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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)
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)
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)
Gonadotropin releasing hormone receptor protein (GnRH.RP) purified to homogeneity has several binding sites for its effector hormone, as evidenced from the concentration dependence binding curve. Binding of a fully biologically active iodinated GnRH decreased (P less than 0.001) by pretreatment of immobilized receptor protein with physiological(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)
Serum luteinizing hormone (LH) concentration after exposure to gonadotropin-releasing hormone (GnRH) indicates that an instantaneous increase occurs in the rate of release of LH directly from the anterior pituitary, as measured dynamically during superfusion in vitro. On the other hand, estradiol-17 beta (E2) alone shows no such instantaneous effect on LH(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)