ATRIAL SEPTAL-DEFECT IN CYANOTIC CL FR MICE

Objective: It is widely known that some newborn CL/Fr mice with cleft lip and palate (CLP) also have cyanotic symptoms, which have been thou ght to depend on an atrial septal defect (ASD). In a previous study, w e found that cyanotic mice tended to have more severe types of CLP. We hypothesize that the mechanical airway obstruction due to a poorly de veloped palatal shelf and unmoved tongue in CLP(+) mice might be relat ed to the occurrence of cyanosis. The purpose of this study was to exa mine the relationships between ASD and cyanosis in CLP(+) newborns. Me thod: The newborn hearts from CLP(-), noncyanotic CLP(+), cyanotic CLP (+), CL/Fr mice and ICR mice were examined histologically, and the inc idence and size of ASD was determined on neonatal day (ND) 0. In CLP(- ) newborns, similar procedures were performed from ND 1 to ND 4. Furth ermore, in CLP(+) newborns, development of the palatal shelf was exami ned. Results: While all the ICR mice had a well-developed atrial septu m, and the incidence of ASD was 0%, about 80% of CL/Fr mice had ASD, i rrespective of the presence or absence of CLP and cyanosis. On ND 0, t he septum primum was significantly shorter in cyanotic CLP(+) mice tha n in CLP(-) mice. It also tended to be shorter in CLP(+) mice than in CLP(-) mice. Between the cyanotics and noncyanotics, there were no sig nificant differences in the incidences of ASD and the rate of septal d evelopment. In CLP(-) mice, the septum primum developed well later and no ASD was observed on ND 4. Cyanotic newborns had significantly less developed palatal shelves than did noncyanotics. Conclusions: Cyanosi s may not be related to ASD and the rate of septal development, but ma y be related to the occurrence of CLP in this strain. Furthermore, we confirmed that some relationship exists between the development of the palatal shelf and cyanosis. The present study supports our hypothesis concerning the cause of cyanosis in CL/Fr mice.