| Summary: | 博士 === 東海大學 === 畜產學系 === 92 === In this dissertation, the effects of aging on calcium homeostasis and bone status of senescence accelerated mice P8 (SAMP8) were investigated to evaluate the suitability of SAMP8 mice as an animal model for osteoporosis and the effects of dietary antler supplementation on bone metabolism-related parameters. Five experiments were conducted.
In Experiment 1, female SAMP8 and SAMR1 (control strain) mice were sacrificed and the blood and femur samples were collected initially at 2.5 months of age, and then monthly from 3 to 12 months of age. The determined bone metabolism-related parameters were plasma levels of calcium, phosphorus, calcitonin (CT), parathyroid hormone (PTH), and 1,25-dihydroxycholecalciferol (1,25(OH)2D3), and density and calcium content of femur. All parameters above were also determined in other 4 individual experiments. The results indicated that the plasma calcium levels did not change with age and were maintained within a narrow range throughout the experiment. The plasma levels of phosphorus and CT decreased, and PTH and 1,25(OH)2D3 increased with age in female mice. The curves of these parameters were shifted to the left in SAMP8, as compared to SAMR1. The femoral densities and calcium contents increased with age from the beginning of the experiment, peaked at 6 months of age, then followed by a decline in both strains. The curves for SAMP8 were lower than those for SAMR1.
In Experiment 2, the male SAMP8 and SAMR1 mice were sampled as their female counterparts in Experiment 1. The results and conclusions were similar to those obtained in Experiment 1.
In Experiment 3, the female and male SAM mice were gonadectomized or sham operated at 2 months of age, and the animals were sacrificed at 3, 6, and 12 months of age. The results showed that the plasma phosphorus levels were lower, and the 1,25(OH)2D3 levels were higher in the females than those in the males. However, there were no significant differences in the other parameters between genders. Gonadectomy increased the plasma PTH and 1,25(OH)2D3 levels, but decreased the plasma phosphorus and CT levels and the femoral densities as well as calcium contents.
In Experiment 4, the female SAMP8 and SAMR1 were ovariectomized or sham operated at 2 months of age and fed with either 0.2% antler containing diet or control diet. Animals were sacrificed at 3, 6, 9, 12, and 15 months of age. In the meanwhile, the feces and urine were collected and analyzed, and the amounts of dietary intake were recorded for 7 days in each occasion to determine the apparent digestibility and urinary excretion of calcium and phosphorus. The results showed that the apparent digestibility of calcium and phosphorus decreased and the urinary excretion of calcium and phosphorus increased with age. The apparent digestibility of calcium and phosphorus was lower, and the urinary calcium and phosphorus level was higher in the ovariectomized mice than that in the intact mice. The decrease of plasma phosphorus and CT levels, the femoral densities and calcium contents, and the increase of plasma PTH levels were moderated, and the intestinal absorption and the renal reabsorption of calcium and phosphorus were promoted by antler administration in both ovariectomized and intact mice. However, there was no effect of the dietary antler supplementation on the plasma 1,25(OH)2D3 level in the female mice.
In Experiment 5, the male SAMP8 and SAMR1 were orchidectomized or sham operated at 2 months of age, and the rest of the treatments was the same as that in Experiment 4. The results and conclusions were similar to those in Experiment 4.
It is concluded that SAMP8 is more valuable in studying age-related bone metabolism as compared to normal strains, and the gonadectomized SAMP8 is a good animal model for osteoporosis research. In addition, the prolonged dietary antler supplementation has the positive effects on bone loss.
|
|---|
