Effects of internally administered N-[5-(4-aminophenoxy)pentyl]phthalimide on wool follicles and skin of sheep.

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When N-[5-(4-aminophenoxy)pentyl]phthalimide was administered to sheep in sufficient quantities to permit manual removal of the fleece (400 mg/kg body weight orally, or 75 mg/kg body weight intravenously during a period of 48 h), cell division ceased in the wool follicle bulbs within 1 day. Dark-staining bodies (autophagic vacuoles) developed concomitantly in the cytoplasm of the bulb cells. The nuclei of cells in the keratogenous zones of the fibres became pycnotic 2 days after dosing and subsequent keratinization of these portions of the fibres was impaired. All the follicles retrogressed prior to day 7 after dosing, and the root ends which formed on the fibres moved towards the skin surface, reaching the level of the sebaceous glands by day 7. At this time mitotic activity recommenced around the dermal papillae in about 50% of the follicles. A small number of tips of new fibres emerged from the skin surface of some of the depilated sheep by day 14. The root ends on the fibres in the fleeces harvested at days 7-15 were fragmented with various degrees of taper. By 21 days, most follicles were growing emergent fibres. Thickening of the epidermis, increase in sebaceous gland size and decrease in skin thickness occurred in some of the depilated sheep. Smaller doses of the compound (200 mg/kg body weight orally or 40 mg/kg body weight intravenously during 24 h) produced weakness in the wool. Fewer autophagic vacuoles were present in follicle bulbs 1 day after dosing and not all follicles regressed. The weakened region of the fleece contained a mixture of shed fibre ends and continuously growing fibres with thin regions proximal to poorly keratinized lengths of fibre. No change was observed in other components of the skin of the sheep with weakened wool. The follicular changes produced by this compound are similar in some respects to those produced by other depilatory compounds or that occur during natural cyclic hair growth.