Abstract
Polychlorinated biphenyls (PCBs) are ubiquitous, persistent, organic pollutants also considered endocrine-disrupting chemicals. Our study examined the effects of lactational exposure to nondioxin-like PCB-155 and/or dioxin-like PCB-169 on longitudinal femur growth at the distal epiphyseal growth plate (EGP) in young rats at three different ages [postnatal days (PNDs) 9, 22, and 42]. After delivery, lactating rats were divided into four groups (PCB-169, PCB-155, PCB-155 + 169, and control) and administered PCBs intraperitoneally. The femurs of offspring were used to estimate growth rate (µm/day), and histomorphometric analysis on the distal femur included the thickness of the EGP and zones of proliferation and hypertrophy with calcification. Stereometry was used to determine trabecular bone volume density. In the PCB-169 and PCB-155 + 169 groups, PCB-169 affected longitudinal bone growth in the early postnatal period by interfering with chondrocytes in the EGP zone of proliferation and, to a lesser extent, the zone of hypertrophy. Morphometric alterations in EGP structure diminished until puberty. A slow growth rate persisted in the PCB-169 group until PND 42, while in the PCB-155 group, a fast growth rate between PNDs 9 to 22 was significantly reduced between PNDs 22 to 42. Sterometric assessment showed decreased trabecular bone volume in the PCB-155 + 169 group compared with that in the control on PND 9 and increased in the PCB-169 group compared with that in the PCB-155 group on PND 42. To summarize, studied PCB congeners exerted congener- and age-dependent effects on femur growth rate and its histomorphometric characteristics.
Highlights
Polychlorinated biphenyls (PCBs) are ubiquitous, persistent, organic pollutants considered endocrine-disrupting chemicals
We previously showed that offspring body mass, which is a general indicator of growth, was decreased compared with that of control rats in the PCB-169 and PCB-155 + 169 groups from postnatal days (PNDs) 9 o nward[20] and was accompanied by an alteration in prepubertal and pubertal rat femur length and biomechanics on PNDs 22 and 4220,21
In the second period (PNDs 22–42), the growth rate remained low in the PCB-169 group (p = 0.003), while in the PCB155 + 169 group, it reached a level comparable with the control group
Summary
Polychlorinated biphenyls (PCBs) are ubiquitous, persistent, organic pollutants considered endocrine-disrupting chemicals. Our study examined the effects of lactational exposure to nondioxinlike PCB-155 and/or dioxin-like PCB-169 on longitudinal femur growth at the distal epiphyseal growth plate (EGP) in young rats at three different ages [postnatal days (PNDs) 9, 22, and 42]. In Europe, their production and usage were banned more than 40 years ago, which enabled a stabilization of or, in some areas, a reduction in their levels in the environment and human diet, including mother’s milk[2] Still, their presence in the environment leads to their bioaccumulation in predator wild animals, as demonstrated in a marine mammal study in which the biopsied skin and blubber tissue from 87.5% of stranded free-ranging dolphins were shown to contain PCB concentrations above the toxicity threshold for physiological effects[3]. Our previous studies on dioxin-like PCB-169 and non-dioxin-like PCB-155 reported reduced body weight gain and impaired craniofacial growth in lactationally exposed young rats on PNDs 9 and 2219, alterations in femur bone geometry on PND 2 220, and biomechanics and mineral composition on PND 4221. Alterations in the femur on PNDs 22 and 42 were primarily induced by PCB-169, while the changes observed in the combined exposure group (PCB155 + PCB-169) were similar but less pronounced, which suggests that a nonplanar PCB-155 congener might reduce the PCB-169-mediated toxic effects in the b one[20,21]
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