Meeting Abstract

P1.39  Wednesday, Jan. 4  Hormonal and Metabolic Regulation of Compensatory Testicular Hypertrophy in the Marsh Rice Rat (Oryzomys palustris) EDMONDS, K.E.; Indiana University Southeast

Compensatory testicular hypertrophy (CTH) is a phenomenon in which the surgical removal of one testis results in a significant increase in the size of the remaining testis relative to control animals. CTH was examined in juvenile male rice rats to determine if its regulation is subject to hormonal and metabolic manipulation. Juvenile males housed on 14L:10D were weaned at 3 weeks of age and sham unilaterally castrated (sham ULC) or ULC. Rice rats were implanted subcutaneously with 15 mm capsules that were empty (E; control) or contained estradiol (E2), dihydrotestosterone (DHT), or corticosterone (C). At 8 weeks of age, pups were weighed and sacrificed. The right testis, seminal vesicles (SV), right epididymis, spleen, and Harderian glands (HG) were removed and weighed. Significant CTH occurred in E, DHT, and C males. E2 dramatically inhibited body mass, the HG, and all reproductive development. Interestingly, E2 increased spleen mass. DHT also increased SV and HG mass. To examine whether CTH could be stimulated on a short photoperiod, animals were transferred from 14L:10D to 13L:11D at weaning and sham ULC or ULC and chronically provided sulpiride (a dopamine antagonist hypothesized to elevate endogenous prolactin levels) in the drinking water. There was a significant effect of sulpiride on the right testis in ULC males, suggesting that CTH can be altered in males housed on a short photoperiod. Other endpoints measured were not dramatically affected. Lastly, in ULC males injected daily with 2-deoxy-D-glucose (2-DG), an inhibitor of intracellular glucose utilization, CTH was inhibited at three weeks post-surgery. The only other endpoint significantly affected was the spleen which was reduced in size in 2-DG animals. Taken together, these results show that CTH is dependent upon the hormonal and metabolic environment in rice rats. (Supported by the Indiana Academy of Science)