BOVINE FETAL LUNG DEVELOPMENT

BOVINE FETAL LUNG DEVELOPMENT

Abstract:

Fetal lung tissue obtained from abattoirs was examined histochemically using alpha-napthyl butyrate (nonspecific method), to defect the presence of pulmonary alveolar macrophages (PAM). Esterasepositive alveolar macrophages, which appear in the alveolar septa and lumina were first seen at 240 days of gestation. These macrophages were identified by the presence of numerous diffuse intensely red-stained granules in the cytoplasm. Macrophages at 240 days were 15.88 ± 1.67 Urn (S.E.) (N=30) in size and in most cells the esterase-positive granules were sparsely distributed in the cytoplasm. Only four out of eight lungs examined at 240 days were positive for alveolar macrophages. However, all the lungs (N=10) examined from 250=day-old fetuses contained esterase-positive macrophages, which were distributed both in the alveolar septa and alveolar spaces. Compared to macrophages of the 240-day fetuses, those at 250 days were signi ficantly larger, 16.91 ± 1.33 μm (S.E.) (N=30) (P<0.05). Type II pneumocytes and T lymphocytes were not confused with PAM because in all lungs, T lymphocytes contained a single, small, esterase-positive granule compared with the numerous diffuse esterase-positive granules in PAM while type II pneumocytes reacted negatively to nonspecific esterase stain during lung development. The time of appearance of alveolar macrophages coincides with the first appearance of surfactant at the alveolar surface-lining layer which suggests that macrophages could be involved with the clearing of excess surfactant being produced.

BOVINE FETAL LUNG DEVELOPMENT

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