初代培養肺胞II型上皮細胞に発現するβ_1-およびβ_2-adrenoceptor mRNA量の変化 [in Japanese] Changes in β_1-and β_2-adrenoceptor mRNA levels in alveolar type II cells during cultivation [in Japanese]
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Alveolar type II cells synthesize and secrete pulmonary surfactant. Type II cells maintained on tissue culture plastic lose their diffrentiated functions and become flattened like alveolar type I cells. This phenotypic change observed in these cells <I>in vitro</I> has been suggested to represent differentiation of type II cells to type I cells. However, the analysis of this phenotypic progression demands specific functional markers to both cells. We have previously reported that both β<SUB>1</SUB> and β<SUB>2</SUB>-adrenoceptors coexist in type II cells and both receptors are involved in pulmonary surfactant secretion. In some cell types the expression levels of β-adrenoceptor mRNAs change with a process of cell differentiation. In this study, therefore, we determined the levels of mRNA for β<SUB>1</SUB>- and β<SUB>2</SUB>-adrenoceptor in cultured type II cells by a quantitative RNase protection assay, developed by us.<BR> The mRNA levels for β<SUB>1</SUB> and β<SUB>2</SUB>-adrenoceptors in the freshly isolated cells were 0.51 ± 0.07 and 1.92 ± 0.19 amol/μg total cellular RNA, respectively. These values did not change after 24 h-culture. However, in the over 48 h-cultured cells, which failed to synthesize and secrete pulmonary surfactant, only β<SUB>1</SUB> mRNA level was remarkably reduced. Dexamethasone treatment of 24 h-cultured cells caused increase in the level of β<SUB>2</SUB>-adrenoceptor mRNA, without changing that of β<SUB>1</SUB> mRNA. These results suggest that each mRNA expression may be separately regulated in cultured alveolar type II cells. The expression levels of these adrenoceptor mRNAs may be useful as a new marker in the investigation of alveolar epithelial cell differentiation.
- Folia Pharmacologica Japonica
Folia Pharmacologica Japonica 106, 112-116, 1995-09-01
The Japanese Pharmacological Society