Endocrine Abstracts

Objective: Aromatase, the key enzyme involved in estrogen synthesis, is expressed in a variety of cells, including peripheral blood leukocytes (PBLs), and tissues. The systematic study of aromatase expression and activity in different tissues in the human and other primates, however, is difficult and still missing. Although is not really known, aromatase expression in PBLs could be used as parameter of aromatase expression/activity making PBLs a potential alternative for other tissues. The aim of this study was to characterize the expression of the CYP19A1 gene in several tissues of male cynomolgus monkeys and to compare the expression levels with those in PBLs.

Design: CYP19A1 RNA and protein were measured in PBLs, skin fibroblasts, mammary gland, testis, muscle, liver, epididymis and hypothalamus obtained from six hemicastrated male animals aged between 24 and 26 years.

Methods and results: Aromatase RNA measured by real-time PCR was very variable within the individual tissues and was the highest in mammary gland and hypothalamus, (significant vs. PBLs, not vs. other tissues). Conversely, aromatase protein expression by Western Blotting was relatively uniform between animals, with the highest levels in testis and epididymis (significant vs. PBLs). However, no significant correlation between the levels of transcripts and the relative quantity of protein was seen.

Conclusions: Macaca fascicularis CYP19A1 RNA and protein are expressed in all cells and tissues analysed. Lowest aromatase expression levels were seen in PBLs with no correlation with other tissues. We conclude that aromatase expression in PBLs cannot be used as parameter of aromatase expression/activity for other tissues. It is postulated that in these blood cells aromatase produces estrogens with paracrine activity on development and maintenance of the immune system.