VITAMIN D AND CALCIUM IN LACTATING AND SUCKLING RATS

拟议研究的长期目标是：1)确定 肠道钙调节的影响因素及相互关系 哺乳期对甲状旁腺激素的吸收和分泌 测定维生素D和断奶对骨基质和血浆的影响 哺乳和新断奶仔猪体内的磷水平。具体目标 与哺乳期大鼠相关的包括确定a)之间的关系 进食、肠肥大-增生、胃泌素分泌和 甲状旁腺激素(PTH)分泌；b)皮质酮的作用， 促胰液素等胃肠激素对体内甲状旁腺激素分泌的影响 和体外；c)肠道效率之间的关系 钙的吸收与哺乳强度、高催乳素血症网 维生素中的骨吸收和电离血浆钙浓度 D缺乏和D充足的哺乳期大鼠；以及d) 饮食中的碳水化合物和维生素D与哺乳和 断奶仔鼠包括测定维生素D和断奶对 血磷水平、骨矿含量和骨胶原含量 交叉链接模式。拟议的研究将利用先前开发的 生产维生素D缺乏性哺乳大鼠的饮食程序和 哺乳仔鼠甲状旁腺放射免疫分析的标准方法 激素、皮质酮和胃泌素的体内外测定 用净吸收法测骨矿含量、钙吸收率 具有不同肠段的活体和原位环以及方法 用来测定胶原交联物的相对含量和分布 未矿化和矿化的骨基质。这些研究的结果 应该增加我们对维生素D的生理学和药理学的了解 以及参与钙代谢适应的因素和机制 在哺乳过程中，以及参与骨骼成熟和 断奶时的矿物质代谢。

The long-term objectives of the proposed research are 1) to identify factors and relationships involved in regulation of intestinal calcium absorption and parathyroid hormone secretion during lactation and 2) to determine the effect of vitamin D and weaning on bone matrix and plasma phosphate level in the suckling and newly weaned offspring. Specific aims related to lactating rats include determining a) the relationships between feeding, intestinal hypertrophy-hyperplasia, gastrin secretion and parathyroid hormone (PTH) secretion; b) the effects of corticosterone, secretin and other gastrointestinal hormones on secretion of PTH in vivo and in vitro; c) the relationship between efficiency of intestinal absorption of calcium and lactational intensity, hyperprolactinemia net bone resorption and ionized plasma calcium concentrations in vitamin D-deficient and D-replete lactating rats; and d) the interaction between dietary carbohydrate and vitamin D. Specific aims related to suckling and weaned rat pups include determining the effects of vitamin D and weaning on the plasma phosphate level, bone mineral content and bone collagen crosslink pattern. The proposed studies will utilize previously developed dietary procedures for producing vitamin D-deficient lactating rats and suckling pups, standard methods for radio-immunoassay of parathyroid hormone, corticosterone and gastrin, in vivo and in vitro determination of bone mineral content, calcium absorption determination by net absorption in vivo and with in-situ loops of different intestinal segments, and methods for determining relative amounts and distribution of collagen crosslinks in unmineralized and mineralized bone matrix. The results of these studies should increase our knowledge of physiology and pharmacology of vitamin D and of factors and mechanisms involved in adaptation of calcium metabolism during lactation, as well as mechanisms involved in maturation of bone and mineral metabolism at time of weaning.