Studies on the esophagus. II. Enhancement of [ 3H]thymidine incorporation in the rat esophagus by Bidens pilosa (a plant eaten in south africa) and by croton oil

Bidens pilosa was collected in the Transkei, South Africa, or grown in a hothouse, and 1 : 4 mixtures of the dried leaves with a semisynthetic diet were administered to rats for 1–2 weeks. [ 3H] Thymidine incorporation into esophageal epithelial DNA was increased up to 2.3-fold. A somewhat smaller enhancement occurred with an ethanol extract of the leaves and with a fraction thereof, but not with raw spinach. Enhancement also occurred when B. pilosa was boiled under conditions resembling those used in its cooking. A small but significant increase of [ 3H] thymidine incorporation (up to 1.2-fold) occurred when 0.2–0.6% croton oil was administered in the diet for 1–2 weeks. Since tumor promoters usually cause cell proliferation, the results suggest that B. pilosa consumption might be a promoting factor in the etiology of esophageal cancer in the Transkei.