ABSTRACT:We demonstrated previously that receiving long-term phototherapy was associated with early impairment of growth plate structure in neonatal rats, and oxidative stress may be the main risk factor for growth plate injury. The purpose of this study was to examine the histomorphometric effects of pentoxifylline treatment on the growth plate. Sixty weanling Sprague-Dawley rats were randomly separated into three equal groups. Group A, the control group, did not receive phototherapy and pentoxifylline. Groups B and C were exposed to phototherapy for 7 d. In addition to phototherapy, group C was also given pentoxifylline during the study period. Compared with zonal lengths on d 7 after initiation of phototherapy, group B had significantly lower values than group A for all zonal lengths (p Ͻ 0.001). Zonal lengths of growth plate were increased significantly with pentoxifylline treatment in group C for 7 d compared with group B (p Ͻ 0.001). After phototherapy, group B had significantly higher values than groups A and C for plasma malondialdehyde levels (p Ͻ 0.001). The pentoxifylline was found here to have some potential to reduce the effects of phototherapy on growth plate in neonatal rats at a relatively low dose. T he growth plate is a highly organized cartilage structure located between the epiphyseal and metaphyseal bones at the distal ends of the long bones (1). Longitudinal bone growth is the result of chondrocyte proliferation and subsequent differentiation in the epiphyseal growth plates of the long bones. It is regulated by a multitude of genetic and hormonal factors, growth factors, environment, and nutrition (2-5). Regarding effects of radiation therapy on chondrocytes, Pateder et al. observed no change in transforming growth factor  (TGF-) gene expression (6), whereas Margulies et al. found that TGF- expression decreased and fibroblast growth factor 2 increased after irradiation (7). Moreover, there is evidence that growth plate chondrocytes, osteoclast precursors, and vascular endothelial cells are more sensitive to radiation than osteoblasts (8 -10). All these contribute to establishing the final height of an individual.Phototherapy administered to newborns with jaundice is considered to be a rather benign procedure with few side effects such as rash, loose stools, increased insensible water loss, and dehydration (11). Although phototherapy has been in use for a long time and its effects on the body have been studied extensively, so far, no studies have investigated the relationship between the growth plate and phototherapy. We previously showed the damaging effect of phototherapy by increased oxidative stress on growth plate in newborn rats. Moreover, we showed functional damage and a harmful effect on longitudinal growth of phototherapy on the SpragueDawley rat growth plate (12). Therefore, we hypothesized that pentoxifylline would ameliorate the adverse effects of phototherapy on the growth plate.
METHODS
Study groups.Sixty weaning Sprague-Dawley rats were randomized into three groups. As all...