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Abstract
These studies were undertaken to characterize the exocytotic changes in purified gonadotropes by three-dimensional imaging using scanning electron microscopy. Rat gonadotropes were purified using a fluorescence-activated cell sorter and an argon laser treatment system. The purified gonadotropes were stimulated with GnRH under various conditions and fixed for scanning electron microscopy. After the GnRH stimulation, many 'hole' structures (diameter 0·1–0·5 μm) were observed on the cell surface, and notably the population of cells with 10 or more holes was clearly increased. The pattern of the time-course of the changes in this population was perfectly consistent with the LH secretory profile of pituitary cells, and their formation of the cells with 10 or more holes was completely inhibited by pretreatment with a GnRH antagonist. Our data suggest that the hole structure represents an exocytotic opening site and that regulated exocytosis in purified gonadotropes can be evaluated by scanning electron microscopy. This method may be widely applicable to other endocrine cells.
Journal of Endocrinology (1995) 144, 193–200
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Abstract
The effects of interleukin (IL)-1 and granulocytemacrophage colony stimulating factor (GM-CSF), which are present in the mouse placenta, on the secretion of mouse placental lactogen (mPL)-1 and mPL-II by placental cells were tested in vitro. IL-lα and IL-1β, 2·5 nmol/l each, significantly inhibited mPL-II secretion by cells from days 9 and 12 of pregnancy, but did not affect mPL-II secretion by cells from day 7 of pregnancy or mPL-I secretion by cells from days 7, 9 or 12 of pregnancy. GM-CSF had no effect on mPL-I and mPL-II secretion by cells from days 7, 9 or 12 of pregnancy. The inhibitory effects of IL-1α and IL-1β on mPL-II secretion were completely eliminated by the addition of antibodies to IL-1α and IL-1β respectively. Western blot analysis for mPL-II indicated that IL-1α significantly reduced the intensity of the mPL-II band. Steady-state levels of mPL-II mRNA, assessed by Northern blot analysis, were reduced by incubation of placental cells from day 12 of pregnancy with 2·5 nmol/l IL-1α for 5 days. Co-incubation of 0·25 pmol/l IL-1α, 25 pmol/l IL-6, and 25 pmol/l tumor necrosis factor-α, each of which did not significantly inhibit mPL-II secretion by itself, together inhibited mPL-II secretion. These results suggest that IL-1, but not GM-CSF, is a potent inhibitor of mPL-II secretion after mid-pregnancy, and that the combined action of cytokines can inhibit mPL-II secretion.
Journal of Endocrinology (1995) 147, 423–429
