The Presence of Aromatase mRNA and Protein in Ovine Mammary Fat Pad and Possible Effect of Birth Status on its Abundance
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Date
2012-06
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The Ohio State University
Abstract
Aromatase is an enzyme that is important to concentrations of sex hormone in both developing and mature animals. It converts the male sex-hormone testosterone to estrogen, the female sex-hormone. One of the many functions of estrogen is to stimulate the growth of mammary glands of prepubertal animals. A previous study conducted in the Animal Sciences Department at The Ohio State University provided detailed statistics about mammary gland and carcass traits of female lambs born with a twin. It seems that growth of mammary glands, specifically the fatty portion of the tissue, is influenced by the sex of the twin that is gestated with a female lamb. Female lambs with a male twin had 30% more fatty tissue in mammary glands than female lambs with a female twin. Another difference observed was that females with a male twin have less body fat than females with a female twin. Fat is one source of estrogen, so aromatase presence in the fatty tissue of female sheep mammary glands may be of developmental significance. We hypothesized that aromatase is present in the fatty tissue, and we further rationalized that the relative amount would be different depending on if female lambs were gestated with a female lamb or a male lamb. To test this, mammary tissue from 8 sets of female-female twin pairs (FF; n = 16) and 11 ewe lambs gestated with a male (FM; n = 11) was obtained and subjected to quantitative reverse transcriptase PCR and immunohistochemistry for the aromatase gene and protein, respectively. The aromatase gene was expressed in mammary parenchyma at low levels and was not different due to twin status (P = 0.267); aromatase gene in the fatty portion was below the limit of detection for our assay. Aromatase was found through antibody staining to be primarily located in mammary epithelial cells in the parenchyma, and was found sparsely in the mammary fat pad. Importantly, we demonstrated aromatase at both the gene and protein levels in ewe lambs, which is a novel finding. This perhaps suggests that aromatase is important for prepubertal mammary growth, though not in the manner we originally hypothesized.
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ovine, aromatase, parenchyma