Exposure effects of levonorgestrel on oogenesis in the fathead minnow (Pimephales promelas)

Abstract

The synthetic progestin levonorgestrel is commonly utilized in human oral contraceptives. It enters the environment as a component of wastewater treatment plant effluent, and has been measured at low ng/L concentrations in surface waters. It has been shown to activate fish androgen receptors, causing the physical masculinization of females, changes in reproductive behavior, and decreases in fecundity. In the present study, the effects of levonorgestrel exposure on early-stage oogenesis in the fathead minnow (Pimephales promelas) was examined. Adult females were exposed to 0, 10, or 100 ng/L levonorgestrel for 14 d using a flow-through exposure system. The ovaries from each female were then removed via dissection and weighed for gonadosomatic index (GSI) calculations, and oocytes from one lobe preserved in Serra's fixative. Total numbers of late-stage vitellogenic oocytes exhibiting a germinal vesicle were then quantified. In a second exposure, blood plasma samples were collected from adult females and analyzed for vitellogenin concentrations using enzyme-linked immunosorbent assay. Females exposed to both concentrations of levonorgestrel developed male secondary sexual characteristics in a dose-dependent manner, and ovaries contained significantly fewer late stage oocytes. Exposure to 100 ng/L of levonorgestrel resulted in decreased GSI and blood plasma vitellogenin concentrations. The results suggest that female exposure to levonorgestrel alone may have profound effects on reproduction in progestin-contaminated environments. Environ Toxicol Chem 2017;36:3299-3304. © 2017 SETAC.

Exposure to levonorgestrel increases nest acquisition success and decreases sperm motility in the male fathead minnow (Pimephales promelas)

“…Over time, several generations of progestins have been developed, and are loosely classified based on the parent compound from which they are derived [5]. Laboratory exposure studies have recorded several effects associated with progestin exposure on reproduction in multiple fish species, including the masculinization of female fathead minnows [8,9] and eastern mosquitofish [10,11], changes to blood plasma sex steroid concentrations in the fathead minnow [9] and the common roach [12], decreased fecundity in the fathead minnow and Japanese medaka [8,9,13], alterations in normal reproductive behavior in the fathead minnow [8] and eastern mosquitofish [11], and decreased latestage oogenesis in female fathead minnows [14]. However, certain progestins (e.g., levonorgestrel and gestodene) have been shown to strongly bind and activate androgen receptors in the fathead minnow [2] and the Murray-Darling rainbowfish [7] with little to no activation of nuclear progesterone receptors, suggesting that some of the effects that are observed after exposure are controlled via androgen receptor-mediated pathways.…”

“…However, certain progestins (e.g., levonorgestrel and gestodene) have been shown to strongly bind and activate androgen receptors in the fathead minnow [2] and the Murray-Darling rainbowfish [7] with little to no activation of nuclear progesterone receptors, suggesting that some of the effects that are observed after exposure are controlled via androgen receptor-mediated pathways. Although several studies have examined the impacts of progestin exposure on female ex vivo ovarian steroid production [16], vtg1 messenger ribonucleic acid (mRNA) expression [17,18], plasma estradiol (E2) concentrations [12,13], and oogenesis [14,18] in several fish species, few studies have focused on the alteration in male reproductive fitness due to changes in behavior and gamete quality. When triads composed of 1 male and 2 female fathead minnows were exposed to gestodene [8] and levonorgestrel [15], females began to exhibit masculinized behavior after just 24 h of exposure.…”

“…However, certain progestins (e.g., levonorgestrel and gestodene) have been shown to strongly bind and activate androgen receptors in the fathead minnow [2] and the Murray-Darling rainbowfish [7] with little to no activation of nuclear progesterone receptors, suggesting that some of the effects that are observed after exposure are controlled via androgen receptor-mediated pathways. Laboratory exposure studies have recorded several effects associated with progestin exposure on reproduction in multiple fish species, including the masculinization of female fathead minnows [8,9] and eastern mosquitofish [10,11], changes to blood plasma sex steroid concentrations in the fathead minnow [9] and the common roach [12], decreased fecundity in the fathead minnow and Japanese medaka [8,9,13], alterations in normal reproductive behavior in the fathead minnow [8] and eastern mosquitofish [11], and decreased latestage oogenesis in female fathead minnows [14]. When triads composed of 1 male and 2 female fathead minnows were exposed to gestodene [8] and levonorgestrel [15], females began to exhibit masculinized behavior after just 24 h of exposure.…”

“…When triads composed of 1 male and 2 female fathead minnows were exposed to gestodene [8] and levonorgestrel [15], females began to exhibit masculinized behavior after just 24 h of exposure. Although several studies have examined the impacts of progestin exposure on female ex vivo ovarian steroid production [16], vtg1 messenger ribonucleic acid (mRNA) expression [17,18], plasma estradiol (E2) concentrations [12,13], and oogenesis [14,18] in several fish species, few studies have focused on the alteration in male reproductive fitness due to changes in behavior and gamete quality.…”

Progesterone affects sex differentiation and alters transcriptional of genes along circadian rhythm signaling and hypothalamic‐pituitary‐gonadal axes in juvenile Yellow River Carp (Cyprinus carpio var.)

“…Until recently, a number of studies had reported that P4 and synthetic progestins at low concentrations could cause reproductive endocrine disruption in fish. 5,[16][17][18][19][20][21][22][23][24][25] For instance, exposure to norethindrone at the juvenile stage could affect gonad differentiation and the sex ratio, which might be attributed to alterations in the transcriptional expressions of genes along the hypothalamic-pituitary-gonadal (HPG) axes. 20 Furthermore, 17α-ethynylestradiol can disrupt sexual differentiation, gonadal development, and reproduction in aquatic species.…”