Steroidogenic gene expression following d-aspartate treatment in frog testis

Abstract

Previous studies have provided evidence that d-Asp plays a role in steroid-mediated reproductive biology in amphibians, reptiles, birds and mammals. To examine the molecular involvement of d-Asp on steroidogenic pathway regulation, we analysed the expression of StAR, P450 aromatase and 5αRed2 mRNAs in Pelophylax esculentus testis, either in relation to the reproductive cycle or d-Asp treatment. Basal StAR mRNA levels, as well as d-Asp and testosterone concentrations, were higher in reproductive than in post-reproductive frogs. d-Asp treatment increased StAR mRNA expression and immunolocalisation in both the reproductive and post-reproductive periods. In control testis, aromatase mRNA levels were higher in the post-reproductive period, but following d-Asp administration, they increased only in the reproductive period. The level of 5αRed2 mRNA was higher in reproductive frogs than in post-reproductive frogs, and it increased after d-Asp treatment only in the post-reproductive phase. Our results suggest that, in P. esculentus testis, d-Asp increases StAR mRNA in both periods, and P450 aromatase and 5αRed2 mRNAs at different points during the reproductive cycle.