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SUMMARY

The transplanted ovary preparation in the ewe permits long-term access to both the arterial and venous sides of the ovarian circulation in the unstressed, unanaesthetized animal. However, these animals are not completely normal, as the separation of the ovary from the uterus results in ovarian cycles with a prolonged luteal phase and the infrequent manifestation of behavioural oestrus. Treatment with exogenous gonadotrophins made it possible to carry out direct infusion experiments on the transplanted ovary on a more uniform basis. The effect on ovarian blood flow and on ovarian steroid secretion following the infusion of ovine luteinizing hormone (LH), ovine follicle-stimulating hormone (FSH) or ovine prolactin directly into the arterial supply of the transplanted ovary of the ewe is described. Four infusions of each of the three ovine pituitary gonadotrophins were made into the ovary at rates varying from 0·1 μg./hr. to 1000 μg./hr. LH infusions produced an increase in both ovarian blood flow and steroid secretion at all dosage levels employed. Androstenedione showed the greatest increase (600%) in secretion rate after LH, followed by testosterone (400%), oestradiol (more than 50%) and progesterone (less than 50%). Progesterone however showed the greatest increase in terms of mass of steroid secreted. There was no measurable change in the secretion of oestrone. Ovarian blood flow increased by at least 20% (range 20–125%) within 1 hr. of beginning the LH infusion. On the other hand FSH and prolactin infused at the same or at a higher rate than LH, had essentially no effect on ovarian blood flow or steroid secretion rate. In two out of four FSH infusions there appeared to be a transient fall in progesterone secretion rate. The infusion of 0·9% NaCl solution into the ovary as a control had no effect on blood flow or on steroid secretion.

ABSTRACT

The effects of histone subfractions on rat liver thyroid hormone receptor–DNA interaction were examined using an in-vitro DNA-cellulose binding assay. H1 histones bound to DNA showed reversible and potent inhibition of receptor–DNA binding without affecting receptor–hormone binding. Poly-lysine, bovine serum albumin, ovalbumin and cytochrome c did not alter receptor–DNA binding. H1 histone subfractions (calf thymus lysine-rich histone (CTL)-1, CTL-2 and CTL-3) showed potent inhibition of receptor–DNA binding indistinguishable from each other. The quantity of H1 histone subfractions bound to DNA was the same. Although each subfraction has different functional properties, inhibition of receptor–DNA binding was a common feature of all the H1 histone subfractions, which is important for the non-random distribution of the receptor in chromatin.

Binding of the receptor to core histones was investigated; it was found to bind to core histones more potently than to other proteins (H1 histone, ovalbumin and cytochrome c). Among core histone subfractions, H4 histone bound to the receptor most potently and is the candidate to be one of the acceptor sites of the receptor in chromatin.

Journal of Endocrinology (1989) 121, 337–341

SUMMARY

Secretion rates of ovarian steroids were measured in five ewes in which the left ovary was transplanted to the neck. Progesterone, 20α-dihydroprogesterone, androstenedione, testosterone, oestrone and oestradiol-17β were measured in samples of ovarian venous blood collected twice weekly for six periods of 4–9 weeks. The secretion of progesterone (range < 2–804 μg./hr.) showed some cyclical variation in four collection periods with a minimum estimated cycle length of 20 days. 20α-Dihydroprogesterone was present in quantities of about 1/50th of that of progesterone. The maximum secretion of oestradiol-17β (up to 250 ng./hr.) occurred at the same time as the minimum secretion of progesterone. The secretion of oestrone (0–88 ng./hr.), androstenedione (59–159 ng./hr.) and testosterone (20–90 ng./hr.) followed that of oestradiol-17β. In two animals there was a constant high secretion of progesterone throughout the collection periods, indicating the persistence of a corpus luteum. None of the ewes with transplanted ovaries showed behavioural oestrus regularly. These changes of ovarian function after transplantation to the neck could be explained by physical separation of the ovary and the uterus.

On seven occasions systemic administration of pregnant mare serum gonadotrophin (PMS, 750–1000 i.u.) was followed by a marked rise in the secretion rate of oestradiol-17β, androstenedione and testosterone. There was a progressive increase in the secretion of progesterone beginning about the 5th day after PMS in three experiments when the secretion was below 25 μg./hr. in the control samples.

Abstract

In order to study whether peripheral action of thyroid hormones is altered in insulin deficiency and to elucidate the biological consequences of alteration of the cytosolic 3,5,3′-tri-iodo-l-thyronine (T₃) binding protein (CTBP), we measured malic enzyme, T₃-responsive nuclear n protein, CTBP and nuclear thyroid hormone receptor in the liver and kidney of streptozotocin (STZ)-induced diabetic rats that were treated with or without insulin and/or a receptor-saturating dose of T₃. The following results were obtained. 1. Induction of malic enzyme by T₃ was apparently diminished in diabetic rats. However, supplementary injection of insulin enabled previously given T₃ to take effect in diabetic rats. 2. T₃-responsiveness of other hepatic proteins (n protein and CTBP) was not altered by insulin in diabetic rats. 3. The level of n protein was increased by insulin in diabetic rats in vivo and in perfused rat liver, indicating that the hepatic n protein is a novel insulin-responsive protein. T₃ and insulin increased the level of n protein non-synergistically in diabetic rat liver. 4. Hepatic nuclear receptor levels were not altered in diabetic rats. 5. Hepatic CTBP levels were decreased in diabetic rats. This was not due to the toxic effect of STZ. Low CTBP level was only partially increased by insulin after 30 days of diabetic period. Renal CTBP levels were not altered in diabetic rats with or without insulin treatment. These results indicate that reduction of CTBP did not influence the hepatic response to a receptor-saturating dose of T₃, although CTBP may regulate the nuclear T₃ transport, and that fundamental action of a receptor-saturating dose of T₃ was not attenuated in diabetic rat liver.

Journal of Endocrinology (1994) 143, 55–63

Abstract

Cellular and nuclear uptake of tri-iodothyronine (T₃) and thyroxine (T₄) was examined using the cultured cell line derived from rat liver, clone 9, and rat hepatoma, dRLH-84. The saturable cellular uptake of T₃ and T₄ was demonstrated in these cells. First we examined the cell cycle-dependent alteration of thyroid hormone uptake. Cellular T₃ uptake was minimal in the early G1 phase and increased in the late G1 phase, reaching a maximal level in the S phase. Alterations in nuclear T₃ uptake were in accordance with the changes in cellular T₃ uptake. On the other hand, cellular and nuclear T₄ uptake was unchanged throughout the cell cycle, suggesting the T₃ specificity of the cell cycle-dependent alteration of cellular hormone transport. Next we examined the effect of sodium butyrate on the cellular transport of thyroid hormones. After treatment with 5 mm sodium butyrate, cellular and nuclear uptake of T₃ was increased, reaching a maximal level (four- to sevenfold increase) after 48 h. When cells were incubated for 48 h with various concentrations of sodium butyrate, T₃ uptake was enhanced by 1 mm sodium butyrate, reaching a maximal level with 5 mm. Although cellular T₄ uptake was also increased after treatment with sodium butyrate, the degree and time-course of the increase were different from those of T₃. The maximal increase in cellular T₄ uptake (two- to threefold increase) was attained 20 h after treatment. Despite the increase in cellular T₄ uptake, nuclear T₄ uptake was decreased after treatment with sodium butyrate. For both T₃ and T₄, the enhanced cellular uptake was due to the increased V_max without changes in the Michaelis–Menten constant. These data indicate that cellular transport of T₄ is different from that of T₃ in rat hepatic cells.

Journal of Endocrinology (1995) 147, 479–485