Effects of terbinafine on growth, squalene, and steryl ester content of a celery cell suspension culture

The allylamine terbinafine inhibited growth of a celery (Apium graveolens) cell suspension culture (I₅₀ = 90 μM) and blocked the action of squalene epoxidase, resulting in an accumulation of squalene and a decrease in the sterol content of the cells. Celery cells were tolerant to squalene accumulation; inhibition of growth of cultures was associated with a fall in the free sterol content below about 1 μg sterol/mg dry wt of cells. At Day 14, untreated celery cells contained about 60% of the total sterol in the esterified form. However, the steryl ester pool was considerably lower in terbinafine-treated cells which may reflect an attempt to maintain the free sterol content above a threshold value. The composition of free sterols of terbinafine-treated cells was different from control cultures, suggesting that terbinafine has a second site of inhibition on the pathway to major sterols in plants.