1987 Volume 18 Issue 2 Pages 185-194
Pulmonary tissues obtained from 12 individuals suffering from congenital heart disease accompanied with Down syndrome were examined by light and transmission electron microscopy and compared with those of 29 cases without the syndrome. Alkaline phosphatase (ALPase) activity was histochemically examined and compared as well. Ultrastructural changes found in the pulmonary tissues examined from the patients with pulmonary hypertension were as follows: 1) infolded and twisted basement membrane along the abluminal surface of the capillary, 2) a thickened capillary wall composed of the endothelial cell cytoplasm, 3) accumulation of collagenous fibrils within the enlarged pericapillary interstitial space, 4) increase in the number of type II alveolar cells. These changes were more conspicuous and encountered more frequently in the pulmonary hypertensive individuals with Down syndrome than in those without the syndrome. Furthermore, they were detected at an earlier age in the patients with Down syndrome. ALPase activity, which is known to be important in the secretion of pulmonary surfactant, was detected in the plasma membrane of type II alveolar cells and in the limiting membrane of the osmiophilic bodies. Activity was more intense in the pulmonary tissues obtained from the patients suffering from pulmonary hypertension than in those from the patients without the hypertension, irrespective of Down syndrome. These observations may indicate that the alveolar tissue including the type II alveolar cells and the capillary endothelium are affected at an earlier stage in the patients with Down syndrome. The increase in ALPase activity as stated above seems to correlate with changes in the structure of the type II alveolar cell and also with the secretion of the pulmonary surfactant.
