Porcine Hypothalamic Aromatase Cytochrome P450: Isoform Characterization, Sex-Dependent Activity, Regional Expression, and Regulation by Enzyme Inhibition in Neonatal Boars1

Abstract

Domestic pigs have three CYP19 genes encoding functional paralogues of the enzyme aromatase cytochrome P450 (P450arom) that are expressed in the gonads, placenta, and preimplantation blastocyst. All catalyze estrogen synthesis, but the gonadal-type enzyme is unique in also synthesizing a nonaromatizable biopotent testosterone metabolite, 1OH-testosterone (1OH-T). P450arom is expressed in the vertebrate brain, is higher in males than females, but has not been investigated in pigs, to our knowledge. Therefore, these studies defined which of the porcine CYP19 genes was expressed, and at what level, in adult male and female hypothalamus. Regional expression was examined in mature boars, and regulation of P450arom expression in neonatal boars was investigated by inhibition of P450arom with letrozole, which is known to reprogram testicular expression. Pig hypothalami expressed the gonadal form of P450arom (redesignated the "gonadal/hypothalamic" porcine CYP19 gene and paralogue) based on functional analysis confirmed by cloning and sequencing transcripts. Hypothalamic tissue synthesized 1OH-T and was sensitive to the selective P450arom inhibitor etomidate. Levels were 4-fold higher in male than female hypothalami, with expression in the medial preoptic area and lateral borders of the ventromedial hypothalamus of boars. In vivo, letrozole-treated neonates had increased aromatase activity in hypothalami but decreased activity in testes. Therefore, although the same CYP19 gene is expressed in both tissues, expression is regulated differently in the hypothalamus than testis. These investigations, the first such studies in pig brain to our knowledge, demonstrate unusual aspects of P450arom expression and regulation in the hypothalamus, offering promise of gaining better insight into roles of P450arom in reproductive function.

Stimulation of Sertoli cell proliferation: defining the response interval to an inhibitor of estrogen synthesis in the boar

“…Testes were weighed, one sample was fixed in 4% paraformaldehyde for determination of Sertoli cell density, and a second sample was frozen on dry ice for subsequent determination of testicular steroid levels. Hypothalamic and testicular aromatase activities were previously reported for these boars (Corbin et al 2009). The second experiment further investigated the initial phase of the first wave of Sertoli cell proliferation.…”

“…Testicular tissue levels of testosterone Values represent least squares means for four boars except the 1-, 3-, and 5-week value, which is the mean of three boars from three different litters. (Corbin et al 2009); 400 ml sample volumes extracted with ether to lower assay detection limit to 5 pg/ml but values in some samples were lower. Values previously reported (Corbin et al 2009).…”

“…(Corbin et al 2009); 400 ml sample volumes extracted with ether to lower assay detection limit to 5 pg/ml but values in some samples were lower. Values previously reported (Corbin et al 2009). c Testes weight for boars treated with letrozole at 1, 3, and 5 weeks of age differed from littermates treated with vehicle, P!0.05.…”

Sexually dimorphic transcription of estrogen receptors in cod gonads throughout a reproductive cycle

“…It is encoded by a single gene in mammals, with exception of the domestic pig and other suiformes, which have multiple cyp19 genes (Corbin et al 2009). In contrast, teleosts have two cyp19 genes: cyp19a1a is preferentially expressed in ovaries, whereas cyp19a1b is found predominantly in brain (Tchoudakova & Callard 1998).…”

Effect of L-carnitine on Lead-induced Infertility in Female Rats

“…There are three isomers of CYP19 gene CYP19a1(gonads), CYP19a2(brain) [27,28] and CYP19a3 (Sus scrofa (Pig)) [27,28].…”