Persistence of carbadox-induced adrenal lesions in pigs following drug withdrawal and recovery of aldosterone plasma concentrations.

ABSTRACT

This study was performed to investigate the persistence of carbadox-induced adrenal lesions in pigs after withdrawal of the drug. Six groups (N = 13) received 0 (control group), 25, 50, 100 and 200 ppm carbadox. After 10 weeks, carbadox was withdrawn from the feed. Five and 11 weeks after withdrawal, two pigs per group were necropsied and the adrenals were examined histologically. Five weeks after withdrawal, recovery of lesions was seen in the 25 and 50 ppm groups. In the 100 and 150 ppm groups, adrenal changes were still present. After 11 weeks an incomplete recovery occurred in the 100 ppm group and in one of the pigs from the 150 ppm group; the second pig of this group still demonstrated moderate changes. Pigs from the 200 ppm group showed severe changes and absence of a clear zonal differentiation. Plasma aldosterone values started to recover 2 weeks after withdrawal of carbadox. Histological examination suggested stimulation of the aldosterone-producing glomerular zone, eventually resulting in regressive changes. The mechanisms that possibly induced this continuous stimulation are discussed.