Endocrinological studies on TAP-144-SR, a sustained-release formulation of a potent GnRH agonist (D-Leu6-[des-Gly10-NH2]-GnRH ethylamide), in male rats

K. Sudo*, T. MAsaki, K. Shiota, M. Kawase, T. Fujita

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


The paradoxical effects of TAP-144-SR, a biodegradable sustained-release formulation of a potent GnRH agonist (TAP-144, leuprolide acetate) were evaluated in male rats by comparing its potency with that of TAP-144 solution. A single sc injection of TAP-144-SR (equivalent to 0.1 mg/kg/day as TAP-144), prepared by encapsulating the agonist in microcapsules of copoly (DL-lactic/glycolic acid), suppressed serum levels of androgens, and the levels remained suppressed for 4 weeks. The potency of the paradoxical effects of TAP-144-SR was evaluated 4 weeks after treatment by comparing it with that of TAP-144 solution administered daily for 4 weeks. Both daily injections of TAP-144 solution and a single injection of TAP-144-SR (equivalent to 0.02, 0.2 or 2 mg/kg/day as TAP-144) decreased the weight of the testes, prostates and seminal vesicles in a dose-dependent manner in a 4-week assay in male rats. TAPA-144-SR was more effective than TAP-144 solution in reducing these organ weights. Serum and pituitary concentrations of LH and FSH and serum testosterone levels were also lower in TAP-144-SR-treated than in TAP-144 solution-treated rats. These results indicate that the paradoxical effects were more extensive upon TAP-144-SR treatment, suggesting that maintaining constant serum TAP-144 levels results in more extensive desensitization of the pituitary and testes. These results also suggest advantages of TAP-144-SR over TAP-144 solution in both efficacy and convenience as an anti-prostatic tumor agent.

Original languageEnglish
Pages (from-to)685-693
Number of pages9
JournalEndocrinologia Japonica
Issue number5
Publication statusPublished - 1990
Externally publishedYes

ASJC Scopus subject areas

  • Endocrinology


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