Am. J. Respir. Cell Mol. Biol.,
Volume 20, Number 6, June, 1999 1175-1180
Expression of Serotonin Receptor 2c in Rat Type II Pneumocytes
Dashou
Wang,
Martin
Post,
and
Ernest
Cutz
Division of Pathology, Department of Pediatric Laboratory Medicine, Neonatal Research, Department of Pediatrics,
The Research Institute, MRC Group on Lung Development, The Hospital for Sick Children;
and University of Toronto, Toronto, Ontario, Canada
Serotonin (5-hydroxytryptamine [5-HT]) is a multifunctional amine with wide occurrence in both neural
and non-neural tissues, including the lung. The diverse responses to 5-HT are elicited through activation of
different 5-HT receptor subtypes. We report the expression and localization of 5-HT receptor 2c subtype
(5-HT2c-R) in rat lungs using reverse transcriptase-polymerase chain reaction, nonisotopic in situ hybridization (NISH), and immunohistochemistry. At the messenger RNA (mRNA) level, signal corresponding
to approximately 430 base pairs was detected in whole-lung tissue extracts as well as in cultures of isolated
alveolar type II cells from fetal and adult rat lung. Using antisense RNA probe for 5-HT2c-R, NISH showed strong positive signal in type II cells. The expression of mRNA signal differed between fetal and adult rat
type II cells, with weak, predominantly perinuclear localization in the former and strong cytoplasmic localization in the latter. Immunohistochemistry, using specific monoclonal antibody against 5-HT2c-R, showed
perinuclear localization in fetal type II cells; whereas in adult type II cells 5-HT2c-R immunoreactivity was
confined mostly to the plasma membrane, as demonstrated by laser confocal microscopy. Identification of
5-HT2c-R expression in alveolar type II cells suggests an important role for this amine in modulating the
function of these cells. The differences in cell domain localization between fetal and adult type II cells
could indicate developmental regulation of 5-HT2c-R expression in the lung.
