title: Circadian rhythm of surfactant protein A, B and C mRNA in rats.
abstract: BACKGROUND
  All organisms have developed an internal timing system capable of reacting to and anticipating environmental stimuli with a program of appropriately timed metabolic, physiologic and behavioral events. The alveolar epithelial type II cell of the mammalian lung synthesizes, stores, and secretes a lipoprotein pulmonary surfactant, which functions to stabilize alveoli at low lung volumes.
  
  
  METHODS
  The authors investigated the diurnal variation of surfactant protein A, B and C mRNA accumulation. The diunal variation on gene expression of surfactant protein A, B and C was analysed using filter hybridization at 9 a.m., 4 p.m. and 11 p.m. Lung SP-A protein content was determined by double sandwich ELISA assay using a polyclonal antiserum raised in rabbits against purified rat SP-A.
  
  
  RESULTS
  1. The accumulation of SP-A mRNA at 4 p.m. was significantly decreased by 23.5% compared to the value at 9 a.m. (p < 0.05). 2. The accumulation of SP-B mRNA at 4 p.m. and 11 p.m. was decreased by 15.1% and 5.7%, respectively, compared to the value at 9 a.m. (p = 0.07, p = 0.69). 3. The accumulation of SP-C mRNA at 4 p.m. and 11 p.m. was decreased by 6.8% and 7.7%, respectively, compared to the value at 9 a.m. (p = 0.38, p = 0.57). 4. Total lung SP-A content at 4 p.m. and 11 p.m. was increased by 5.3% and 15.9%, respectively, compared to the value at 9 a.m. (p = 0.64, p = 0.47).
  
  
  CONCLUSIONS
  These findings represent the diurnal variation of surfactant proteins mRNA expression in vivo. These results indicated that the diurnal variation of significant gene expression is observed in hydrophilic surfactant protein rather than in hydrophobic surfactant proteins.
authors.affiliation: Department of Medicine, Hanyang University College of Medicine, 17 Haengdang-dong, Sungdong-gu, Seoul 133-792, Korea.
authors.forename: Chung Mi
authors.initials: CM
authors.lastname: Kim
authors.forename: Jang Won
authors.initials: JW
authors.lastname: Sohn
authors.forename: Ho Joo
authors.initials: HJ
authors.lastname: Yoon
authors.forename: Dong Ho
authors.initials: DH
authors.lastname: Shin
authors.forename: Sung Soo
authors.initials: SS
authors.lastname: Park
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D037661:Pulmonary Surfactant-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D037661:Pulmonary Surfactant-Associated Proteins; D012333:RNA, Messenger