Ultrastructural and physiological studies on the function of pituitary intermediate lobe in mice.

本研究证实了口服尿素引起小鼠垂体中间叶(PIL)细胞高分泌的新事实。口服尿素是第三个刺激PIL细胞精细结构的因素，除了我们先前对饮食钠缺乏(1974,1976)和实验性多饮(1984)的研究外。超微结构和形态计量学研究概述如下：(1)添加1%尿素的流食乳鼠PIL细胞的变化。哺乳母猪(哺乳期第12-17天)饲喂流质日粮(11.5%奶粉)或含1%尿素的流质日粮。形态计量学研究表明，饲喂含尿素液体饲料的雄性小鼠PIL细胞的高分泌明显高于添加1%尿素的液体饲料对照组。(2)添加1%尿素的液体饲料对雄性小鼠PIL细胞的影响。用含1%尿素的液体饲料喂养幼年雄性小鼠10天，以确定口服尿素是否既能刺激哺乳期小鼠的PIL细胞，又能刺激雄性小鼠的PIL细胞。形态计量学分析结果表明，口服尿素对雄性小鼠PIL细胞的分泌活性有明显的刺激作用。(3)含6%、12%和24%尿素的颗粒状食物连续14天对雄性小鼠PIL细胞的分泌活动有明显的刺激作用。形态计量学结果显示，含尿素颗粒组小鼠PIL细胞的分离活性呈剂量依赖性增加。用水量也与采用的尿素浓度平行增加。这些结果解释说，口服尿素刺激PIL细胞的机制是：(1)下丘脑对PIL细胞的抑制控制减弱；(2)PI激素参与过量尿素的排泄；(3)高血尿素浓度引起的低钠血症。

The present studies demonstrated a new fact that oral urea administration resulted in hypersecretion of pituitary intermediate lobe(PIL) cells in mice. Oral urea is the third factor, besides our previous studies of dietary Na-deficiency (1974,1976) wid of experimental polydipsia (1984), that stimulates PIL cells in fine structure. The outline of the ultrastructural and morphometric studies is described as follows:(1) Alterations in PIL cells of suckling mice fed a liquid diet supplemented with 1% urea. Suckling dams (day 12-17 of lactation) were fed with either a liquid diet (11.5% powdered milk) or the liquid diet containing 1% urea. Morphometric study resulted in the hypersecretion in PIL cells of dams being given the urea-containing liquid diet more significantly than that of the liquid diet control.(2) Alterations in PIL cells of male mice fed a liquid diet supplemented with 1% urea. Young adult male mice were fed with the liquid diet containing 1% urea for 10 days in order to ascertain whether oral urea could stimulate PIL cells not only in lactating dams but also in male mice. The morphometric analysis showed the result that oral urea stimulated significantly the secretory activity of PIL cells in male mice.(3) Alerations in PIL cells of male mice given the pelleted food containing urea in the concentration of 6%, 12% and 24% for 14 days. Morphometric result revealed the increment of segretion activity in PIL cells of mice given urea- containing pellets in a dose dependent manner. Water consumption also increased in parallel to the urea concentrations adopted. These results are interpreted that oral urea stimulation of PIL cells is through a mechanism of either (1)attenuation of hypothalamic inhibitory control over PIL cells or (2)an involvement of PI hormones in the excretion of excess urea, or (3) hyponatremia caused by high blood urea concentration.