The Effects of Intrauterine Tetracycline Exposure on the Proliferating Chondrocytes of the Growth Plate of Mice Long Bones

Abstract

The proliferating chondrocyte of the growth plate (GP) contributes to the longitudinal growth of long bones. Tetracycline is a broad spectrum over-the-counter antibiotic, which reduces fetal bone growth. This study is meant to investigate the precise effect of intrauterine 12 mg/kg body weight (mbw) of tetracycline on the number, size and arrangement of proliferating chondrocytes on mice longitudinal bone growth. 12 mbw of tetracycline dissolved in normal saline was orally administered to 5 pregnant mice daily between the 11th and 15th day of gestation. Appropriate volume of normal saline was administered to 5 control pregnant mice. Fetuses were harvested on the 20th day of gestation by caesarian section. The humeri and femora were fixed in 10% formal saline, and histological slides were made using Toluidine blue as the stain. Dimensions and cellular population of the proliferating zones were noted using an ocular micrometer. Evidences of growth retardation were not noted in this study. The experimental humeral length was significantly shorter than the control. The proliferating zone cellular density in the distal GP of the experimental humerus was significantly higher than the control. There was a disruption of the columnar arrangement of the proliferating chondrocytes in the experimental humeral GP. Tetracycline (12mbw) does not have any significant effect on mice somatic growth. The disruption of the columnar arrangement of the proliferating chondrocytes in the humeri proximal GP contributed to the limb shortening effect. The sparing of the femur is in keeping with the differences in the timing of limb development.