Repairability of drug-induced "wavy ribs" in rat offspring.

The development and repairability of "wavy ribs" were studied in offspring from dams of rat strain SD-JCL dosed with fenoterol, a beta-adrenoceptor stimulant. The incidence of "wavy ribs" was high at 1000 mg/kg/d. The critical administration period for the development of "wavy ribs" was from day 13 through 17 of gestation. Firstly, a delay of ossification in the middle of the ribs was seen on day 17. Thereafter, the middle part of the ribs began to curve and the curves were calcified until the end of gestation. Decreases of alkaline phosphatase and total protein were observed on day 20 in blood of fetuses showing "wavy ribs". The "wavy ribs" gradually disappeared until weaning. The effect of fenoterol could be partially blocked by the action of a beta-adrenoceptor blocker.