Novel molecular targets associated with testicular dysgenesis induced by gestational exposure to diethylhexyl phthalate in the rat: a role for estradiol.

Significant research has been focused on phthalate-induced alterations in male reproductive development. Studies on rodents have prompted the notion that a syndrome exists in the human male which includes phenotypic alterations such as hypospadias, cryptorchidism, poor semen quality, and even testicular cancer. Each phenotype in this 'testicular dysgenesis syndrome' is predicated on reduction in testosterone production by the fetal Leydig cell. We sought to examine the relationship between dysgenesis and steroidogenic capacity in the fetal rat testis more stringently by incorporating lower exposures than those typically used, conducting a comprehensive, non-targeted quantitative evaluation of the fetal testis proteome, and relating alterations in individual proteins to the capacity of the fetal Leydig cell to produce testosterone, and histopathology of the fetal testis. Pregnant dams were dosed orally from gestation day (GD) 13-19 with 0, 10, or 100 mg diethylhexyl phthalate (DEHP)/kg body weight per day. Each endpoint was represented by 16l. Clustering of Leydig cells occurred before any significant decrease in the capacity of the GD19 Leydig cell to produce testosterone. At 100 mg DEHP/kg, testosterone production was reduced significantly, Leydig cell clusters became quite large, and additional dysgenetic changes were observed in the fetal testis. Of 23 proteins whose expression was altered significantly at both DEHP exposure levels, seven were found to be correlated with and predictive of the quantified endpoints. None of these proteins have been previously implicated with DEHP exposure. Notably, pathway analysis revealed that these seven proteins fit a pathway network in which each is regulated directly or indirectly by estradiol.

Low iron diet and parenteral cadmium exposure in pregnant rats: the effects on trace elements and fetal viability.

The effects of latent iron deficiency combined with parenteral subchronic or acute cadmium exposure during pregnancy on maternal and fetal tissue distribution of cadmium, iron and zinc, and on fetal viability were evaluated. Timed-pregnant Sprague-Dawley rats were fed on semisynthetic test diets with either high iron (240 mg kg) or low iron (10 mg kg), and concomitantly exposed to 0, 3 or 5 mg cadmium (as anhydrous CdCl2) per kilogram body weight. Animals were exposed to cadmium from gestation day 1 through 19 by subcutaneously implanted mini pumps (Subchronic exposure) or on gestation day 15 by a single subcutaneous injection (Acute exposure). All rats were killed on gestation day 19. Blood samples, selected organs and fetuses were removed and prepared for element analyses by atomic absorption spectrometry. Low iron diet caused decreases in maternal body weight, maternal and fetal liver weights, placental weights and tissue iron concentrations. By cadmium exposure, both subchronic and acute, tissue cadmium concentrations were increased and the increase was dose-related, maternal liver and kidney zinc concentrations were increased, and fetal zinc concentration was decreased. Cadmium concentration in maternal liver was additionally increased by low iron diet. Acute cadmium exposure caused lower maternal body and organ weights, high fetal mortality, and decreased fetal weights of survivors. In conclusion, parenteral cadmium exposure during pregnancy causes perturbations in essential elements in maternal and fetal compartments. Acute cadmium exposure in the last trimester of gestation poses a risk for fetal viability especially when combined with low iron in maternal diet.

Assessment of steroid disruption using cultures of whole ovary and/or placenta in rat and in human placental tissue.

OBJECTIVES: The paper presents results of collaborative research on cadmium as an endocrine disruptor. To detect steroidogenic alterations in cycling and pregnant rats following cadmium exposures in vivo (at 3 or 5 mg/kg as a single s.c. dose) and in vitro (from 0 through 2000 microM Cd(2+)) whole-ovary culture was used. To evaluate steroid productions in rats fed low iron (10 ppm) and concomitantly exposed to cadmium (5 mg/kg total dose by s.c.-implanted osmotic pumps) during 19 days of pregnancy whole-placenta culture was also used. In human placental tissue cadmium and progesterone concentrations were assessed in relation to cigarette smoking. METHODS: Cultures of minced ovaries were evaluated for 1-h basal steroid production and following 1-h production stimulated with either human chorionic gonadotropin (hCG) or hCG and pregnenolone. Placental cultures were evaluated for average 1-h progesterone production following 3 h of unstimulated production. Steroid hormones were evaluated by specific radioimmunoassay. Placental cadmium concentrations were analyzed by atomic absorption spectrometry. RESULTS: In-vivo cadmium exposure interfered with normal steroidogenesis in cycling rats and in early pregnancy, with ovarian estradiol production the most affected. Under in-vitro cadmium exposure the most affected was ovarian production of progesterone and testosterone in cycling (proestrous) rats with medial inhibitory concentrations under 500 micro M Cd(2+). Cadmium interfered with the steroidogenic pathway at more than one site. Linear and additive effects of low-iron feeding and concomitant cadmium exposure during pregnancy on placental progesterone production were found. In humans, we found that the placentas of smoking mothers contained twice as much cadmium and approximately half the amount of progesterone than did the placentas of non-smoking mothers. CONCLUSIONS: Results of the research on cadmium-induced steroidogenic effects using cultures of whole rat ovary and/or placenta as well as human placental tissues point to cadmium as an endocrine disruptor that may compromise pregnancy outcome and fetal viability.