Sensitivity of fetal rat testicular steroidogenesis to maternal prochloraz exposure and the underlying mechanism of inhibition.
The fungicide prochloraz (PCZ) induces malformations in androgen-dependent tissues in male rats when administered during sex differentiation. The sensitivity of fetal testicular steroidogenesis to PCZ was investigated to test the hypothesis that the reported morphological effects from maternal exposure were associated with reduced testosterone synthesis. Pregnant Sprague-Dawley rats were dosed by gavage with 0, 7.8, 15.6, 31.3, 62.5, and 125 mg PCZ/kg/day (n = 8) from gestational day (GD) 14 to 18. On GD 18, the effects of PCZ on fetal steroidogenesis were assessed by measuring hormone production from ex vivo fetal testes after a 3-h incubation. Lastly, PCZ levels in amniotic fluid and maternal serum were measured using liquid chromatography/mass spectroscopy and correlated to the inhibition of steroidogenesis. Fetal progesterone and 17alpha-hydroxyprogesterone production levels were increased significantly at every PCZ dose, whereas testosterone levels were significantly decreased only at the two high doses. These results suggest that PCZ inhibits the conversion of progesterone to testosterone through the inhibition of CYP17. To test this hypothesis, PCZ effects on CYP17 gene expression and in vitro CYP17 hydroxylase activity were evaluated. PCZ had no effect on testicular CYP17 mRNA levels as measured by quantitative real-time polymersase chain reaction. However, microsomal CYP17 hydroxylase activity was significantly inhibited by the fungicide (K(i) = 865nM). Amniotic fluid PCZ concentrations ranged from 78 to 1512 ppb (207-4014nM) and testosterone production was reduced when PCZ reached approximately 500 ppb, which compares favorably with the determined CYP17 hydroxylase K(i) (326 ppb). These results demonstrate that PCZ lowers testicular testosterone synthesis by inhibiting CYP17 activity which likely contributes to the induced malformations in androgen-dependent tissues of male offspring.
Blystone
Chad R
CR
Department of Environmental and Molecular Toxicology, NC State University, Raleigh, NC 27695, USA.
Lambright
Christy S
CS
Howdeshell
Kembra L
KL
Furr
Johnathan
J
Sternberg
Robin M
RM
Butterworth
Brian C
BC
Durhan
Elizabeth J
EJ
Makynen
Elizabeth A
EA
Ankley
Gerald T
GT
Wilson
Vickie S
VS
Leblanc
Gerald A
GA
Gray
L Earl
LE
D019326:17-alpha-Hydroxyprogesterone / Q000097:blood / Q000378:metabolism; D000653:Amniotic Fluid / Q000378:metabolism; D059002:Androgen Receptor Antagonists; D000735:Androstenedione / Q000097:blood / Q000378:metabolism; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000096:biosynthesis / Q000097:blood; D005260:Female; D005333:Fetus / Q000187:drug effects / Q000378:metabolism; D005659:Fungicides, Industrial / Q000493:pharmacokinetics / Q000633:toxicity*; D015870:Gene Expression / Q000187:drug effects; D007093:Imidazoles / Q000493:pharmacokinetics / Q000633:toxicity*; D008297:Male; D010750:Phosphoproteins / Q000096:biosynthesis; D011247:Pregnancy; D011374:Progesterone / Q000096:biosynthesis / Q000097:blood; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D013254:Steroid 17-alpha-Hydroxylase / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics; D013256:Steroids / Q000096:biosynthesis*; D013737:Testis / Q000187:drug effects* / Q000196:embryology / Q000378:metabolism*; D013739:Testosterone / Q000096:biosynthesis / Q000502:physiology; D000098682:Steroidogenic Acute Regulatory Protein
D059002:Androgen Receptor Antagonists; D005659:Fungicides, Industrial; D007093:Imidazoles; D010750:Phosphoproteins; D012333:RNA, Messenger; D013256:Steroids; D000098682:Steroidogenic Acute Regulatory Protein; D013739:Testosterone; D000735:Androstenedione; D011374:Progesterone; D004958:Estradiol; D019326:17-alpha-Hydroxyprogesterone; C045362:prochloraz; D013254:Steroid 17-alpha-Hydroxylase