title: Prolonged suppression of plasma LH levels in male rats after a single injection of an LH-RH agonist in poly(DL-lactide-co-glycolide) microcapsules.
abstract: The authors have examined the effects of a subcutaneous injection of the LH-RH agonist D-Trp6-LH-RH formulated in biodegradable poly(DL-lactide-co-glycolide) microcapsules on plasma levels of D-Trp6LH-RH, LH, and PRL in adult, gonadectomized male rats. Immunoreactive D-Trp6-LH-RH was detectable in the plasma of these animals at 1, 2, 3, and 4 weeks after injection. LH concentrations were greatly reduced 1 week after administering the D-Trp6-LH-RH microcapsule, continued to decrease during the following week, and remained suppressed until the end of the study, 6 weeks after the injection. Plasma PRL levels appeared elevated 1 to 2 weeks after the injection and suppressed thereafter, but these effects were significant only in animals rendered hyperprolactinemic by transplantation of an isologous pituitary under the renal capsule. These results demonstrate that an LH-RH agonist formulated in biodegradable microcapsules and administered as a subcutaneous injection can exert marked biologic effects in rats for at least 6 weeks. These findings also suggest that prolonged exposure to an LH-RH agonist may first produce stimulation, followed by an inhibition of PRL release from both in situ and ectopic pituitaries.
authors.forename: R H
authors.initials: RH
authors.lastname: Asch
authors.forename: F J
authors.initials: FJ
authors.lastname: Rojas
authors.forename: A
authors.initials: A
authors.lastname: Bartke
authors.forename: A V
authors.initials: AV
authors.lastname: Schally
authors.forename: T R
authors.initials: TR
authors.lastname: Tice
authors.forename: H G
authors.initials: HG
authors.lastname: Klemcke
authors.forename: T M
authors.initials: TM
authors.lastname: Siler-Khodr
authors.forename: R E
authors.initials: RE
authors.lastname: Bray
authors.forename: M P
authors.initials: MP
authors.lastname: Hogan
mesh_terms: D000818:Animals; D001673:Biodegradation, Environmental; D002214:Capsules; D002369:Castration; D003692:Delayed-Action Preparations; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000097:blood / Q000494:pharmacology / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D011098:Polyglactin 910; D011388:Prolactin / Q000097:blood; D051381:Rats; D011916:Rats, Inbred F344; D017329:Triptorelin Pamoate
chemical_list: D002214:Capsules; D003692:Delayed-Action Preparations; D017329:Triptorelin Pamoate; D007987:Gonadotropin-Releasing Hormone; D011098:Polyglactin 910; D011388:Prolactin; D007986:Luteinizing Hormone