Am. J. Respir. Cell Mol. Biol., Vol 13, No. 1, 07 1995, 99-108.
Elemental composition of lamellar bodies from fetal and adult human lung
MR Chinoy, LW Gonzales, PL Ballard, AB Fisher and RG Eckenhoff
Institute for Environmental Medicine, University of Pennsylvania, Philadelphia, USA.
Previous studies in the rat using electron probe microanalysis have
suggested that most of the Ca2+ in alveolar space is probably derived from
secreted lamellar bodies (LB). However, the LB Ca2+ content in cultured rat
type II cells is low and unaltered by dexamethasone supplementation. In
this study, we examined LB Ca2+ content in adult human lung and cultured
explants of fetal lung treated with hormones to promote type II cell
differentiation. Lung tissue of 20 to 24 wk of gestation was cultured for 4
to 6 days without hormone and with dexamethasone (10 nM), triiodothyronine
(2 nM), 8-bromo-cyclic adenosine monophosphate (0.1 mM), or their
combinations. The cultured tissue samples were processed for light and
electron microscopy or rapidly frozen and stored in freon-22 under liquid
nitrogen. Thin cryosections from the frozen samples were prepared and
examined using the electron probe microanalysis. Human lung tissue up to 24
wk of gestational age had no detectable LB before explant culture. Explants
cultured for 4 days without hormone supplementation (control) had no
detectable LB, single-hormone treatments resulted in small LB, and
combination treatments resulted in the formation of many large LB in
explant type II cells. Despite such morphologic changes, LB Ca2+ in both
control and hormone-treated explants was low (overall mean, 4.1 +/- 0.6; P
< 0.05) compared with LB of in situ rat and adult human lung (30 +/- 2
and 27 +/- 1.5 mmol/kg dry wt, respectively) and was similar to that found
in cultured rat type II cells. LB phosphorus and sulfur under all explant
culture conditions were comparable. These observations indicate that human
and rat LB elemental compositions are similar and that optimal in vitro
conditions with respect to LB Ca2+ metabolism have not been established.
