Silicone implants for delivery of estradiol-17β and 11-ketotestosterone to red seabream Pagrus major

To develop effective methods for delivering steroid hormones to red seabream, we investigated the utility of dimethyl sulfoxide (DMSO) as a solvent for steroid hormones by examining the in vitro and in vivo release of estradiol-17β (E2) and 11-ketotestosterone (11-KT) from silicone capsules. In vitro E2 and 11-KT release rates from capsules containing steroid hormones in castor oil were proportional to the concentration of steroids within capsules. Increasing the proportion of DMSO to castor oil increased sex steroid hormone release from the capsules. The in vivo implantation of a single capsule containing 400 μg of E2 in 50% DMSO or 11-KT in 25% DMSO effectively increased serum levels of each steroid hormone in juvenile red seabream for a month. These results demonstrate that use of silicone capsules containing steroids in DMSO provides a useful method for delivering controlled and easily manipulated physiological doses of E2 and 11-KT to large fish such as red seabream.