Postnatal Evaluation of Cervical Ribs in Control Rats

Area of Science:

• Developmental toxicology
• Skeletal biology
• Teratology

Background:

• Cervical ribs are common in control rat fetuses and can be induced by maternal exposures.
• Postnatal evaluations of cervical ribs in rats are limited.
• Previous literature suggested no significant increase in postnatal cervical rib incidence in controls.

Purpose of the Study:

• To evaluate the incidence of cervical ribs in control rats during postnatal development.
• To compare perinatal and postnatal skeletal evaluations in a developmental toxicity study.

Main Methods:

• A developmental toxicity study using Sprague-Dawley rats exposed via inhalation to filtered air.
• Two cohorts: one for fetal skeletal evaluation on gestation day (GD) 21, and one for adult skeletal evaluation on postnatal day 65.
• Skeletal assessment for cervical ribs in both fetuses and adults.

Main Results:

• The incidence of cervical ribs increased significantly from 1.0% in fetuses (GD 21) to 12.7% in adults (postnatal day 65).
• This increase was observed in the control group, suggesting a developmental phenomenon rather than solely an exposure effect.

Conclusions:

• Postnatal development can lead to an increased incidence of skeletal abnormalities like cervical ribs in control rats.
• Further research is needed to understand the mechanisms of postnatal skeletal development.
• These findings are crucial for accurate human risk assessment in developmental toxicity studies.