title: Smooth muscle myosin regulation by serum and cell density in cultured rat lung connective tissue cells.
abstract: RNA and protein analyses were used to detect expression of SM1 and SM2 smooth muscle myosin heavy chain (MHC) in cultured adult rat lung connective tissue cells (RL-90). Smooth muscle MHC mRNA expression in confluent cells grown in 10% serum was approximately 50% of the level in adult stomach. Similar results were obtained in cells cultured at low density (25% confluency) in 1% serum. However, in low-density cultures transferred to 10% serum for 24 h, the level of MHC mRNA decreased to approximately 20% of that in adult stomach. Smooth muscle alpha-actin showed a pattern of expression similar to that for smooth muscle MHC. Expression of nonmuscle MHC-A mRNA was higher in all culture conditions compared to stomach. MHC-A mRNA expression was less in low-density cultures in low serum and increased when low-density cultures were transferred to 10% serum for 24 h. MHC-B mRNA expression was less in low- vs. high-density cultures. In contrast to MHC-A, however, MHC-B mRNA expression in low-density cultures was higher in low serum. Immunofluorescence and immunoblotting with SM1-specific antibody demonstrated the presence of the SM1 protein isoform as well as reactivity to a protein band migrating slightly faster than SM2. These results demonstrate that cultured rat lung connective tissue cells express smooth muscle MHC and that expression is modulated by culture conditions.
authors.affiliation: Department of Physiology and Biophysics, University of Vermont, Burlington 05405.
authors.forename: P
authors.initials: P
authors.lastname: Babij
authors.forename: J
authors.initials: J
authors.lastname: Zhao
authors.forename: S
authors.initials: S
authors.lastname: White
authors.forename: J
authors.initials: J
authors.lastname: Woodcock-Mitchell
authors.forename: J
authors.initials: J
authors.lastname: Mitchell
authors.forename: M
authors.initials: M
authors.lastname: Absher
authors.forename: L
authors.initials: L
authors.lastname: Baldor
authors.forename: M
authors.initials: M
authors.lastname: Periasamy
authors.forename: R B
authors.initials: RB
authors.lastname: Low
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001790:Blood Physiological Phenomena; D002452:Cell Count; D002478:Cells, Cultured; D003238:Connective Tissue / Q000201:enzymology*; D003239:Connective Tissue Cells; D007158:Immunologic Techniques; D007527:Isoenzymes / Q000378:metabolism; D008168:Lung / Q000166:cytology / Q000201:enzymology*; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000201:enzymology*; D009218:Myosins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats
chemical_list: D007527:Isoenzymes; D012333:RNA, Messenger; D009218:Myosins