Spinal deformity frequently produced by pinealectomy and the role of melatonin on developing the spine in chicks

脊椎的发育是所有脊椎动物最重要的过程之一。在我们以前的研究中，即使在松果体切除术后2个月，松果体切除层的脊柱畸形率仍约为70%。本研究采用切除松果体的方法，观察了肉鸡脊柱畸形的发生率。去松果体肉鸡8日龄和15日龄脊柱畸形率分别为70%和100%，其中15日龄严重畸形率为63%。褪黑激素能显著降低去松果体肉鸡脊柱畸形的发生率和程度。结果表明，肉鸡脊柱畸形率明显高于蛋鸡。因此，在下一步中，调查身体生长对脊柱畸形程度的影响。将2日龄切除松果体的肉仔鸡分别在全饲粮、80%饲粮和60%饲粮下饲养8天。脊柱畸形发生率在三组间差异不显著。这些结果表明，松果体切除鸡脊柱畸形的诱发与机体生长无关。在接下来的研究中，我们检查了松果体的去除是否会改变骨矿物质和血浆钙浓度。松果体切除后第7天，椎体中钙、磷含量显著低于对照组，而血浆中钙含量则显著升高。在膳食中添加3倍钙可降低脊柱畸形的比例和程度。这些结果表明，在鸡脊柱发育过程中，松果体影响骨代谢。

The developing the spine is one of the most important process in all vertebrates. In our previous study the rate of deformity of the spine in pinealectomized layers was about 70% even though 2 months after pinealectomy. In the present study we examined the rate of spinal deformity in broilers by pinealectomy. The rate of spinal deformity in pinealectomized broilers at 8 day- and 15 day-old was 70 and 100% respectively, in which severe deformity at 15 day-old was 63%. Administration of melatonin in pinealectomized broilers significantly decreased the ratio and degree of spinal deformity. These results show the rate of the deformity of the spine in broilers was much higher than that of layers. Therefore, in the next step, the influence of body growth on the degree of spinal deformity was investigated. Pinealectomized broilers at 2 day-old were kept under dietary foods for 8 days ; full diet, 80% diet or 60% diet, respectively. The ratio of spinal deformity was not significant deferent among three dietary groups. These results show that the induction of spinal deformity in pinealectomized chicks is independent on the body growth. In the next study we examined whether the removal of the pineal gland changes bone minerals and plasma Ca concentrations. Calcium and phosphorus levels in the vertebra at 7 days after pinealectomy were significantly lower than those of controls, and on the other hand the plasma Ca concentrations significantly increased. Administration of 3-fold Ca on dietary food decreased the ratio and degree of spinal deformity. These results suggest that the pineal gland affects the bone metabolism in the process of developing chick spine.