title: [The diel rhythm of PGE2 in blood of the growing rat after retractive force on mandible].
abstract: OBJECTIVE
  To study whether the orthopedic therapy will affect the rat's metabolism, the author investigates the diel rhythm of PGE2 in blood of the growing rats before and after retractive force on mandible.
  
  
  METHODS
  72 rats which were 4 weeks old and about 90 g, were divided equally and randomly into three groups: the contrast group were not exerted force, the daytime-forced group were exerted force from 8:00 am to 20:00 pm, the nighttime-forced group were exerted force from 20:00 pm to 8:00 am of the next morning. The backwards force imposed on the rats were exerted through the center of the mandibular condyle and was about 40 g(0.4 N). The period of experimentation was 7 days. In the 8th day, every 4 rats from each of the group were killed respectively at 0:00, 4:00, 8:00, 12:00, 16:00 and 20:00 to collect 3 ml blood. Then radioimmunoassay methods were used to measure the concentration of PGE2 in the blood.
  
  
  RESULTS
  In natural state, there was a diel rhythm in the concentration of PGE2 in rats' blood and the diel rhythm was related to that of endogenous PGE2 in condyle; After imposed orthopedic force to restrain mandibular growth, the normal diel rhythm of PGE2 in blood disappeared. There was no significant difference in the time-concentration curves between the contrast group and the daytime-forced group (P > 0.05), but the difference between the contrast group and the nighttime-forced group was obvious (P < 0.05) and the mesor of the nighttime-forced group was greatly decreased.
  
  
  CONCLUSIONS
  The concentration of PGE2 in rats' blood will not be affected by the orthopedic force in daytime, in nighttime. For this reason, not only the therapeutic effect but also the effect on the body's metabolism should be considerd in clinical therapy, and further researches should be carried out on whether the local orthopedic force would influence the metabolism of the whole body.
authors.affiliation: College of Stomatology, West China University of Medical Sciences.
authors.forename: G
authors.initials: G
authors.lastname: Xiong
authors.forename: Y
authors.initials: Y
authors.lastname: Chen
authors.forename: L
authors.initials: L
authors.lastname: Ye
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D015232:Dinoprostone / Q000097:blood*; D008335:Mandibular Condyle / Q000254:growth & development / Q000378:metabolism*; D017289:Orthodontic Appliances, Functional; D051381:Rats; D017208:Rats, Wistar
chemical_list: D015232:Dinoprostone