The effect of aromatase inhibitor on basal and testosterone-supplemented estradiol secretion by Leydig cells in vitro

The effect of increasing concentrations of aromatase inhibitor CGS 16949 A on LH- and testosterone-supplemented estradiol secretion by Leydig cells was studied. Leydig cells were obtained from mice at different ages from 15- to 140-day-old. They were either incubated for 6 hrs with LH and/or testosterone (LH/testosterone-supplemented cultures), or as the control cultures. Aromatase inhibitor was added for further 18h. After 24-h incubation period estradiol secretion was radioimmunologically examined. Leydig cell aromatase activity appeared to depend on the age of the donor mice, being higher in mature than in juvenile animals. Furthermore, the Leydig cells from 30-day-old mice seemed to reveal such an increasing aromatase activity resulting in the higher level of synthetized estradiol. Aromatase inhibitor influenced the Leydig cell functions in a dose-dependent manner (60-70-day-old mice), or independently of the dose used. This supports the hypothesis that Leydig cells from the testes of mature mice are the main site of an active aromatase.