Mechanism underlying the olfactory disturbance induced by an intraperitoneal injection of tributyltin chloride in rats

Acute intoxication by tributyltin compounds has been known to induce olfactory disturbances, although the underlying mechanism remains unclear. This study investigates the acute effect of tributyltin chloride (TBTC) on the olfactory bulb in rats. The time-course characteristics of the intra-olfactory concentration of TBTC, the histopathological changes of the olfactory bulb and the olfactory function were examined for 96 h after a single intraperitoneal injection of 2.5 mg/kg of TBTC. The olfactory function was evaluated by the discriminating ability for a cycloheximide solution which has an unpleasant odor for rats. The concentration of TBTC in the olfactory bulb, which was measured using gas chromatography/mass spectrometry, quickly increased to a peak value within 24 h and then decreased. The viable cell number significantly decreased after the TBTC administration in the mitral cell layer and granule cell layer of the olfactory bulb, while apoptotic cells significantly increased in these areas at the same time. Hyposmia was evident 96 h after the TBTC injection, although olfactory testing could not been performed until that time because of anorexia. These results suggest that intraperitoneally injected TBTC was promptly transferred to the olfactory bulb through the blood–brain barrier, induced apoptosis of the cells in the olfactory bulb and finally elicited the olfactory disturbance.