Reversible increase in energy deposition following castration induced by a gonadotropin releasing hormone agonist

The effects on energy balance of a potent gonadotropin releasing hormone (GnRH) agonist, have been investigated in rats. Female rats initially weighing 180 g were divided into three groups. One group of rats underwent a bilateral ovariectomy whereas the two remaining groups were sham-operated. Rats in one of the two sham-operated groups were treated with Buserelin which was administrated by means of miniosmotic pumps. The remaining rats were implanted with minipumps that delivered saline. After 28 days of treatment, half of the rats in each group were killed by decapitation whereas the remaining animals had their pumps removed so that the Buserelin treatment stopped. The post-treatment lasted 28 days after which period, rats were killed. Body weight and food intake were measured over every 2 or 3 day periods. Carcasses were analyzed for their contents in protein, fat and energy. During the treatment period, rats that were ovariectomized and those treated with Buserelin increased their food intakes and energy depositions. The increase in energy deposition reflected an increase not only in fat but also in protein deposition. During the post-treatment period, metabolizable energy intake of rats that were administered Buserelin returned to the levels of placebo-treated rats. Twenty-eight days post-treatment, the carcass energy contents of the Buserelin-treated rats were no longer different from those of placebo-treated rats. In conclusion, Buserelin induces an increase in energy deposition that is readily reversed upon cessation of the treatment.