Production of transgenic rats using young Sprague-Dawley females treated with PMSG and hCG

The aim of this study was to examine the effects of gonadotrophin treatment s on estrus synchronization and superovulation in young Sprague-Dawley (SD) rats that had not yet exhibited defined estrus cycles (5 to 7 weeks old), and to produce transgenic rats using these females as embryo donors and rec ipients. In Experiment 1, female rats were injected with PMSG and hCG (12.5 , 25, 50 and 100 IU/kg each) and were mated with stud males. The reproducti ve performance of young rats were highest when PMSG and hCG at doses of 25 IU/kg each were injected (delivery rate 87.5%, nursing rate 92.9%). In Expe riment 2, female rats were injected with PMSG and hCG (100, 150 and 300 IU/ kg each) to induce superovulation. More eggs were recovered from the rats i njected with PMSG and hCG at 150 and 300 IU/kg than from those treated with 100 IU/kg (33.4 and 41.3 vs. 13.3 eggs per female, respectively, p <0.05). In Experiment 3, pronuclear-stage zygotes from 150 IU/kg PMSG/hCG-treated rats were used for microinjection of the fusion gene of bovine alpha S1-cas ein gene promoter and human growth hormone gene (2.8 kb), and the microinje cted zygotes were transferred into the oviduct ampullae of the 25 IU/kg PMS G/hCG-treated rats. Seventeen transgenic rats were obtained from the 334 DN A-injected zygotes (5.1%). These results indicate that recipients and embry o donors for the production of transgenic rats can be prepared by the appro priate PMSG and hCG treatments of young SD rats, regardless of their estrus stages.