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Gonadotropin-releasing hormone (GnRH) is briefly discussed. Luteinizing hormone (LH) secretory response to GnRH in vitro was obtained even in calcium-free medium. It is concluded that calcium is not an absolute requirement for the GnRH-stimulated LH release. In the absence of calcium, however, there was no response of LH to nonspecific stimuli such as(More)
Phenytoin exposure in utero results in permanent alterations of the hypothalamic-pituitary-thyroid axis in the rat. The DPH exposed animals have decreased weight gain, thyroxine and triiodothyronine concentrations. In addition, they have blunted thyroid-stimulating hormone responses to thyrotropin-releasing hormone, propylthiouracil challenge or(More)
[125I]-(GnRH) concentration dependence binding curves using isolated bovine anterior pituitary plasma membranes, intact and solubilized, and purified GnRH receptor protein, are compared. In all instances the concentration dependence binding curves had a stepwise character here interpreted as multisigmoid, with several steep increases and plateaus. These(More)
Specific binding of a fully biologically active 125I-gonadotrophin releasing hormone (GnRH) to isolated anterior pituitary cells is time dependent, saturable and the concentration dependent binding curves exhibit positive cooperativity. Binding to intact or solubilized plasma membranes and an affinity purified GnRH receptor protein reveals in all instances(More)
Functioning gonadotropin-releasing hormone (GnRH) receptor is visualized as an aggregate of identical subunits (not all always functional) with the aggregate usually transformed into at least four successive structurally distinct receptor assemblies. Receptor protein, hormone molecule(s), and carrier(s) are main components of each functional subunit. During(More)
LH release from the anterior pituitary was studied by the method of an in vitro superfusion of bovine anterior pituitary tissue slices. LH release was stimulated by increased potassium concentration (23 and 59 mM) and by synthetic GnRH (1 and 4 ng/ml). While the potassium effect was completely dependent on extracellular calcium, that of GnRH was only(More)
Synthetic gonadotropin-releasing hormone (GnRH) was monoiodinated at a high specific radioactivity with 125I. The iodinated hormone retained full biological activity as assessed by the release of luteinizing hormone in vitro from bovine anterior pituitary tissue slices. Specific binding of 125I-labeled gonadotropin-releasing hormone of high affinity and low(More)
In a hormonal system stimulated by one of the known hypothalamic peptides, gonadotropin releasing hormone (GnRH), the biological response seen, when physiologically called for, may be positively co-operative, showing as well the expected dynamics due to a singular or continuing stimulus. Mediation is by a receptor protein which in purified form shows(More)
It has been reported that phenobarbital (PB) increases the peripheral clearance of T4 and T3 and decreases serum T4 and T3 concentrations in the rat, but serum TSH remains unchanged. To explore a possible direct effect of PB on TSH secretion at the hypothalamic-pituitary level, adult male rats were given PB 100 mg/kg or vehicle IP for 10 days. No difference(More)