Twelve ram lambs bred for resistance or susceptibility to sporidesmin dosing were operated on under general anaesthetic and T-way catheters inserted into the common bile duct to facilitate collection of bile. After a recovery period of 14 days the animals were given an oral dose of sporidesmin at a rate of 0.08 mg/kg/d over 3 consecutive days. A trace amount of 35S-labelled sporidesmin was also given on the first and third day of dosing to allow quantitation of sporidesmin appearing in the bile fluid. Bile samples were collected at 0.5 to 1 hourly intervals for 24 hours after the first and third dosing. Results showed bile concentrations of sporidesmin increasing to a maximum in 1 to 3 hours and then declining over the following 20 hours. There was considerable individual variation among animals in the pattern of uptake and in the maximal concentration reached after dosing. In some animals there was a marked increase in biliary sporidesmin from the first to the third oral dosing while other animals showed little observed increase at these times. A positive correlation (P<0.05) was found between liver- damage score at slaughter and maximum sporidesmin concentration in bile after the third but not the first oral dosing. These findings raise the possibility that an initial or 'potentiating' dose of sporidesmin may be required before 'susceptibility' or ' resistance' to facial eczema is expressed.

RW, Kelly, RP Lewer, AJ Allison, A Paterson, and M Howarth

Proceedings of the New Zealand Society of Animal Production, Volume 43, , 205-208, 1983
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