On the effect of vinblastine on ameloblasts of rat incisors in vivo. 2. Protracted effect on secretory ameloblasts. A...

The effects of vinblastine sulphate at a dosage of 0.2 mg per 100 g body weight on the secretory ameloblasts of rat incisors were studied 3, 6 and 24 hours and 3 and 7 days after administration of the drug. The vinblastine affected the secretion profoundly, caused a reduction in size of the cells and death of many ameloblasts. Most of the surviving ameloblasts restored initially-induced loss of polarity. Many also resumed secretion and deposition of enamel matrix. The Tomes' processess were extremely sensitive to vinblastine and all matrix deposited after administration of the drug appeared abnormal in structure. Ameloblasts not resuming secretory activity were less than half the size (height) of normal cells. In some areas all the ameloblasts were destroyed with the exception of a varying number of surviving ameloblasts parts consisting only of a nucleus and a small amount of cytoplasm. The ameloblasts which had re-established secretory activity, and most of the ameloblasts which had not, retained their ability to transform into transporting ameloblasts. Large amounts of ameloblast debris present 3 and 6 hours after administration of the vinblastine were effectively engulfed and digested by the cells of the striatum intermedium within 24 hours.