title: Loading-related increases in prostaglandin production in cores of adult canine cancellous bone in vitro: a role for prostacyclin in adaptive bone remodeling?
abstract: Cyclic mechanical loading sufficient to engender strains of physiologic magnitude applied to recently excised canine cancellous bone cores in vitro increased the release of prostaglandin E (PGE) and prostacyclin (PGI2, measured as its breakdown product 6-keto-PGF1 alpha), during a 15 minute loading period in which PG levels were measured in perfusing medium at 5 minute intervals. Peak production occurred in the 0-5 minute sample. Mean levels preload compared to during load were PGE, 2.66 and 3.67 ng/ml (p less than 0.002); and 6-keto-PGF1 alpha, 543 and 868 pg/ml (p less than 0.007). The elevated levels then declined to preload levels during the loading period. However, the 5-10 minute but not the 10-15 minute samples still contained levels greater than preload values. A second 15 minute period of load, 1 h following the end of the first, produced smaller increases in the levels of release that were statistically significant only for the first 0-5 minute sample during load (preload compared to load mean values, PGE, 1.09-1.66 ng/ml, p less than 0.02; 6-keto-PGF1 alpha, 401-558 pg/ml, p less than 0.04). Immunolocalization revealed PGE and 6-keto-PGF1 alpha in lining cells and 6-keto-PGF1 alpha but not PGE in osteocytes. Addition to the medium of 1 microM PGE2, approximating the concentration produced by loading, had no significant effect on the specific activity of the extractable RNA fraction labeled with [3H]uridine, whereas 1 microM PGI2 produced an increase similar to that seen previously with loading.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Veterinary Basic Sciences, Royal Veterinary College, London, England.
authors.forename: S C
authors.initials: SC
authors.lastname: Rawlinson
authors.forename: A J
authors.initials: AJ
authors.lastname: el-Haj
authors.forename: S L
authors.initials: SL
authors.lastname: Minter
authors.forename: I A
authors.initials: IA
authors.lastname: Tavares
authors.forename: A
authors.initials: A
authors.lastname: Bennett
authors.forename: L E
authors.initials: LE
authors.lastname: Lanyon
mesh_terms: D015121:6-Ketoprostaglandin F1 alpha / Q000032:analysis; D000818:Animals; D016723:Bone Remodeling / Q000502:physiology*; D001842:Bone and Bones / Q000378:metabolism*; D004285:Dogs; D011464:Epoprostenol / Q000502:physiology*; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D010477:Perfusion; D011453:Prostaglandins / Q000096:biosynthesis*; D011458:Prostaglandins E / Q000032:analysis; D012313:RNA / Q000096:biosynthesis / Q000378:metabolism; D013314:Stress, Mechanical
chemical_list: D011453:Prostaglandins; D011458:Prostaglandins E; D015121:6-Ketoprostaglandin F1 alpha; D012313:RNA; D011464:Epoprostenol