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  • Author: Peter A. Torjesen x
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Peter A. Torjesen and Asbjørn Aakvaag

ABSTRACT

The process of luteolysis has been studied in immature rats in which superluteinization had been induced with pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotrophin (HCG). Following prostaglandin F and the prostaglandin analogues, and at the end of the pseudopregnancy, the plasma levels of progesterone and 20α-dihydroprogesterone were measured and used as parameters of luteal function in relation to the capacity of the ovarian tissue to bind LH, FSH and prolactin (PRL) in vitro. On day 19 after HCG a marked decrease in the progesterone level from the day 8 level was observed concomitant with a marked increase in 20α-dihydroprogesterone. The capacity of the ovarian tissue to bind LH in vitro was markedly reduced on day 19 compared to day 8. Identical changes were observed 21 h after 1 mg prostaglandin F or prostaglandin analogues. Progesterone decreased from about 600 ng/ml to about 50 ng/ml, whereas the increase in 20α-dihydroprogesterone was from about 200 ng/ml to 500–1000 ng/ml and the reduction in LH binding sites was from 1.7 × 10−12 to 0.5 × 10−12 mol/mg protein. Nanogram amounts of the analogues were as effective as 1 mg of prostaglandin F. The number of FSH or PRL binding sites was not affected by spontaneous luteolysis or the treatment given.

By the use of graded doses of the prostaglandin analogues a negative correlation (r=−0.81) was found between plasma progesterone and 20α-dihydroprogesterone levels, and a positive correlation (r = 0.84) between LH binding sites and plasma progesterone levels.

The luteolysis induced by prostaglandin F or prostaglandin analogues was indistinguishable from the spontaneous luteolysis using these parameters.

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Kristian F. Hanssen and Peter A. Torjesen

ABSTRACT

In 8 patients with diabetic ketoacidosis, serum prolactin was measured and found to be elevated (24.8 ± 10.2 ng/ml, mean ± sem). After correction of the ketoacidosis, the prolactin level decreased to 10.9 ± 6.4 ng/ml (normal range men 4.9 ± 0.8, women 5.1 ± 1.6 ng/ml). The scatter of prolactin values was wide. A study of the correlation between the serum prolactin values and chemical parameters that are altered in diabetic ketoacidosis was therefore undertaken. Serum prolactin values did not correlate well with the serum bicarbonate concentration or serum osmolality. However, a significant negative correlation between log serum prolactin concentration and serum sodium concentration was demonstrated (r=−0.61, P<0.001).

It is suggested that serum prolactin may possibly participate in sodium retention in man as has been demonstrated in studies on animals.

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Jens P. Berg, Peter A. Torjesen and Egil Haug

Abstract.

The FRTL-5 cell line is widely used as a model for normal thyroid follicular cells. These cells have retained their ability to alter cAMP production, cell proliferation, iodine uptake, and thyroglobulin synthesis in response to thyrotropin. We have previously shown that calcitriol attenuated both basal and TSH stimulated cAMP production dose-dependently in FRTL-5 cells. Cytosol fractions (105000 g, 60 min, 4°C) prepared from FRTL-5 cell homogenates possessed calcitriol-binding components with a sedimentation coefficient of approximately 3.7 S in high salt (0.3 mol/l KCl) sucrose gradients (5–20%). At 4°C, specific binding increased rapidly during the first 4 h and reached a plateau after 8 h. The specific binding (18 h, 4°C) was maximal at a [3H]calcitriol concentration of approximately 0.5 nmol/l. Scatchard analysis of the binding data indicated one single class of high affinity binding sites with Kd = 105±2 pmol/l and Bmax=38.5±4.7 pmol/g cytosol protein (mean ± sd, N=6). In conclusion, our results suggest that the FRTL-5 cells possess functional receptors for calcitriol with the same physicochemical properties as the receptors found in normal rat tissues.

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Marie Aanestad, J Sigurd Røtnes, Peter A Torjesen, Egil Haug, Olav Sand and Trine Bjøro

Epidermal growth factor (EGF) stimulated the prolactin (PRL) synthesis and release from the GH4C1 cells in a dose-dependent manner. The ED50 was between 10−11 and 10−10 mol/l. The maximal effect was obtained at 10−9 mol/l EGF for the release, and 10−8 mol/l EGF for the synthesis. EGF stimulated the release of PRL from cell perfusion columns after a lag period of about 30 s. The maximal secretion of PRL occurred about 60 s after the start of stimulation. The PRL secretion declined to basal levels within 2 min. The EGF-stimulated PRL release was additive to the secretion evoked by thyrotropin-releasing hormone (TRH) and vasoactive intestinal peptide (VIP). An instantaneous increase in the intracellular concentration of free calcium, [Ca2+]i, of the GH4C1 cells was observed after the administration of EGF. EGF modified neither the basal nor the TRH-stimulated inositoltrisphosphate production in the GH4C1 cells, and EGF did not show any effect on the cyclic adenosine monophosphate production of these cells.