title: [Operational mechanism modification of bone mechanostat in an animal model of nutritional stress: effect of propranolol].
abstract: BACKGROUND
  Propranolol (P) treatment exerts a preventive effect against the detrimental consequences to bone status in mildly chronically food-restricted growing rats (NGR) by an increment in cortical bone and by improving its spatial distribution.
  
  
  OBJECTIVE
  To study the effect of beta-blocker on operational mechanism of bone mechanostat in an animal model of nutritional stress.
  
  
  METHODS
  Weanling male Wistar rats were randomly assigned to four groups: control (C), C + P (CP), NGR and NGR + P (NGRP). C and CP rats were fed freely with the standard diet. NGR and NGRP rats received, for 4 weeks, 80% of the amount of food consumed by C and CP respectively, the previous day, corrected by body weight. Propranolol (7 mg/kg/day) was injected ip 5 days per week, for four weeks in CP and NGRP rats. C and NGR received saline injections at an identical dosage regimen. Body weight and length were determined during the experimental period. Dietary intake was registered daily. Animals were sacrificed after 4 weeks of food restriction. Immediately, cuadriceps, femur and tibiae from each animal were dissected and weighed, and histomorphometric and mechanical studies were performed. Serum a-CTX, osteocalcin, intact PTH, calcium and phosphorous were determined. Body protein (% prot) was measured in all groups.
  
  
  RESULTS
  Food restriction induced detrimental effects on body and femoral growth, load-bearing capacity (Wf), % prot and cuadriceps weight in NGR us. C (p < 0.01). beta-blocker did not modify anthropometric and bone morphometric parameters in NGRP and CP us. NGR and C, respectively (p > 0.05). However, Wf NGRP vs. NGR was significantly higher (p < 0.01). alpha-CTX was significantly higher in NGR vs. C (p < 0.01). No significant differences were observed in alpha-CTX levels between CP, NGRP and C (p > 0.05). Serum osteocalcin, intact PTH, calcium and phospho- rous showed no significant difference between groups (p > 0.05).
  
  
  CONCLUSIONS
  These results suggest that modeling increase in bone mass and strength in NGRP rats could be due to an anticatabolic interaction of the beta-blocker propranolol on operational mechanism of bone mechanostat in an animal model of nutritional stress.
authors.affiliation: Citedra de Fisiología, Universidad de Buenos Aires, Argentina.
authors.forename: Patricia Mabel
authors.initials: PM
authors.lastname: Pintos
authors.forename: Christian Esteban
authors.initials: CE
authors.lastname: Lezón
authors.forename: Clarisa
authors.initials: C
authors.lastname: Bozzini
authors.forename: Silvia María
authors.initials: SM
authors.lastname: Friedman
authors.forename: Patricia Mónica
authors.initials: PM
authors.lastname: Boyer
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D015415:Biomarkers; D001835:Body Weight / Q000187:drug effects; D001848:Bone Diseases, Developmental / Q000097:blood / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D016723:Bone Remodeling / Q000187:drug effects; D024042:Collagen Type I / Q000097:blood; D055119:Elastic Modulus / Q000187:drug effects; D005269:Femur / Q000187:drug effects / Q000473:pathology; D005508:Food Deprivation / Q000502:physiology*; D006130:Growth Disorders / Q000097:blood / Q000209:etiology / Q000473:pathology / Q000517:prevention & control*; D008297:Male; D044342:Malnutrition / Q000188:drug therapy / Q000503:physiopathology*; D008903:Minerals / Q000097:blood; D018482:Muscle, Skeletal / Q000187:drug effects / Q000473:pathology; D009929:Organ Size / Q000187:drug effects; D010281:Parathyroid Hormone / Q000097:blood; D010455:Peptides / Q000097:blood; D011433:Propranolol / Q000494:pharmacology / Q000627:therapeutic use*; D011506:Proteins / Q000032:analysis; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D016474:Weight-Bearing
chemical_list: D000319:Adrenergic beta-Antagonists; D015415:Biomarkers; D024042:Collagen Type I; D008903:Minerals; D010281:Parathyroid Hormone; D010455:Peptides; D011506:Proteins; C052929:collagen type I trimeric cross-linked peptide; D011433:Propranolol