Effect of DA-8159, a Selective Phosphodiesterase Type 5 Inhibitor, on Electroretinogram and Retinal Histology in Rabbits

DA-8159, a selective inhibitor of phosphodiesterase type 5, was developed as a new drug for erectile dysfunction. The effect of DA-8159 on the electroretinogram (ERG) and the retinal histopathology were evaluated in rabbits. The ERG was performed prior to, and 1 and 5 hr after DA-8159 (5 to 30 mg/kg) administration. The plasma concentration of DA-8159 was determined at each time point, and retinal microscopic examination was also performed. There was no statistically significant ERG change at any dose or at any time. Though the 30 Hz flicker showed a prolongation of the implicit time at 5 hr after the administration of either DA-8159 15 mg or 30 mg/kg (p<0.05), but concurrent amplitude decreases were not statistically significant. At a dose of 5 mg/kg, no test drug was detected in the blood after either 1 or 5 hr. At either 15 mg/kg or 30 mg/kg, there was a dose-dependent increase in the blood concentration after 1 hr of drug administration, which decreased with time. In light and electron microscopic examinations of the retina, there was no remarkable change at any dose. These results suggest DA-8159 has a low risk potential to the retina, but further evaluation on the visual functions in human is needed.

Effect of IP3 and ryanodine treatments on the development of bovine parthenogenetic and reconstructed embryos

For parthenogenetic activation as a model system of nuclear transfer, microinjection and electroporation as activation treatments in bovine metaphase II oocytes were administered to each of three groups as follows: control group (treatments with Ca2+, Mg2+ -free PBS+100 micro M EGTA), IP3 group (control+25 micro M IP3) and IP3+ ryanodine group (control+25 micro M IP3+10 mM ryanodine). In experiments using microinjection, no significant differences were observed between any of the developmental stages of the electroporation experiment. For electroporation, cleavage rates were significantly higher in the IP3+ryanodine group than in the IP3 or control group (85.6% vs 73.7% or 67.6%, respectively). In the subsequent stages of embryonic development, such as morula and blastocyst formation, the IP3 and ryanodine group exhibited significantly higher rates of morula fomation than the IP3 or control groups (40.6% vs 24.2% or 16.7%, respectively). Similarly, the rate of blastocyst formation in the IP3+ryanodine group was significantly higher than the control group (16.3% vs 6.9%) but did not differ significantly from the IP3 group (16.3% vs 9.5%). In nuclear transfer, activation was performed at 30 hpm by microinjection and elecroporation with 25 micro M IP3+ 10 mM ryanodine followed by 6-DMAP treatment. No significant differences were observed at any stage of embryonic development and none of the embryos activated by electroporation reached either the morula or blastocyst stage. However, 3.8% and 1.9% of embryos activated by microinjection sucessfully developed to the morula and blastocyst stages, respectively. In conclusion, activation treatments using IP3 and ryanodine are able to support the development of bovine parthenogenetic and reconstructed embryos.