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The effect of SrCl(2) treatment on bone nanostructure in a rat ovariectomy model was studied using scanning small-angle X-ray scattering (sSAXS). Twelve 6-month-old female Wistar rats were used. Six animals were ovariectomized (+ovx) and six were left intact after sham surgery (-ovx). Six animals, three +ovx and three -ovx, were treated with 4 mmol SrCl(2) (aq)/kg/day (+Sr), whereas the remaining six received placebo (-Sr) for 140 days. Rats were labeled with flourochromes at days 7, 126, and 136. Femoral cross sections were studied using fluorescence microscopy, scanning electron microscopy including energy-dispersive X-ray analysis, and sSAXS. The SAXS data comprised about 5,500 measurements and provided information about mineral crystal thickness and orientation in new and old bone. The newly formed bone contained higher levels of Sr(2+) in +Sr than in -Sr animals, indicating that the Sr(2+) was incorporated into the new bone. Mineral plates were significantly thicker in old bone, 2.62 nm (95% CI 2.58-2.66), than in new bone, 2.41 nm (95% CI 2.36-2.46). Surprisingly, mineral plates in new bone were significantly thicker (2.52 [95% CI 2.47-2.57] nm vs. 2.41 [95% CI 2.36-2.46] nm, P = 0.017) in +ovx rats than in -ovx rats. However, no significant effect of SrCl(2) on mineral plate thicknesses in new bone was observed. The statistical model yielded estimates of the difference in bone mineral plate thickness induced by Sr. The estimated effect of Sr was -0.09 (95% CI -0.21 to 0.03) and 0.02 (95% CI -0.10 to 0.14) nm for new bone in -ovx and +ovx rats, respectively.

The effect of growth hormone treatment on the left colon was investigated in 4-month-old Wistar rats. The animals were injected with saline (controls) or biosynthetic human growth hormone (b-hGH) in doses of 1.0 and 5.0 mg b-hGH/kg/day for 30 days. The total body weight of the rats injected with 1.0 mg b-hGH/kg/day did not differ from that of the control group, whereas the body weight of the rats injected with 5.0 mg b-hGH/kg/day was increased by 37% compared with the control group. The colonic dry weight per unit length was increased by 57% and 46% by 1.0 mg and 5.0 mg b-hGH/kg/day, respectively. The defatted dry weight was increased by 52% and 44%, respectively. The hydroxyproline content per unit length was increased by 31% and 23%, respectively. Furthermore, the biomechanical strength was increased by the b-hGH injections. No difference between the two b-hGH doses was found in any of the data.

The anabolic effect of intermittent treatment with parathyroid hormone (PTH) on cortical bone was investigated. Groups of rats were injected with human PTH (1-34) or PTH (1-84), 1.1, 3.3, 10, and 30 nmol/kg/day for 30 days. A dose-related increase in bone formation rate at the femoral middiaphysis was found at both the periosteum and the endosteum and also an increase in bone mass, with no change in the bone lengths or body weight gain of the rats. The highest mineral apposition rate, as analyzed by tetracycline labeling, was found at the periosteal postero-medial aspect and at the endosteal anterior aspect. This pattern of bone modeling was also found in the PTH-treated animals, although more and more areas were included in bone mineral apposition. The PTH treatments did not change the porosity of the cortical bone nor the concentration and biochemical stability of the collagen. The highest doses of PTH resulted in a slight reduction in the ash concentration of cortical bone. No differences were found between the effects of PTH (1-34) and PTH (1-84) on bone formation rate, bone mass, porosity, and biochemical parameters. Consequently, intermittent treatment with PTH increased the formation of cortical bone dose dependently, at both the periosteum and the endosteum and increased the bone mass of these growing rats, with no change in the body weight gain or femoral growth rate compared with the control animals. The responses of the cortical bone modeling were increased by the PTH treatments without changing its direction or pattern.