DECONTAMINATION OF RAT EMBRYOS AND TRANSFER TO SPECIFIC PATHOGEN-FREERECIPIENTS FOR THE PRODUCTION OF A BREEDING COLONY

When animals are introduced to a specific pathogen-free (SPF) facility , care must be taken to avoid the possibility of disease transmission to the local colony. This study investigated the application of a comb ination of reproductive biotechnologies to establish a new disease-fre e colony of two rat strains, DarkAgouti(DA/Pit) and Wistar Furth(WF/Pi t), from a stock known to be chronically infected with the following p athogens: Myco-plasma pulmonis, Kilham's rat virus, sialodacryoadeniti s/coronavirus, and reovirus type 3. To eliminate the pathogens and opt imize the use of animals, superovulation, embryo washing and trypsiniz ation, and embryo transfer were used. Donors (DA/Pit and WF/Pit) were treated as follows: the mature females were synchronized by subcutaneo us (s.c.) injection with 40 mu g luteinizing hormone-releasing hormone agonist/animal on day -4. All immature and mature females were induce d to superovulate by continuous s.c. infusion with a commercial porcin e follicle-stimulating hormone (FSH) preparation (3.4 or 6.8 mg NIH-FS H-P1 units per day,respectively), beginning on the morning of day -2. On the afternoon of day 0, the animals received 30 IU human chorionic gonadotropin injected intraperitoneally and mated. From a total of 213 ova flushed from the oviducts of 16 programmed donors, 195 transferra ble two-cell embryos were recovered. Two outbred strains of SPF rats, Long-Evans (LE) and Wistar (W), were used as recipients. These mature females (LE and W) were synchronized by using luteinizing hormone-rele asing hormone agonist as described and made pseudopregnant by cervical stimulation. Two-cell embryos (DA/Pit and WF/Pit) were washed and try psinized, then transferred to the oviducts of the pseudopregnant recip ients (LE and W). From a total of 195 embryos transferred, 57 pups wer e born (29.2% of embryos transferred.) All offspring tested negative f or the viruses infecting the donors as long as they were kept under st rict quarantine. The combination of those three techniques provides an efficient alternative to the traditional derivation by caesarean sect ion.