Comparison of the effects of four hyperplastic agents on hamster cheek pouch mucosa.

Hyperplasia in the hamster cheek pouch was examined using 4 different hyperplastic agents: oil of turpentine 50% v/v in liquid paraffin; vitamin A palmitate 10% w/v in liquid paraffin; 12-O-tetradeconyl-phorbol-13-acetate 16nM in acetone; and ethylphenylpropiolate 0.04mM in acetone. Acetone, paraffin and untreated control groups were also examined. Cheek pouches were painted 3 times a week for up to 4 weeks with each solution. Samples were removed and prepared for light microscopy 24 hours after 2 weeks of painting and 24 hours, 6, 12 and 18 weeks after 4 weeks of painting. Hyperplasia was produced by application of turpentine, vitamin A and TPA after 2 weeks of application. Further increases in epithelial width occurred after 4 weeks of painting in the turpentine and vitamin A groups but a decrease was seen in the TPA group. Six weeks (vitamin A and TPA groups) or 12 weeks (turpentine group) after the completion of treatment the epithelium had a normal histological appearance. No differences between the control or EPP treated cheek pouch mucosa could be detected. Turpentine and vitamin A can be used as models of reversible hyperplasia in the hamster cheek pouch.