The influence of D-penicillamine on the proliferation rate of cells from the upper limb bud of mouse embryos in vitro.

D-Penicillamine was given on the fourth day of culture of limb buds from 11-day mouse embryos at a dose of 100 microng/ml medium and allowed to react for 24 hours. On day 5 there was found a significant decrease in the [3H] thymidine labeling index of cartilage cells and of cells of the perichondrium, whereas mesenchyme cells showed no decrease in proliferation under these conditions. The toxic effects of D-penicillamine on prenatal skeletal developement in vivo could therefore result not only from direct action on collagen but also via inhibition of proliferation of cartilage cells.