title: Somatostatin infusion inhibits the stimulatory effect of testosterone on endosteal bone formation in the mouse.
abstract: To investigate whether the effects of testosterone (T) on endosteal bone metabolism may be mediated by growth hormone (GH), intact male mice were infused for ten days with T (5 or 15 mg/kg/d) alone, or combined either with native somatostatin (SRIF) (220 micrograms/kg/d) or with the long-acting somatostatin analog SMS 201-995. Testosterone infusion induced a dose-dependent increase in histomorphometric parameters of bone formation, causing a 25% increase in osteoblastic and osteoid surface and 10% to 12% stimulation of the matrix and mineral appositional rates. Stimulation of bone formation rate was associated with a 2- to 3-fold increase in the incidence of serum GH peaks of high amplitude. SRIF (220 micrograms/kg/d) and SMS at low dose (4.32 micrograms/kg/d) decreased parameters of bone formation by 20% to 25%. At a higher dosage (13 micrograms/kg/d), which mildly decreased serum glucose and longitudinal bone growth, SMS further reduced bone formation rate. Infusion of SRIF with T (5 mg/kg/d) blunted the stimulatory effect of T. Similarly, infusion of a high dose of SMS (13 micrograms/kg/d), together with T (15 mg/kg/d), abolished the effect of T (15 mg/kg/d) without altering serum glucose or mineral levels. The effect of SRIF on testosterone-induced (5 mg/kg/d) bone formation was associated with inhibition of T-induced high-amplitude GH peaks. The results indicate that T stimulates the osteoblastic bone formation in association with increased GH secretion, whereas SRIF and the analog SMS produce inhibitory effects.
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight / Q000187:drug effects; D013006:Growth Hormone / Q000097:blood; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D015282:Octreotide; D010012:Osteogenesis / Q000187:drug effects*; D013004:Somatostatin / Q000031:analogs & derivatives / Q000494:pharmacology*; D013739:Testosterone / Q000494:pharmacology*
chemical_list: D001786:Blood Glucose; D013739:Testosterone; D013004:Somatostatin; D013006:Growth Hormone; D015282:Octreotide