Changes in wool follicles of sheep following administration of dexamethasone trimethylacetate

Intramuscular injection of 50 mg dexamethasone trimethylacetate produced variable effects on the fleeces of Merino sheep, ranging from an obvious discontinuity in the fleece, due to inhibition of growth of the majority of fibres, to no macroscopically observable effect. In the most affected animals, the mitotic activity and size of the follicle bulbs decreased during the first five days. Subsequently, fibre and inner root sheath cells withdrew from around the dermal papillae and were replaced by cells from the outer root sheaths. Autophagic vacuoles developed in these replacement cells. Regression of follicles proceeded until brush-ends formed on the fibres after 9–15 days. The amount of glycogen decreased inthe outer root sheath cells, which exhibited various responses at different levels in the follicles. The proportion of regressed follicles and to some extent the rate of regression were highest in the sheep with the most obvious discontinuity in the fleece. Regeneration of follicles was well advanced in all sheep 29 days after the injection.