Effects of Maternal Exposure to Low Doses of DES on Testicular Steroidogenesis and Spermatogenesis in Male Rat Offspring

Abstract

Abstract.Our previous studies have demonstrated that prenatally administered diethylstilbestrol (DES) impairs testicular endocrine function in male offspring. The present study examined whether maternal DES treatment influences testicular steroidogenesis and spermatogenesis. DES was injected subcutaneously at 0.5 or 1.5 μg/kg/day (DES 0.5 and 1.5 groups, respectively) into pregnant SD rats on days 7-21 of gestation. Male offspring in the DES 0.5 and 1.5 groups were autopsied at 1, 3, 6 and 15 weeks after birth. At 1 week, DES treatment did not lead to a change in the volume of P450scc-positive cells (Leydig cells), suggesting that DES has no inhibitory effect on the development of Leydig cells. DES administration disrupted luteinizing hormone receptor (LHr) expression and exerted inhibitory effects on signal transduction from LHr to steroidogenic acute regulatory protein (StAR) in testicular steroidogenesis (P<0.05), although there were no changes in the mRNA expression levels of steroidogenic enzymes, such as P450scc, 3β-hydroxysteroid dehydrogenase (3β-HSD) and P45017α, which may have caused a decrease in the plasma testosterone level. DES treatment did not disrupt the cycle of spermatogenesis but did upregulate the expression levels of androgen receptor (AR) mRNA in both DES groups at 15 weeks (P<0.05). These results indicate that maternal DES treatment disrupts steroidogenesis but induces a high level of AR mRNA expression to counteract the low levels of testosterone during spermatogenesis. uring embryonic development, rat primordial germ cells appear in the yolk sac on embryonic day 10, and the gonadal primordium begins to develop as the genital ridge around embryonic day 11. Primordial germ cells begin to reach the genital ridge on embryonic day 12 [1]; thereafter, Sertoli and Leydig cells in the male differentiate from genital ridge cells, leading to a series of differentiation events. The duration of pregnancy is generally divided into periods of embryonic development (first trimester), organogenesis (second trimester) and organ maturation (third trimester).Diethylstilbestrol (DES), a synthetic non-steroidal estrogen, exhibits strong estrogenic activity by binding to estrogen receptors (ERs). It has been shown that the treatment of pregnant rats with DES dose-dependently (range: 10 to 300 μg/kg) suppresses testosterone levels in the blood and testes of male fetuses [2-4]. We administered doses of DES much lower (1.5 μg/kg) than those previously applied to pregnant rats at 7-21 days of gestation (in the second and third trimesters) and demonstrated that DES suppresses plasma testosterone levels in adolescent male offspring (6 weeks after birth) [5].Androgen plays an important role in the development and function of the testis and male reproductive tract via the androgen receptor (AR). Similarly, since ERs have been found in these tissues [6][7][8][9][10], estrogen may be involved in development of the male reproductive system. Nevertheless, it is apparent that male ER-or aromatase-knockout mice initially ...

Accumulated HSV1-TK Proteins Interfere with Spermatogenesis through a Disruption of the Integrity of Sertoli-Germ Cell Junctions

“…Since the produced transgenic rats showed male infertility, heterozygote offspring were obtained by crossing a transgenic female rat with a normal male rat. The animals were individually housed in standard plastic rodent cages in a temperature-controlled environment with standard rat diet and water available ad libitum in a 12-h light/ dark cycle [9]. The experimental procedures were approved by the Institutional Animal Care and Use Committee of Meiji University.…”

Maternal Exposure to Low Doses of DES Altered mRNA Expression of Hepatic Microsomal Enzymes in Male Rat Offspring

“…5). In our previous study [15], DES, administered during the fetal stage, reduced plasma LH level for three weeks after birth, the plasma testosterone levels of the DES1.5 (6 weeks old) and DES0.5 (15 weeks old) groups decreased, but the release of gonadotropins from the pituitary gland did not increase in response to this change. To compensate for the decreased testicular testosterone level due to DES, the AR (androgen receptor) mRNA expression level in the testicles increased, and the spermatogenesis in the testicles was rescued from the inhibitory effects of DES.…”

“…To compensate for the decreased testicular testosterone level due to DES, the AR (androgen receptor) mRNA expression level in the testicles increased, and the spermatogenesis in the testicles was rescued from the inhibitory effects of DES. However, the altered mRNA expression levels of enzymes associated with testicular steroidogenesis were found to be not directly correlated with the decreased plasma testosterone levels [15]. Therefore, we considered that the steroid metabolism in the liver, responsible for the maintenance and excretion of circulating hormones, might be altered by DES and contribute to the decreased plasma testosterone level.…”

“…Since then, many reports have appeared on the undesirable effects of DES on the reproductive systems of men and women [12] as well as experimental animals [1,19]. Numerous studies have used prenatal or postnatal exposure to DES, mostly in high-dose ranges from 10 to 300 mg/kg, to induce gross adverse changes in the developing male reproductive system, e.g., testicular cancer, reduced testicular size and sperm production [10,19,20,24].We administered doses of DES much lower (1.5 g/kg) than those previously applied [10,11,29] to pregnant rats at days 7-21 of gestation (in the second and third trimesters), and demonstrated that DES induced not only suppression of plasma testosterone levels in adolescent male offspring (6 weeks after birth), but also promoted follicular maturation in female offspring [36,37]; in addition, maternal DES treatment disrupted steroidogenesis but increased the expression level of androgen receptor (AR) mRNA to inhibit the disruption of spermatogenesis to thereby counteract the low level of testosterone in testis [15].Secreted hormones exert their effects and are subsequently degraded in the liver to be excreted. Steroid hormones are maintained through a dynamic balance between steroidogenesis and inactivation to ensure their physiological functions.…”

“…We administered doses of DES much lower (1.5 g/kg) than those previously applied [10,11,29] to pregnant rats at days 7-21 of gestation (in the second and third trimesters), and demonstrated that DES induced not only suppression of plasma testosterone levels in adolescent male offspring (6 weeks after birth), but also promoted follicular maturation in female offspring [36,37]; in addition, maternal DES treatment disrupted steroidogenesis but increased the expression level of androgen receptor (AR) mRNA to inhibit the disruption of spermatogenesis to thereby counteract the low level of testosterone in testis [15].…”