lhrh--n-ac-2-nal(1)-4-cl-phe(2)-trp(3)-hci(6)-alanh2(10)- and iturelix

We report here the biological characterization of azaline B, a new gonadotropin releasing hormone (GnRH) receptor antagonist, with the following amino acid sequence: [Ac-D-Nal1, D-Cpa2, D-Pal3, Aph5(atz), D-Aph6(atz), Ilys8, D-Ala10]-GnRH. Azaline B was shown to suppress several reproductive processes in rats including ovulation, and had very low anaphylactoid activity compared with other GnRH antagonists. Azaline B inhibited histrelin (a GnRH agonist)-mediated follicle stimulating hormone (FSH) and luteinizing hormone (LH) release from cultured rat pituitary cells. Three antagonists ([Nal-Glu]-GnRH, [Nal-Lys]-GnRH ("antide"), and azaline B) inhibited 0.1 nM histrelin-mediated gonadotropin release to baseline levels with EC50 values of approximately 0.6 nM. Azaline B, when injected s.c. into rats on the afternoon of proestrus, was more potent at inhibiting ovulation than either [Nal-Glu]-GnRH or [Nal-Lys]-GnRH. The relative order of antiovulatory potencies of the three antagonists was azaline B > [Nal-Glu]-GnRH > [Nal-Lys]-GnRH. Similar azaline B potency was shown by its ability to suppress gonadotropin levels in castrated rats. The improved selectivity of azaline B was demonstrated when it was compared with other GnRH antagonists in the cutaneous anaphylactoid assay (local wheal response) in rats. Results with azaline B were not significantly different from results with vehicle in this assay. [Nal-Glu]-GnRH was more than twice as potent as [Nal-Lys]-GnRH in stimulating a wheal response. Furthermore, the maximal wheal response produced by azaline B was only 0.6 times that of [Nal-Lys]-GnRH, currently one of the most selective antagonists identified. Finally, both azaline B and [Nal-Lys]-GnRH were much less potent than [Nal-Glu]-GnRH in the guinea pig cardiopulmonary anaphylactoid assay after i.v. administration. These data show that azaline B is a potent and selective GnRH receptor antagonist with little or no anaphylactoid activity in animal models, and therefore has potential for use in the treatment of many reproductive endocrine disorders, as well as for use as a contraceptive.

Topics: Amino Acid Sequence; Anaphylaxis; Animals; Female; Follicle Stimulating Hormone; Gonadotropin-Releasing Hormone; Guinea Pigs; Luteinizing Hormone; Molecular Sequence Data; Oligopeptides; Ovariectomy; Ovulation; Pituitary Gland; Rats; Rats, Wistar; Receptors, LHRH

Recent studies have suggested that hypothalamic and pituitary hormones may directly influence the immune system. One such hormone with immunomodulatory properties is GnRH. We hypothesized that GnRH and/or the gonadotropins might alter the severity of autoimmune disease through mechanisms distinct from their effects on gonadal hormones. This possibility was tested in a murine model of lupus. We assessed disease severity over time in intact and castrated, male and female, lupus-prone (SWR x NZB) F1 hybrid mice during treatment with GnRH agonist, GnRH antagonist, or vehicle. Compared to vehicle administration, GnRH antagonist administration significantly decreased total serum immunoglobulin G and anti-DNA antibodies in castrated male and female mice and significantly improved survival. In contrast, GnRH agonist administration exerted reciprocal effects in castrated mice, leading to early increases in serum anti-DNA and total immunoglobulin G levels. We conclude that GnRH and/or the gonadotropins can modify the expression of murine lupus independently of their regulation of gonadal steroid secretion.

Topics: Animals; Antibodies, Antinuclear; Estradiol; Female; Flow Cytometry; Gonadotropin-Releasing Hormone; Hematuria; Immunoglobulin G; Lupus Erythematosus, Systemic; Luteinizing Hormone; Male; Mice; Mice, Mutant Strains; Oligopeptides; Orchiectomy; Ovariectomy; Proteinuria

The dose-response effects of a single administration of Nal-Lys-GnRHant (antagonist) on serum LH and FSH concentrations were compared to the effects of Nal-Glu-GnRHant in monkeys. Twenty ovariectomized monkeys were divided into four sc treatment groups: a) 1.0 mg/kg Nal-Glu-GnRHant; or Nal-Lys-GnRHant at b) 0.3; c) 1.0; d) 3.0 mg/kg. Each monkey received vehicle (propylene glycol/water, 1:1) on day 0, followed by an antagonist preparation on day 11. Serum LH and FSH were measured by RIA; serum LH was also measured by in vitro bioassay. The short-term effects were similar among the four treatment groups. Typically, serum LH declined (p less than 0.05) within 4 to 8 h, achieving maximal reduction by 24 h. Serum FSH levels declined more slowly, but were significantly reduced by 24 h (p less than 0.05). Recovery during the study interval to pretreatment control values occurred in only two groups: a) Nal-Glu-GnRHant (1.0 mg/kg) by day 4 post-treatment and b) Nal-Lys-GnRHant (0.3 mg/kg) by day 2 post-treatment. Monkeys receiving 1.0 or 3.0 mg/kg Nal-Lys-GnRHant had a prolonged inhibition of serum LH and FSH levels. In all animals, serum FSH and LH returned to control levels within 2 months. The duration of gonadotropin inhibition was also prolonged when the Nal-Lys-GnRHant was administered iv. In contrast, Nal-Glu-GnRHant reduced serum LH and FSH for 3 days or less in all monkeys. The serum bioassayable LH levels paralleled those of immunoassayable LH. The prolonged inhibition of gonadotropin secretion following Nal-Lys-GnRHant distinguishes its action from those of previous GnRH antagonists and make this compound of great interest for clinical investigations.

Topics: Animals; Dose-Response Relationship, Drug; Female; Follicle Stimulating Hormone; Gonadotropin-Releasing Hormone; Injections, Intravenous; Injections, Subcutaneous; Luteinizing Hormone; Macaca fascicularis; Oligopeptides; Ovariectomy