FIGURE 4.

Ability of estrogen to increase bone mass in ovariectomized mice is dependent on OTRs. Shown are areal BMD (aBMD; PIXImus) measurements at the spine and femur of sham-operated (control (Ctr)) and ovariectomized (OVX) OTR^−/− and wild-type (OTR^+/+) mice that were injected with 17β-estradiol (E2; 50 μg/kg) or placebo biweekly (cumulative dose of 100 μg/kg/week). A and B, effect of ovariectomy versus sham operation in the two genotypes. C and D, effect of 17β-estradiol versus placebo within the various groups. Statistics were as follows: means ± S.E. of the percent change shown using the respective controls (n = 5–6/group) and Student's t test with the Bonferroni correction, comparing ovariectomized versus control mice (A and B) and 17β-estradiol versus zero dose (C and D) (*, p < 0.05; **, p < 0.01).