title: Effects of vigorous exercise training and beta-agonist administration on bone response to hindlimb suspension.
abstract: The effectiveness of dobutamine (Dob) in preventing bone loss during 14 days of hindlimb suspension (Sus) was tested in exercise-trained (Ex; n = 25) and sedentary (Sed; n = 22) rats (age 155 days). One-half of each group was given Dob (2 mg . kg-1 . day-1) or saline (Sal). Histomorphometric measurements at midfemur revealed a 17% smaller cortical bone area (CBA) and a 32% lower periosteal mineral apposition rate (MAR) in suspended vs. nonsuspended Sed/Sal rats. Dob abolished this decline in CBA in Sed/Sus rats, probably via an attenuation of the decrease in periosteal MAR; similar but nonsignificant effects on cross-sectional moment of inertia were observed. Nonsuspended Ex rats had no change in bone CBA when CBA is indexed to body weight. Sus appeared to uncouple the relationship between soleus weight and CBA. Dob attenuated the 43% decline in soleus weight after Sus in Ex but not in Sed rats. In summary, vigorous Ex before Sus does not affect loss of bone mass due to unloading; Dob effectively maintains CBA in Sed rats subjected to suspension.
authors.affiliation: School of Health, Physical Education, and Recreation and Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio 43210-1290, USA.sbloom@acs.tamu.edu
authors.forename: S A
authors.initials: SA
authors.lastname: Bloomfield
authors.forename: B E
authors.initials: BE
authors.lastname: Girten
authors.forename: S E
authors.initials: SE
authors.lastname: Weisbrode
mesh_terms: D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001835:Body Weight / Q000187:drug effects / Q000502:physiology; D015519:Bone Density / Q000187:drug effects / Q000502:physiology; D001842:Bone and Bones / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology*; D004280:Dobutamine / Q000494:pharmacology; D018475:Head-Down Tilt; D019417:Hindlimb Suspension; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology*; D009929:Organ Size / Q000187:drug effects / Q000502:physiology; D010805:Physical Conditioning, Animal / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000318:Adrenergic beta-Agonists; D004280:Dobutamine