AJP - Lung Cellular and Molecular Physiology, Vol 268, Issue 2 336-L346, Copyright © 1995 by American Physiological Society
Turnover of extracellular matrix by type II pulmonary epithelial cells
S. E. Dunsmore and D. E. Rannels
Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey 17033.
Rat type II pulmonary epithelial cells synthesize and assemble a
multicomponent extracellular matrix (ECM) which can modulate cellular
differentiation in primary culture. This study defines turnover of the type
II cell matrix. Turnover kinetics were analyzed in two types of pulse-chase
protocols based on loss of radioactive ECM components. To estimate turnover
of previously synthesized ECM, type II cells were plated on extracted
matrix that was radiolabeled 2, 3, or 6 days; alternatively, ECM was
radiolabeled in pulse-chase experiments to measure turnover by the same
cells that synthesized the matrix. Rapid initial rates of ECM turnover were
evident in both cases. While overall matrix stability appeared to change
with culture time, sodium dodecyl sulfate-polyacrylamide gel
electrophoresis analysis showed a similar spectrum of proteins in the ECM
over the course of kinetic studies. The results reveal rapid turnover of
ECM by type II cells and suggest that matrix stability may be regulated.
These observations provide a basis for future investigations of the
physiological significance of turnover of individual ECM components by the
alveolar epithelium.
