Preparation and evaluation of polyanhydride microspheres containing gonadotropin-releasing hormone (GnRH), for inducing ovulation and spermiation in fish

TitlePreparation and evaluation of polyanhydride microspheres containing gonadotropin-releasing hormone (GnRH), for inducing ovulation and spermiation in fish
Publication TypeJournal Article
Year of Publication1995
AuthorsMylonas, CC, Tabata Y, Langer R, Zohar Y
JournalJournal of Controlled Release
Volume35
Issue1
Pages23 - 34
KeywordsAquaculture, Biodegradable microsphere, Gonadotropin-releasing hormone, Polyanhydride, Reproduction
Abstract

We developed a microspheric delivery system for a synthetic analog of gonadotropin-releasing hormone (GnRHa) for inducing ovulation and enhancing spermiation in broodfish which, relative to mammals, are maintained at low temperatures (10-22°C). The microspheres were based on a biodegradable copolymer of fatty acid dimer and sebacic acid (p[FAD-SA]) of a 25:75 molar ratio, and were prepared by a solvent evaporation method, using double emulsion. The GnRH analog [d-Ala6, Pro9NEt]-GnRH was entrapped into the microspheres at 3% loading with 86% (± 5.4) efficiency. The prepared microspheres had a spherical shape, with diameters from 10 to 240 μm. In vitro, GnRHa was released for at least 90 days at 15°C, following an initial release of 8.8% of the total amount. The release during the first 30 days followed first-order kinetics described by the equation GnRHa (μg) = 1.7[day]0.33 (R2=0.99), and zero-order kinetics thereafter, described by the equation GnRHa (μg) = 0.027[day] + 4.5 (R2 = 0.98). Plasma GnRHa levels of microsphere-injected striped bass (Morone saxatilis) remained elevated for at least 8 weeks at 16°C, although the levels dropped dramatically after day 28. Microsphere injection of post-vitellogenic striped bass females and Atlantic salmon (Salmo salar) induced 100% ovulation by day 11 and 15 after treatment, respectively. Similar treatment induced a 4-10-fold increase in sperm production of striped bass males for at least 14 days after treatment and resulted in a 2.5-fold increase of expressible sperm volume of male Atlantic salmon 10 days after treatment. © 1995.

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