Multiple Forms of Aromatase in Suiformes: Tissue Distribution, Regulation, and Functional Significance

Pigs have three CYP19 genes encoding functional paralogues of aromatase cytochrome P450 expressed tissue specifically in the gonads/hypothalamus, placenta, and preimplantation blastocyst. Gene duplication is predicted to have relaxed selection pressure and allowed evolution of enzyme function. All isozymes catalyze estrogen synthesis. However, the "gonadal/ hypothalamic" form (ghP450arom) is unique among mammalian aromatases in also synthesizing a nonaromatizable, biopotent testosterone metabolite, 1OH-testosterone (1OH-T) that is hypothesized to have promoted increased ovulation rate and litter size. High ghP450arom expression in porcine testis facilitates study of differential regulation in hypothalamus and gonads that is not possible in other species. These, the first such studies in pig brain, demonstrate unusual aspects of P450arom expression and regulation in the hypothalamus, offering promise of gaining better insight into roles of P450arom in reproductive function.