Expression and Immunolocalization of Functional Cytochrome P450 Aromatase in Mature Rat Testicular Cells1

Abstract

Aromatase activity has been measured in Leydig cells and Sertoli cells from both immature and mature rats. Cytochrome P450 aromatase (P450arom) has been immunolocalized in germ cells of the rodent, bear, and rooster. Our purpose was to investigate expression of and to immunolocalize P450arom in adult rat testicular cells. After Western blotting with a specific anti-cytochrome P450arom antibody, we demonstrated the presence of a 55-kDa protein in mature rat seminiferous tubules and crude germ cell preparations. Immunoreactive aromatase was detected both in cultured rat Leydig cells and in testis sections (interstitial tissue and elongated spermatids showed positive immunoreactivity for P450arom). We next used reverse transcription-polymerase chain reaction to localize and quantify the P450arom mRNA in the various testicular cells. In rat Leydig cells, the amount of P450arom mRNA was 15 times higher than in Sertoli cells (34.1+/-3.2 to 2.3 +/-0.2 x 10(-3) amol/10(6) cells, respectively). In pachytene spermatocytes, round spermatids, and testicular spermatozoa the P450arom mRNA levels were 38.7+/-8.1, 20.4+/-3.8, and < 1.3 x 10(-3) amol/10(6) cells, respectively. The aromatase activity was 2.5-4 times higher in testicular spermatozoa (8.48+/-1.98 fmol/10(6) cells per hour) than in other germ cells. These results indicate that in mature rats, not only Leydig cells and Sertoli cells but also germ cells have the capacity to express functional P450arom. According to the germ cell maturation state, there was an inverse relationship between P450arom mRNA content and the biological activity of the protein. The expression of the functional P450arom in mature rat germ cells confirms the existence of an additional source of estrogens within the genital tract of the male.

Increased Testicular Steroid Concentrations in Patients With Idiopathic Infertility and Normal FSH Levels

“…If we take into account the testicular localization of the estrogen receptors (alpha and beta) that are present in both somatic cells and germ cells [37], the negative role of estradiol is conceivable. Since the testicular level of testosterone is high, it is postulated that this androgen could be further aromatized not only in Leydig cells [21] but also in Sertoli cells [17] as well as in germ cells, especially in sperm as shown in rodents [14,18,27] and in humans [24]. In mice, estrogen regulates the reabsorption of fluid in the caput epididymis [19] via the modulation of the expression of aquaporin-1 [16], a pathway abolished in estrogen receptor alpha knockout mice [12].…”

“…The patients included in the infertile group (n = 10, mean age 29.8 ± 3.3 years; range [26][27][28][29][30] were selected during the advisory service (infertility status ranged between 3 and 6 years). All of them had normal caryotype and androgenic development; the blood FSH levels were in the normal range but they were infertile.…”

Teasing out the role of aromatase in the healthy and diseased testis

“…10), however we know from earlier work that transcript levels are not a direct indicator of enzymatic activity. 11 To understand the contribution of aromatase to testicular development and disease, we need to pinpoint its cellular localization within the testis, its expression at these sites, the cellular effects that occur in its absence and over abundance and elucidate the molecular mechanisms that underpin each of these events. This review synthesizes the data available, highlights important gaps in our understanding and attempts to develop new concepts for the role of aromatase in testicular function.…”

Expression of Sox9 in granulosa cells lacking the estrogen receptors, ERα and ERβ

“…Indeed, because both cell types have a common embryologic origin from the genital ridge (reviewed in Swain and LovellBadge, 1999) and are similar with respect to their functions of nurse cells for the germ cells and to their main regulation by the gonadotropin FSH, they express similar sets of genes, e.g., genes encoding AMH (Mü nsterberg and Lovell-Badge, 1991;Hirobe et al, 1992, and references therein), inhibin/activin (Griswold, 1993;Richards, 1994), c-kit ligand (Manova et al, 1993;Richards, 1994;Vincent et al, 1998), aromatase (Richards, 1994;Levallet et al, 1998), and SGP-2 (Ahuja et al, 1994;Aronow et al, 1993). Sox9 is one of the very few genes whose expression profile allows to unambiguously distinguish Sertoli and their precursors from granulosa cells: Sox9 is an early and permanent marker of the Sertoli cell lineage, as it starts to be expressed in the male genital ridge and is subsequently strongly expressed in fetal, postnatal, and adult Sertoli cells (Morais da Silva et al, 1996).…”