Assessment of adult skeletons to detect prenatal exposure to trypan blue in mice

Publisher Website
Google Scholar
Abstract
A Skeletal Variant Assay System (SVAS) consisting of a group of 88 spontaneously occurring qualitative variations of the adult mouse skeleton was studied in CD‐1 mice which had been exposed in utero by way of three daily ip injections of their dams on days 7–9 of gestation with trypan blue. Treatment groups received daily doses of 0.25 cc of 0, .037, .075, .15, or .30% trypan blue dissolved in 0.9% NaCl. Two separate series of experiments were performed, and skeletons were examined at 62 ± 2 days postnatal. Sixty‐six and 58 of the variants occurred in the two series, respectively. Frequencies of occurrence of substantial numbers of variants differed from Untreated (UNTD) and Vehicle‐Treated (VEH) values in a dose‐related manner for both series. At the high dose 18 and 22 variants occurred with significantly different (P < .01) frequencies from UNTD in the two series. Contrasting high‐dose animals with vehicle controls revealed significant differences in 24 and 17 variants. There were 13 and 14 variants in the two series, respectively, which differed from both UNTD and VEH. If one considers differences at P < .01 in one comparison and P < .05 in the other, then 22 and 18 variants qualify as being signficantly different from both controls in the two series. Agreement between the two series was excellent regarding which variants were affected. Several differed significantly from both UNTD and VEH in both series of experiments. Among these were a number which appeared more or less specific to trypan blue exposure. They include Dyssymphysis of the Atlas, Carpal Fusions, and Tarsal Fusions. Although increased frequency of an Interfrontal bone is seen with several treatments, the magnitude of the response and the low doses at which it is elicited are unique to trypan blue exposure. Numerous low‐dose effects are striking in this set of experiments, making the SVAS a very sensitive indicator of trypan blue exposure. In addition to the variants mentioned, a large cluster of cervical (C) vertebrae variants, including dyssymphyses, fusions, imperfect transverse foramina of C1 and C2, and accessory transverse foramina of C3–C6, as well as vertebral fusions at various levels (especially cervical, sacral, and caudal), appear to be the principal effects of exposure to this compound. In addition, rib malformations at the high dose level, and increased frequency of occurrence of 27‐presacral vertebrae at all dose levels, were important effects. By all criteria applied, the SVAS is able to detect prenatal exposure to trypan blue in adult skeletons even in the absence of any gross morphological abnormalities, and can detect exposure at well below the teratogenic dose level.