Hans Johnsson

Lung Hyaluronan and Water Content in Preterm and Term Rabbit Pups Exposed to Oxygen or Air

Rabbit pups were delivered by cesarean section 1 or 2 d before term, or vaginally around term, and then reared in room air or exposed to intermittent or continuous hyperoxia (>85%) for up to 9 d. Pups were killed at different ages, and lung hyaluronan (HA; µg/g of dry lung weight) and lung water content, measured as wet/dry lung weight, were determined. Compared with the day of birth, the lung HA concentration did not change significantly on succeeding days in pups kept in air delivered 2 d (-2 d) or 1 d (-1 d) before term, whereas the water content decreased significantly. Continuous exposure to hyperoxia resulted in a significantly raised lung HA concentration 6 d postterm in both -2 d and -1 d pups, and intermittent exposure to hyperoxia resulted in a significantly raised HA concentration 6 d postterm in -1 d pups, compared with the groups exposed to room air. These increases were accompanied by significantly elevated wet/dry lung weight ratios. Microscopic examination revealed significantly increased HA staining scores in alveoli, arterioles, and bronchioli in both hyperoxia-exposed groups of -2 d pups 6 d postterm, and nonsignificantly higher scores in -1 d and vaginally delivered pups of comparable age, compared with the scores at birth. The results indicate that oxygen exposure neonatally may result in an increase in lung HA accompanied by an increase in lung water content. The increase in lung HA concentration in our study may be an affect of oxygen free radicals or oxygen-induced stimulation of inflammatory mediators.

205 HYALURONAN AND WATER CONTENT IN THE LUNG OF PRETERM AND TERM INFANTS WHO DIED LESS THAN 24 HOURS AFTER BIRTH

Fetal connective tissue is known to have a very high concentration of hyaluronan (HA) and of water. In rabbit pups the concentration of HA in the lung has its lowest value one day before term gestation (Am J Physiol 260, 1449, 1991). After birth an increase in lung HA is accompanied by an increase in lung water (Ped Res 1992;32: 635& 1994;35:280).AIM: To determine the concentration of HA and water in the lung of infants who died less than 24 hours after birth.RESULTS: The HA concentration in the lungs of infants born after 23-27 gestational weeks (g.w.)ranged between 1030-2832 μg/g dry lung weight(n=8) and in those born after 2 28 g.w. between 374-1875 μg/g(n=21). The relation between HA concentration and gestational age seemed exponential. Lung water content was high in all infants. HA staining in lung structures was more widely spread in very preterm than in more mature infants. A subepithelial lining of HA could be seen in moderately preterm infants.CONCLUSION: The concentration of hyaluronan in the lungs of newborn infants decreased with increasing gestational age at births. The water content of thp lungs of all infants in this study was high.

Antenatal betamethasone administration decreases the lung hyaluronan concentration in preterm rabbit pups.

Maternal treatment with corticosteroids before preterm delivery is effective in reducing the incidence of respiratory distress syndrome and neonatal mortality. We hypothesized that corticosteroids might lower the lung hyaluronan concentration. Twenty-five rabbit dams (term = 31 d) with timed pregnancies were injected s.c. with 0.75 mg of betamethasone or saline (controls) 1 d before delivery. In addition, two dams delivered at 25 d of gestation were injected with 0.75 mg of betamethasone on two consecutive days before delivery. A total of 238 live pups were delivered by preterm cesarean section at 25, 27, 28, or 29 d of gestation and killed immediately. Their lung hyaluronan concentrations were measured with a radiometric assay, and wet/dry lung weight ratios were determined. Lungs of rabbit pups exposed antenatally to betamethasone and delivered at 25 or 27 d of gestation, but not at 28 or 29 d, displayed significantly (p = 0.001 and p = 0.008, respectively) lower hyaluronan concentrations than control pups, accompanied by less intense subepithelial staining for hyaluronan in alveolar walls. There was no significant difference in wet/dry lung weight ratio between pups exposed to one dose of betamethasone and controls. Antenatal corticosteroid exposure lowers the lung hyaluronan concentration in preterm rabbit pups delivered at 25 or 27 d of gestation, but not in those delivered at 28 or 29 d.

HYALURONAN AND WATER CONTENT IN THE LUNGS OF TERM RABBIT PUPS KEPT IN AIR OR OXYGEN

Increased lung water is considered to be an important component in neonatal respiratory distress. In adult respiratory distress increased lung water is accompanied by high levels of hyaluronan concentrations in broncho-alveolar lavage fluid (Am Rev Resp Dis 1989;139:682-87). Little is known about lung hyaluronan content in the perinatal period. In rabbit pups lung hyaluronan concentration decreases just before term and lung water decreases at term (Am J Physiol 1991;260:H1449-54). Data on preterm rabbits have been presented previously (Ped Res 1992;32;635. The present study was undertaken to study the effect of oxygen exposure on lung hyaluronan concentration and lung water in rabbit pups born at term. Some pups were kept in oxygen and some were kept in air. Pups were sacrificed and lungs were taken at an age of 4-6 days. The water content was measured as wet/dry weight, and the hyaluronan concentration with a radiometric assay kit (HA 50, Pharmacia, Uppsala).Results: In the lungs from pups kept in oxygen significantly higher hyaluronan concentrations were seen both at 4 (p<0.001;n = 14) and 6 (p<0.01;n = 17) days of age compared to the lungs from the pups kept in air (n = 15 and 29, respectively). This was accompanied by a higher lung water content (p<0.001) than in pups kept in air at 4 days of age.Conclusion: In term rabbit pups lung hyaluronan concentration and lung water content increase during oxygen exposure.

