Meeting Abstract
P2.142 Wednesday, Jan. 5 Compensatory Gonadal Hypertrophy in the Marsh Rice Rat (Oryzomys palustris) EDMONDS, Kent E; Indiana University Southeast kedmonds@ius.edu
Compensatory gonadal hypertrophy (CGH) is a phenomenon in which the surgical removal of one gonad results in a significant increase in the size of the remaining gonad relative to gonadally-intact animals. The marsh rice rat is a reproductively photoperiodic species that responds to long photoperiods with enhanced reproductive activity and to short photoperiods with inhibited reproductive activity. CGH was examined in male and female rice rats of various ages to determine if the phenomenon occurs and is age-specific. Juvenile male and female rice rats housed on 14L:10D were weaned at 3 weeks of age and sham unilaterally castrated or unilaterally ovariectomized (sham ULC or sham ULO) or ULC or ULO. At 8 weeks of age, pups were weighed and sacrificed. The right testis or ovary, seminal vesicles, right epididymis, uterus, spleen, and Harderian glands were removed and weighed. Significant CGH occurred in males, but not females. No other endpoints measured were affected in either sex. To examine whether CGH could be unmasked in juvenile females, animals were housed on 12L:12D from weaning and sham ULO or ULO and given subcutaneous melatonin implants (20 mm total). Significant CGH occurred in ULO and melatonin-implanted females compared to controls, suggesting CGH can be unmasked in juvenile females under some experimental conditions. In adults, males did not exhibit CGH five weeks post-surgery, but females did. Again, no other endpoints measured were significantly affected. The effect of melatonin implants on ULO-induced CGH in adult females is currently being investigated. Taken together, these results show that CGH is dependent upon the age and sex of the individuals. It is unknown why juvenile males and adult females undergo significant CGH, while juvenile females and adult males fail to exhibit CGH. (Supported by funds from IUS to KEE)
