Figure 1.

OIRKO mice are smaller in size, with slighter bones. PCR of the IR locus revealed that recombination of floxed IR alleles occurs only in bone ((a), ΔIR; calvaria, tibia). OIRKO mice exhibited an ~80% decrease in IR in whole bone by Western blot (n = 3 IR flox, 3 OIRKO tibiae, (b)). Loss of the insulin receptor in osteoblasts reduced the size of male and female mice. Postnatal growth curves for male ((c), top) and female ((c), bottom) IR flox and OIRKO mice are shown (*P < 0.05, **P < 0.01, and ***P < 0.001). Disruption in the growth plate was not apparent (a representative H & E stain is shown, (d)). μCT images of the femur midshaft demonstrated that femurs from OIRKO mice are narrower than from comparably aged IR flox mice (e).