Differential effect of sex in experimental hyaline membrane disease in newborn monkeys.

Data from forty-four infant monkeys of 135 to 150 days' gestation were reviewed for the existence of sex-related differences in the development of hyaline membrane disease, post-mortem lung mechanics, biochemistry, and histologic features. Severity of hyaline membrane disease was scored from 1 (severe) to 6 (none) from chest radiographic appearance and arterial PO2 determination. Female monkeys had a lower score (mean +/- 1 SD = 2.7 +/- 1.6) than males (3.8 +/- 1.6, less than 0.05). Females accounted for 70% of animals with scores of 1 or 2, and 33% of those with scores of 5 or 6 (p = 0.045). There was no difference in lung homogenate phospholipid (PL) concentration. Airway lavage PL and the ratio of lavage PL to homogenate PL were both decreased in the female. Surface activity of the lavage material was also less in the female. No significant differences between males and females were noted for mean maximal lung volume air-tissue ratio, as determined by light microscopy, or number of type II pneumocytes per alveolus. Premature female monkeys appeared to sustain a disadvantage in pulmonary adaptation to postnatal life.