Skeletal developmental effects of selective and nonselective cyclooxygenase-2 inhibitors administered through organogenesis and fetogenesis in Wistar CRL:(WI)WUBR rats

Cyclooxygenase (COX) inhibitors are the most commonly ingested drugs. The aim of the study was to evaluate the prenatal skeletal effect of selective (DFU) and nonselective (tolmetin, ibuprofen, piroxicam) COX-2 inhibitors. All the tested compounds were administered intragastrically to pregnant Wistar rats from 7 to 21 gestation day. The initial dose was set at 8.5 mg/kg/dose for tolmetin and ibuprofen, 0.3 and 0.2 mg/kg/dose for piroxicam and DFU. The middle dose was increased 10-times. The highest dose, except for ibuprofen, was elevated 100-times. The highest dose for ibuprofen was set at 200 mg/kg/dose. Tolmetin and ibuprofen were administered three times a day. Piroxicam and DFU were dosed once daily. After routine teratological examinations, extremities of randomly selected 21-day-old fetuses were taken for histological, immunohistochemical and molecular studies. The proximal femoral epiphyses were separated and their ultrastructure evaluated. The expression of genes coding cytokines (IL-1α, IL-1β, IL-6, TNF-α, TNF-β) and proteins (COX-1, COX-2, cathepsin K, collagen types I, II and X; osteocalcin, osteopontin) was evaluated in femoral epiphyses by RNase Protection Assay and/or immunohistochemically. The articulate development was checked histologically and found undisturbed in any of the experimental groups. The epiphysis of the 21-day-old fetuses, presented physiological expression of COX-1 and COX-2, as well as cathepsin K, collagen types I, II and X; osteopontin, osteocalcin and TNF-α. Increased developmental skeletal variation was noted in groups exposed to the highest dose of nonselective drugs. Unlike the increased number of skeletal variations observed in fetuses exposed to highest doses of nonselective compounds, both groups of COX inhibitors did not disturb joint formation and morphology of femoral epiphyses when administered even in high maternal toxic doses.