Responsiveness of rabbits to superovulation treatment by a single injection of follicle-stimulating hormone with aluminum hydroxide gel

Aluminum hydroxide gel (Al-gel), which is used as an adjuvant, can absorb macromolecules. We investigated the applicability of Al-gel to the sustained release of follicle-stimulating hormone (FSH) as a simplified method of superovulation (SOV) in rabbits. The responsiveness of rabbits to SOV by a single injection of FSH dissolved in Al-gel suspension (3.2 mg Al/ml) and in 10% (w/v) polyvinylpyrrolidone (PVP), and by multiple injections of FSH in saline was examined. The numbers of total and fertilized eggs recovered from rabbits treated with FSH in Al-gel (40.5 and 26.3, respectively) were similar to multiple injections (47.4 and 28.6, respectively) and were significantly greater (P < 0.05) than single injection of FSH with PVP (17.3 and 11.5, respectively). We also compared the plasma FSH levels of rabbits which were induced SOV by multiple or a single injection of Al-gel. Al-gel provided sustained release of FSH to the blood stream at a high enough dose for SOV. Moreover, the developmental competence of the pups of DNA-injected embryos from rabbits treated with a single injection of FSH mixed with Al-gel (18%) was similar to that of DNA-injected embryos, recovered from rabbits treated with FSH dissolved in saline (21%). Two transgenic pups were obtained from embryos recovered from rabbits by a single injection of FSH with Al-gel. These results indicate that a single injection of FSH with Al-gel is an effective method for SOV of rabbit and that this technique is applicable to research requiring large numbers of rabbit embryos such as the production of transgenic rabbits.