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

点击翻译按钮获取中文摘要

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.