US EPA

1181206 

Journal Article 

Effects of boric acid on axial skeletal development in rats 

Narotsky, MG; Schmid, JE; Andrews, JE; Kavlock, RJ 

1998 

Yes 

Biological Trace Element Research
ISSN: 0163-4984
EISSN: 1559-0720 

66 

1-3 

373-394 

English 

10050931 

10.1007/BF02783149 

WOS:000078563300029 

http://dx.doi.org/10.1007/BF02783149
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is related to other volume(s) 4983017 Effects of single-day boric acid treatment on axial skeletal development in rats

Prenatal exposure to elevated levels of boric acid (BA) causes reduced incidences of supernumerary ribs and shortening/absence of the 13th rib in multiple laboratory species. To explore this further, Sprague-Dawley rats received 500 mg/kg b.i.d. on gestation days (gd) 5-9, 6-9, 6-10, or on single days between gd 6 and 11 (plug day = gd 0); gd-21 fetuses were stained for skeletal examination. Following multiday exposures, malformations of the axial skeleton involved the head, sternum, ribs, and vertebrae. Shortening/absence of the 13th rib was seen particularly in the gd 5-9 and 6-10 exposure groups. Although most groups exposed on single days were generally unaffected, about 90% of the gd-9 exposed fetuses had only six cervical vertebrae; the deficient region was usually C3-C5. In contrast, gd-10 treatment caused agenesis of a thoracic/lumbar vertebra in over 60% of the fetuses; the deficient region was usually T11. For 13-ribbed fetuses, the length of rib 13 was shortened compared to controls. Postnatal assessment suggested increased mortality for gd-10 exposed pups. Embryos in culture showed reduced development when exposed to BA for 48 h. These findings demonstrate the critical periods for axial development in the rat and provide an experimental model for the study of homeotic shifts. 

boric acid; boron; axial skeleton; somite; rib; vertebra