AJP - Lung Cellular and Molecular Physiology, Vol 259, Issue 4 238-L246, Copyright © 1990 by American Physiological Society
Uptake of instilled radiolabeled lamellar bodies from alveolar compartment of the rat
T. E. Nicholas, H. A. Barr, J. H. Power and M. E. Jones
Department of Human Physiology, School of Medicine, Flinders University of South Australia, Adelaide.
Following the instillation of lamellar bodies containing dipalmitoyl
phosphatidyl-[3H]choline (DPPC) down the trachea of adult rats, we found
that the half-life of alveolar [3H]-DPPC was 85 min and the time constant
was 120 min. As much as 85% was recycled. When we labeled the DPPC with
both [3H]choline and [14C]acetate, the ratio 3H/14C increased in the
alveolar compartment and then increased further in the lamellar body
fraction of the recipient lungs, suggesting that some
deacylation-reacylation was occurring. Further evidence of degradation was
an increase in free [3H]choline in the microsomal fraction. Whereas
hyperpnea induced by breathing 5% CO2-13% O2-82% N2 increased the reuptake
of DPPC, reuptake did not appear to be enhanced in the rest period
immediately after hyperpnea induced by swimming, when alveolar DPPC was
still markedly elevated. Propranolol did not affect reuptake, suggesting
that beta-adrenoreceptors were not essential. We suggest that reuptake is
coupled more to release than to the amount of surfactant in the alveolar
compartment.
