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Abstract. The present study was designed to characterize bihormonal cells in rat pituitary cells which secrete PRL and gonadotropins.This was done by using sandwich cell immunoblot assay (CIBA) and reverse hemolytic plaque assay (RHPA) in combination with immunocytochemistry (ICC) and by measuring the intracellular free calcium concentration ([Ca2+];). The result of the experiment with sandwich CIBA revealed that the populations of LH-and FSH-secreting cells in the PRL-secreting cells were 6.23% and 5.91%, respectively, and the populations of the PRL secreting cells in the LH-and FSHsecreting cells were 18.4% and 15.5%, respectively. Additional studies by the combined techniques of RHPA with ICC revealed that the populations of LH-and FSH-containing cells in the PRL secreting cells were 4.43% and 2.40%, respectively, which were consistent with the results of Sandwich CIBA. Some of the PRL-secreting cells determined by RHPA showed responsiveness to TRH and GnRH in [Ca2+];. These results suggest that bihormonal cells which secrete both PRL and LH, or both PRL and FSH are present in the normal rat pituitaries.

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 micron) 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.

The consecutive findings of the magnetic resonance (MR) imaging in a patient with nonmetastatic trophoblastic disease are reported. On MR image, there are noted two kinds of MR findings which suggest the existence of trophoblastic disease; one was a typical hypervascular mass of heterogeneous signal intensity within myometrium, and the other was the increase in myometrial and parametrial flow void. The former finding appeared only for a short period while the disease was highly active. The latter finding well paralleled the serum human chorionic gonadotropin (hCG) level, and the remarkable flow void, indicating dilatated blood vessels, disappeared with the complete remission of the disease. These findings suggest that MR imaging may be useful for diagnosing and following gestational trophoblastic disease.