 1250-1259. 26 Hallman, M., Slivka, S., Epstein, B.L., Johnson, S., Benirschke, K. and Gluck, L. (1983): Role of fetal myoinositol oxygenase and of maternal myoinositol intake in regulation of fetal serum myoinositol. Clin. Res., 31, 134. 27 Hallman, M., Spragg, R., Harrell, J.H., Moser, K.K. and Gluck, L. (1982): Evidence of lung surfactant abnormality in respiratory failure. Study of bronchoalveolar lavage phospholipids, surface activity, phospholipase activity, and plasma myoinositol. J. Clin. Invest., 70, 673-683. 28 Hallman, M., Wermer, D., Epstein, B.L. and Gluck, L. (1982): Effects of maternal insulin or glucose infusion on the fetus: study on lung surfactant phospholipids, plasma myoinositol, and fetal growth in the rabbit. Am. J. Obstet. Gynecol., 142, 877-882. 29 Hauser, G. and Finelli, I.N. (1963): The biosynthesis of free and phosphatide myo-inositol from glucose from mammalian tissue slices. J. Biol. Chem., 238, 3224-3228. 30 Hokin, M.R. and Hokin, L.E. (1953): Enzyme secretion and the incorporation of P” into phospholipids of pancreats slices. J. Biol. Chem., 203, 976-977. 31 Jacob, J., Gluck, L., DiSessa, T., Edwards, D., Kulovich, M., Kurlinski, J., Merritt, T.A. and Friedman, W.F. (1980): The contribution of PDA in the neonate with severe RDS. J. Pediat., 96, 79-87. 32 Jacob, J., Hallman, M. and Gluck, L. (1980): The effect of phosphatidylglycerol and phosphatidylinositol on dipalmitoyl lecithin monolayer. Pediat. Res., 14, 644. 33 Jobe, A., Mannino, F. and Gluck, L. (1978): Labeling of phosphatidylcholine in the alveolar wash of rabbits in utero. Am. J. Obstet. Gynecol., 132, 53-58. 34 King, R.J. (1982): Pulmonary surfactant, J. Appl. Physiol.: Respir. Environ. Exercise Physiol., 53, 1-9. 35 Kulovich, M.V., Hallman, M. and Gluck, L. (1979): The lung profile I. - Normal pregnancy. Am. J. Obstet. Gynecol., 135, 57-63. 36 Lewin, L.M., Melmed, S., Passwell, J.H., Yannai, Y., Brish, M., Orda, S., Boichis, (1978): Myoinositol in human neonates: serum concentrations and renal handling.

H. and Bank, H. Pediat. Res., 12,

3-8. 37 Liau, D.F., Barrett, R.C., Bell, A.L.L. and Ryan, S.F. (1981): Surfactant phosphatidylglycerol in experimental acute alveolar injury in the dog. Am. Rev. Respir. Dis., 123, 98. 38 Mason, R.J., Nellenbogen, J. and Clements, J.A. (1976): Isolation of disaturated phosphatidylcholine with osmium tetroxide. J. Lipid Res., 17, 281-284. 39 Michell, R.H. (1975): Inositol phospholipids and cell surface receptor function. B&him. Biophys. Acta, 415, 81-147. 40 Nixon, D.A. (1968): The concentration of free myo-inositol Biol. Neonate, 12, 113-120. 41 Van Golde, L.M.G. (1976): Metabolism of phospholipids 977-1000.

in the plasma

of perfused

sheep foetuses.

in the lung. Am. Rev. Respir.

Dis., 114,