Hyaluronan in the Human Neonatal Lung: Association with Gestational Age and Other Perinatal Factors

The aim of this study was to determine the influence of gestational age at birth, postnatal age, specific complications and methods of treatment on the lung hyaluronan concentration in infants. Lung samples and clinical records from 117 infants who died 0–228 days (32 weeks) after preterm or term birth were studied. The lung hyaluronan concentration at death was most strongly associated with the gestational age at birth, an association best described by an exponential function with a negative power coefficient. After adjustments for gestational age, the lung hyaluronan concentration also correlated significantly with birth weight, weight at death, the wet-to-dry lung weight ratio and specific staining for hyaluronan in the pleura. Intrauterine infection was also associated with a significantly higher lung hyaluronan concentration.

HYALURONAN AND WATER CONTENT IN LUNGS FROM RABBIT PUPS BORN PRETERH AND SUBSEQUENTLY KEPT IN AIR OR OXYGEN

Adult respiratory distress syndrome is associated with increased lung hyaluronan and water content (Am Rev Resp Dis 1989;139:682-87). As increased lung water also can cause neonatal disturbances, the present study was undertaken to study the effects of oxygen on lung hyaluronan and lung water in preterm rabbit pups. Some pups were kept in oxygen while controls were kept in air. Pups were sacrificed and lungs were taken at ages 2-7 days after birth. The water content was measured as wet/dry weight, and hyaluronan with HA 50 (Pharmacia).Results: In pups breathing air lung water content decreased (p<0.001) during the first day after birth and then remained at a low level. In pups born 1(a) and 2(b) days before term and breathing oxygen, higher hyaluronan levels were seen at 7(a:n=7, p<0.1) and 6(b:n-=5, p<0.001) days after birth, than in control pups breathing air (a:n=7, b:n=7). The higher content of hyaluronan was accompanied by a higher (a:p<0.05, b:p<0.01) water content than in controls.Conclusion: Lung hyaluronan and lung water increase in preterm rabbit pups during oxygen exposure.

172 WATER AND HYALURONAN CONTENT IN THE LUNGS IN THE PERINATAL PERIOD – an experimental study in rabbits

Little is known about the role of hyaluronan in perinatal lung water balance. After birth interstitial lung water gradually decreases. Later, an increase may occur due to functional disturbancies or inflammatory processes. The aim of the present study was to elucidate the changes in water and hyaluronan content in the lungs after preterm birth. Lungs were taken for analysis from rabbit pups born one or two days before term at different postnatal ages. In both gestational age groups, water content measured as wet/dry weight quotient decreased during the first day of life from 9/1 to 6-7/1, and then remained at that level during the next four days. In pups born 1 day before term hyaluronan content measured by a radiometric method as ug/g dry weight averaged 206 at birth, increased to a peak of 382 at 3 days of age (p<0.02), and then decreased again. In pups born 2 days before term the hyaluronan content reached a peak at 4 days of age. Conclusion; The immediate postnatal decrease in lung water content in healthy preterm rabbit pups is not accompanied by an over-all decrease in pulmonary hyaluronan.

Antenatal terbutaline administration decreases the lung hyaluronan concentration in preterm rabbit pups.

Objectiv: To determine whether antenatal exposure to terbutaline alters the lung hyaluronan concentration or lung water content at birth in preterm rabbit pups. Study Design: Rabbit dams (n = 18) with timed pregnancies were injected with 30 µg terbutaline or saline (controls) one day before delivery at 27–29 days of gestation. Pups were killed immediately after delivery. Lung water content and hyaluronan concentrations were determined. Results: Pups exposed antenatally to terbutaline had lower mean lung hyaluronan concentrations than control pups. Lung hyaluronan/dry lung weight was significantly lower in pups delivered at 28 (p = 0.034) or 29 days (p < 0.001), while lung hyaluronan/wet lung weight was significantly lower at all three gestational ages. Conclusion: Antenatal exposure to terbutaline lowers the lung hyaluronan concentration at birth in preterm (27–29 days) rabbit pups without altering the lung water content.

Antenatal corticosteroids lowers the hyaluronan concentration in the lungs of preterm rabbit pups

Antenatal corticosteroids lowers the hyaluronan concentration in the lungs of preterm rabbit pups

102 SURFACTANT AND N-ACETYLCYSTEINE STIMULATE THE HYALURONAN SYNTHESIS BY HUMAN FETAL LUNG FIBROBLASTS

Lung hyaluronan (HA) concentration has been found to increase in rabbit pups treated with oxygen (Ped Res 1992;32: 635 & 1994;35:280), and in premature monkeys with respiratory distress syndrome (RDS) (Ped Res 1994;35:238-43). The mechanism behind this increase is unknown.AIM: To determine if surfactant and N-acetylcysteine, used in the treatment of RDS, influence the HA synthesis by lung fibroblasts.METHOD: Human fetal lung fibroblasts (ECACC WI-38, 30,000 cells/well), were cultivated in Exosurf (colphoscerile palmitate) 1.69-54 mg/ml, Curosurf (porcine surfactant) 10-80 mg/ml, or N-acetylcysteine 5-100 mg/ml for 48 hours. Subsequently, the HA concentration of the supernatant was determined, and calculated as % of the HA concentration obtained with 10% fetal calf serum, i.e. 467±85 ng/ml ( = 100%). RESULT: With Exosurf and Curosurf HA concentrations of 127-154% and 102-132%, respectively, were obtained. HA concentrations increased from 0.2%±0.6 to 101%±44 with increased concentrations of N-acetylcysteine.CONCLUSION: Surfactant and N-acetylcysteine stimulate HA synthesis by human fetal lung fibroblasts.