Male Sprague-Dawley Rats Exposed to In Utero Di(n-butyl) Phthalate

Abstract

When 100 mg/kg/day of di(n-butyl) phthalate (DBP) was intragastrically administered to pregnant Sprague-Dawley rats throughout gestation days 12 to 21, the male pups had similar body weights with no apparent physical differences (e.g., litter size, sex ratio) compared to that of the vehicle group. However, prominent age-related morphological alterations in the smooth endoplasmic reticulum (sER) of testicular Leydig cells (LCs) were observed once these animals reached puberty. At weeks 5 to 7, the abundant sER with non-dilated cisternae was distributed in LCs. Subsequently, although the number of LCs significantly increased, the amount of sER was significantly decreased at 9 to 14 weeks of age and had disappeared at 17 weeks. In contrast, the number of LCs and the amount of sER in LCs of the lower dose groups (10, 30, and 50 mg/kg/day) were similar to those of the vehicle group. Further, serum testosterone levels in the 100 mg/kg dose group were significantly lower during 5 to 17 weeks of age. While their luteinizing hormone (LH) level was significantly lower at 5 to 7 weeks of age, it became significantly higher during 9 to 17 weeks. The amount of sER in LCs decreased with age with the increase in LCs proliferation and serum LH levels in rat exposed in utero to DBP in a dose-dependent manner.

Effects ofin UteroExposure to Di(n-butyl) Phthalate for Estrogen Receptors α, β, and Androgen Receptor of Leydig Cell on Rats

“…Dose solutions were prepared fresh every morning and administered at 9:00 a.m. The regimen was based upon previous studies that illustrated the lowest-observed-adverse-effect level of DBP on fetal male rats at 100 mg/kg/day (Mylchreest, Cattley, and Foster 1998;Barlow and Foster 2003;Shirai et al 2013;Wakui et al 2013). Offspring were weighed and sexed at birth.…”

Nuclear Morphometric Analysis of Leydig Cells of Male Pubertal Rats Exposed <i>In Utero</i> to Di(<i>n</i>-butyl) Phthalate

“…Additionally, no decrease in litter size or pup survival, alteration of sex ratio or difference in body weights of male pups compared with controls on any day examined were found and the relative testicular weights of DBP groups were similar to those of the vehicle group (data not shown) 27 , 28 . However, by conducting routine toxicological pathological observation, the LCs observed in the 5- and 7-wk-old DBP groups did not display nuclear alterations or any other apparent toxicity (Fig.1).…”

“…The phthalate esters, including di( n -butyl) phthalate (DBP), have an estrogenic or anti-androgenic effect on the development of the male reproductive system, and the specific primary cellular target of DBP has been considered to be testicular Leydig cells (LCs) 22 , 23 , 24 , 25 , 26 . Recently we reported that prenatal administration of DBP induced atypical Leydig cell (LC) hyperplasia at nine weeks and older, although the numbers and proliferative activities of LCs were similar to those of the vehicle group until seven weeks 27 , 28 . The progression from normal structure to hyperplasia has been considered a continuous event 29 .…”

“…1. Representative features of Leydig cells nuclei of the 7-wk-old vehicle group (A) and 7-wk-old DBP group (B). DNA Feulgen stain without counterstain; bar = 25 μm.) 27 , 28 .…”

“…Dose solutions were prepared fresh every morning and administered at 9:00 am. The regimen was based upon previous reports that the lowest-observed-adverse-effect (LOAEL) dose of DBP in fetal male rats was 100 mg/kg/day 22 , 23 , 24 , 25 , 26 , 27 , 28 . Offspring were weighed and sexed at birth.…”