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A Watanabe, I Uchida, K Kadota, and N Katoh

We measured the amounts of a vesicular transport factor, p115/transcytosis-associated protein (p115/TAP) and its mRNA, in mammary glands from cows in which lactation was induced hormonally. The highest level of p115/TAP mRNA, determined by Northern blotting, was detected in the developing stage. In contrast to the mRNA level, the amount of protein, determined by immunoblot analysis using anti-p115/TAP antibodies raised against a p115/TAP-derived recombinant fusion protein, was higher during the lactating stages than at other times. Immunohistochemical study showed that p115/TAP was predominantly localized in mammary epithelial cells. The p115/TAP was also detected in tissues other than the mammary gland but, in contrast to the situation in the mammary gland, the protein and its mRNA levels in those tissues were independent of the stage of lactation. The increased level of p115/TAP mRNA during the developing stage and the maintenance of p115/TAP protein during lactation suggest that the synthesis of p115/TAP is regulated during mammary development and differentiation, and also that the protein is involved in a function related to lactation.

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K.-I. Maeda, H. Tsukamura, E. Uchida, N. Ohkura, S. Ohkura, and A. Yokoyama


Changes in the pulsatile secretion of LH after removal of pups and subsequent resuckling were examined in ovariectomized lactating rats, and the change after removal of pups was compared with that after the removal of ovaries in cyclic female rats. The day of parturition was designated day 0 of lactation. All lactating rats were ovariectomized on day 2 of lactation. They were deprived of their pups for 6, 12, 18, 24 or 45 h before blood sampling on day 8 of lactation, or were resuckled by their pups for 1, 4, 7 or 12 h before blood collection after separation from pups for 24 h. Cyclic female rats were ovariectomized on the day of dioestrus and blood samples were taken 12, 18, 24 or 48 h or 6 days after ovariectomy. Typical LH pulses appeared in some animals from 12 h after the removal of pups. The mean LH level and the frequency and amplitude of LH pulses gradually increased after removal of pups, until after 45 h of separation the frequency reached the high level observed 6 days after ovariectomy in cyclic rats. The subsequent resuckling by pups after a 24-h separation decreased these three parameters of LH pulses rapidly. In contrast, the frequency of LH pulses was unchanged after ovariectomy in cyclic rats, although the mean LH level and the amplitude of LH pulses increased. These results suggest that the suckling stimulus suppresses pulsatile LH secretion in a different manner from that of ovarian steroids.

Journal of Endocrinology (1989) 121, 277–283

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T Yada, K Uchida, S Kajimura, T Azuma, T Hirano, and EG Grau

To clarify the roles of prolactin (PRL) and GH in the control of the immune system, the effects of environmental salinity, hypophysectomy, and PRL and GH administration on several immune functions were examined in tilapia (Oreochromis mossambicus). Transfer from fresh water (FW) to seawater (SW) did not alter plasma levels of immunoglobulin M (IgM) and lysozyme. The superoxide anion (O(2)(-)) production in head kidney leucocytes accompanied by phagocytosis was elevated in SW-acclimated fish over the levels observed in FW fish. Hypophysectomy of the fish in FW resulted in a reduction in O(2)(-) production in leucocytes isolated from the head kidney, whereas there was no significant change in plasma levels of IgM or lysozyme. Treatment with tilapia GH and PRLs (PRL(177) and PRL(188)) enhanced O(2)(-) production in vitro in head kidney leucocytes in a dose-related manner. Extrapituitary expression of two PRLs, GH and IGF-I mRNA was detected in lymphoid tissues and cells such as head kidney, spleen, intestine and leucocytes from peripheral blood and head kidney. PRL-receptor mRNA was detected in head kidney leucocytes, and the level of expression was higher in SW-acclimated fish than that in FW fish. Treatment with PRL(177) caused higher production of O(2)(-) in the head kidney leucocytes isolated from SW tilapia than that from FW fish. In view of the fact that PRL acts antagonistically to osmoregulation in SW, its immunomodulatory actions in this euryhaline fish would appear to be independent of its osmoregulatory action.