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D Gourdji

Publications and source records attributed to D Gourdji.

61 records · Page 4Linked to original sources
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Dopamine inhibition of action potentials in a prolactin secreting cell line is modulated by oestrogen.

Secretory activity of the anterior pituitary gland is regulated by the brain through stimulatory and inhibitory substances released from nerve endings in the median eminence of the hypothalamus and carried by the adenohypophysial portal blood system to their respective target cells. These hypothalamic influences are modulated by the feedback action of peripheral hormones. Prolactin (PRL) secreting cells are, at least partially, under the stimulatory influence of thyrotropin releasing hromone (TRH) and of oestrogens. However, they are mainly controlled by inhibitory substances among which dopamine (DA) is one of the most potent in vivo as well as in vitro. The inhibitory effect of DA is reversed by oestrogen in vitro. The mechanism by which these factors interact on their target cells is poorly understood. The recent discovery that anterior pituitary cells are excitable and that they are able to generate Ca2+-dependent action potentials has led to the suggestion that these effects are involved in a stimulus-secretion coupling at the membrane level. In this paper, we report that DA inhibits both the spontaneous and TRH-induced action potentials in clonal PRL pituitary cells. In addition, oestradiol-17 beta is able to reverse the inhibitory effect of DA.

Action Potentials↗
PubMedDate not supplied

[Radio-receptor assay for thyrotropin releasing hormone (author's transl)].

The high affinity receptor for TRH of a rat pituitary GH3 strain in culture (Km: 4 X 10(-9) M) was found suitable to design a radio-receptor assay for TRH. Attached GH3 cells were incubated for 30 min at 37 degrees C in presence of a tracer amount of 3H-TRH (200 pg/ml, 0.54 nM) and increasing quantities of cold synthetic TRH. After extensive washings, the radioactivity associated with the cells was counted, and the log-logit transformation was applied to the results expressed as % binding (100%: binding in absence of unlabelled TRH). The standard curve is linear between 200 pg/ml and 5 ng/ml TRH. Hypothalamic or thyroid hormones were tested for their competitive effect with 3H-TRH towards the GH3 cells receptor. None of them interfered. TRH analogs were also assayed for their competition with TRH towards the receptor. Only compounds methylated on Prolineamide or Histidine could compete with TRH, but these derivatives have never been shown to occur in vivo. Because of this high specificity, we applied this radioreceptor assay to biological samples, once extracted by acidic methanol and purified by CMC column (following a technics designed by K Bauer, Berlin).

Animals↗
PubMedDate not supplied

[Fate of thyrotropin releasing hormone after binding to rat prolactin secreting cells (GH3 line). Evidence for releasing of unmodified [3H]-TRH (author'r transl)].

It was previously shown that after a 30 min. incubation with [3H]-TRH intact GH3 cells have already performed their optimal precocious biological response to TRH (i.e increase of prolactin release) and that chemically unmodified ( greater than or equal to 93%) [3H]-TRH entered the cells and remained associated to them. The present work demonstrates that such cells spontaneously release a radioactive material ([3H]RM) when post-incubated at 37 degrees C. The binding to GH3 cells (time course and competition with unlabelled TRH) as well as the biological effect on prolactin release and the electrophoretic mobility of the [3H]-RM released in one hour were compared to those of [3H]-TRH. According to those criteria [3H]-RM is undistinguishable from [3H]-TRH at 90%. Our data, therefore, support the hypothesis of a continuous flow of TRH molecules on both sides of the plasma membrane during TRH-GH3 cells interaction.

Animals↗