AJP - Lung Cellular and Molecular Physiology, Vol 267, Issue 5 585-L591, Copyright © 1994 by American Physiological Society
Maturation-related changes in endothelial nitric oxide synthase immunolocalization in developing ovine lung
A. C. Halbower, R. M. Tuder, W. A. Franklin, J. S. Pollock, U. Forstermann and S. H. Abman
Department of Pediatrics, University of Colorado School of Medicine, Denver 80262.
It is unknown whether high fetal pulmonary vascular tone is due in part to
absent or decreased endothelial nitric oxide synthase (eNOS), the enzyme
that produces nitric oxide in the vascular endothelium. To determine the
timing of appearance and maturational changes of eNOS in the developing
pulmonary circulation, we performed immunohistochemistry in lungs from
fetal, neonatal, and adult sheep. Using a mouse monoclonal antibody against
bovine aortic eNOS, we found immunoreactive eNOS selectively in the
endothelium and it was present at all fetal ages. Immunoreactivity was seen
as early as 29% gestation in the developing capillaries coursing through
fetal mesenchyme. By 6 days after birth, immunoreactivity was decreased in
most vessels and nearly absent in the distal pulmonary arteries of adult
animals. We conclude that immunoreactive eNOS is present very early in
fetal life and appears to decrease postnatally. We speculate that the early
presence of eNOS in the fetal lung supports a possible role for endogenous
nitric oxide activity in the regulation of vascular tone or angiogenesis in
the developing pulmonary circulation.
