Type II and type III monodeiodinase activities in the skin of untreated and propylthiouracil-treated cashmere goats

The presence or absence of types I, II and III iodothyronine monodeiodinase enzymes (MDI, MDII and MDIII) and their levels of activity in the skin of goats, which were orally dosed for 60 days with 0, 1.1, 2.2, 4.4, 8.8, 17.5 , or 35 mg(-1)kg liveweight day(-1) of the anti-thyroid, enzyme-inhibiting drug, propylthiouracil (PTU), were determined. Contrary to our earlier repo rt that PTU did not influence skin MDII activity, the currect more thorough investigation tin terms of numbers of observations and the efficiency of t he enzyme extraction procedure) indicated that doses of 1.1. to 17.5 mg kg( -1) liveweight induced a 2 to 3 fold increase (P = 0.01) in MDII activity. However, in three of the four goats treated with 35 mg kg(-1) group, activi ty was similar to that of control animals. There were no significant differ ences between treatments in MDIII activity but there was a trend towards lo wer levels of activity in the goats dosed with 17.5 and 35 mg kg(-1). It is concluded that there is significant MDII and MDIII activity in the skin of goats and that although there is none of the PTU-sensitive MDI enzyme, syn thesis of T3 within the skin could nevertheless be modified through increas es in MDII activity induced by lower T4 concentrations in the circulation c aused by PTU. Changes in pattern of fibre moult induced by treatment with l ow doses of MD-inhibiting drugs may therefore be achieved through this effe ct. Since MDII and MDIII enzyme activity may be reduced by high doses of PT U, prolonged treatment with high doses of PTU may have adverse effects on s kin tissue. (C) 2000 Harcourt Publishers Ltd.