Effects of hydrogen and bicarbonate ions on endocrine cells in fetal rat lung organ cultures.
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 after incubation in control or test media. After exposure to HCO3(-)-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-Arg(1),D-Pro(2),D-Trp(7,9),Leu(11)]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 was not augmented by bombesin or 48 mM HCO3-. Results suggest that pulmonary endocrine cells may respond to hypercapnia by releasing bioactive peptides like CGRP, thus stimulating afferent nerves and altering patterns of ventilation and perfusion.
Ebina
M
M
Department of Anatomy and Neurobiology, Boston University School of Medicine, Massachusetts 02118, USA.
Hoyt
R F
RF
McNelly
N A
NA
Sorokin
S P
SP
Linnoila
R I
RI
D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D001839:Bombesin / Q000037:antagonists & inhibitors / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D004702:Endocrine Glands / Q000166:cytology / Q000187:drug effects* / Q000196:embryology*; D005333:Fetus / Q000166:cytology; D006859:Hydrogen / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007477:Ions; D008168:Lung / Q000187:drug effects* / Q000196:embryology*; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley
D001639:Bicarbonates; D007477:Ions; D006859:Hydrogen; D001839:Bombesin; D002118:Calcium