Differential effects of gonadal function on bone histomorphometry in male and female rats

Abstract

The effects of castration on bone histomorphometry and mineral homeostasis were compared in male and female rats. Measurements were performed 4 weeks after sham operation or gonadectomy. Orchiectomy produced increases in serum calcium and decreases in serum testosterone and androstenedione, whereas ovariectomy produced decreases in serum estradiol and testosterone. Orchiectomy did not alter static bone histomorphometric measurements of the tibial diaphysis, whereas ovariectomy increased cross-sectional and medullary areas, lowered endosteal tetracycline-labeled surface length, and markedly increased endosteal nonlabeled surface length. Orchiectomy decreased mean periosteal bone formation rate and mean periosteal bone apposition rate, whereas ovariectomy increased both measurements. Orchiectomy and ovariectomy markedly diminished trabecular area and trabecular surface length at the tibial metaphysis. Orchiectomy did not alter the number of osteoclasts per mm trabecular surface or the percentage of trabecular surface covered by osteoclasts, whereas ovariectomy increased both measurements. These findings indicate that gonadal hormones produce separate and distinct effects on bone metabolism as determined by histomorphometry in male and female rats.

Influence of intermittent administration of parathyroid hormone on muscle tissue and bone healing in orchiectomized rats or controls

“…As age-, gender-, and muscle-specific differences could be found in the response to PTH treatment, the effect of PTH on metabolic and structural properties of the two limb muscles gastrocnemius and soleus and the back muscle longissimus was analyzed. Rats display deleterious changes in bone 4 weeks after orchiectomy (Turner et al 1989) and represent a valuable experimental model for osteoporotic studies (Wink & Felts 1980). The clear decrease in serum testosterone verified the success of orchiectomy in the present study.…”

“…Although fracture healing is supposed to be impaired in osteoporotic organisms (Namkung-Matthai et al 2001, bone bridging in Orx rats occurred earlier than in sham rats (days 27 vs 32). Decreased callus area in Orx rats may be a consequence of diminished bone formation rate and periosteal apposition rate reported in rats after orchiectomy (Turner et al 1989). Elevated serum OC level in all animals treated with PTH indicated increased osteoblast activity that may promote further bone synthesis and bone healing.…”

Supraphysiological testosterone enanthate administration prevents bone loss and augments bone strength in gonadectomized male and female rats

“…Conversely, TE administration prevented trabecular bone loss in males, which appears consistent with previous research (58) and, at least partially, prevented high-turnover osteopenia in females, as indicated by reductions in urinary deoxypyridinoline/creatine and serum osteocalcin compared with GX animals, although TE was unsuccessful in completely maintaining CBV in females. Previous research indicates that supraphysiological testosterone administration is capable of preventing cortical and cancellous bone loss in GX male rats (46,47) and cortical bone loss in GX female rats (47). Overall, our results indicate that supraphysiological TE administration completely prevents cancellous bone loss in GX males, but not GX females, suggesting that physiological estradiol replacement may be necessary to completely prevent hypogonadism induced CBV loss in females.…”

Prepubertal OVX increases IGF-I expression and bone accretion in C57BL/6J mice

“…Therefore, two mechanisms are involved in regulating sex differences observed in bone accretion during puberty. Increased testosterone in males increases periosteal bone formation as demonstrated by reduced axial and appendicular bone size and reduced mineral in orchidectomized male rats during puberty (45,59). In addition, loss of the androgen receptor results in reduced periosteal BFR in mice (52).…”