Effects of hydrogen and bicarbonate ions on endocrine cells in
fetal rat lung organ cultures.
Ebina, Masahito, Richard F. Hoyt, Nancy A. F. McNelly, Sergei P.
Sorokin, and R. Ilona Linnoila.
Laboratory of Pulmonary Cell Biology1, Department of Anatomy and
Neurobiology, Boston University School of Medicine, Boston,
Massachusetts 02118 USA, Biomarkers and Prevention Research Branch2,
Division of Clinical Sciences, National Cancer Institute, NIH,
Rockville, Maryland 20850 USA
APStracts 3:0171L, 1996.
Concentrations of H+ and HCO3- rise in fluid lining hypercapnic
airways. Effects of these ions on pulmonary endocrine cells were
studied in 119 fetal rat lung organ cultures by semiquantitative
staining for Calcitonin Gene-Related Peptide (CGRP)-like
immunoreactive material. Intracellular CGRP was determined in
cultures under "no-release" baseline conditions and
following incubation in control or test media. After exposure to
bicarbonate-free medium at pH 7.4 (incubation control), CGRP fell
moderately from no-release levels. Bombesin (1 ng/ml) promoted
further, significant loss of peptide, which was dependent on
extracellular Ca2+ and inhibited by somatostatin and [D-Arg1, D-Pro2,
D-Trp7,9, Leu11] Substance P, a bombesin receptor antagonist. CGRP
staining of explants incubated with 24 mM HCO3- maintained no-release
levels at and above pH 7.1 but decreased significantly at pH 6.8. The
drop was blocked by somatostatin or exclusion of HCO3- and not
augmented by bombesin or 48 mM HCO3-. Results suggest pulmonary
endocrine cells may respond to hypercapnia by releasing bioactive
peptides like CGRP, thus stimulating afferent nerves and altering
patterns of ventilation and perfusion.
Received 12 July 1995; accepted in final form 17 September 1996.
APS Manuscript Number L218-5.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996