Comparative evaluation of amiodarone-induced phospholipidosis and drug accumulation in Fischer-344 and Sprague-Dawley rats.

Amiodarone (AD) and its major metabolite, desethylamiodarone (desethylAD), are both phospholipogenic. The present study was undertaken to evaluate the comparative susceptibilities of male Fischer-344 and Sprague-Dawley rats to AD-induced phospholipidosis in alveolar macrophages (AMs), liver and kidney tissue and the concomitant accumulation of AD and desethylAD in these cells, tissues and plasma. Rats were administered AD (100 mg/kg/day, p.o.) for 1 week. Plasma concentrations of AD and desethylAD were approximately 4- and 12-fold higher, respectively, in Fischer-344s compared to Sprague-Dawleys 24 h after the last dose. AD and desethylAD levels in AMs were approximately 12- and 25-fold higher, respectively, in Fischer-344s than Sprague-Dawleys. In the liver and kidney, levels of both compounds were also significantly higher in Fischer-344s than Sprague-Dawleys. Ultrastructural features indicative of phospholipidosis were not observed consistently in any tissue except AMs from treated Fischer-344s. AM total phospholipid increased nearly 5-fold in Fischer-344s, while Sprague-Dawleys showed no increase over control. AMs from both strains incubated with 10 microM AD or desethylAD in vitro were not significantly different in their accumulation of the compounds. When incubated with AD or desethylAD, the lysosomal phospholipases A1 partially purified from AMs of both strains were equally sensitive to inhibition as measured by the drug concentration giving 50% inhibition in activity (IC50). The results of this study indicate that at the same administered dose, AD and desethylAD, accumulate to higher tissue levels and are more phospholipogenic in male Fischer-344 rats than in male Sprague-Dawley rats. The basis for the high susceptibility of Fischer-344 rats to AM-induced phospholipidosis is unknown at present but appears not to be related to biochemical or cellular features of the AMs.

In vivo and in vitro reversibility of chlorphentermine-induced phospholipidosis in rat alveolar macrophages.

Chlorphentermine (CP) is a cationic, amphiphilic drug (CAD) that has been studied widely for its ability to induce phospholipidosis, a disorder characterized by excessive accumulation of cellular phospholipid and ultrastructural development of lysosomal lamellar bodies (LLBs) in the cell. The accumulation of inducing drug correlates with increasing phospholipids. In the present study, we examined the reversibility of this disorder in rat alveolar macrophages (AMs) following a 7-day treatment (30 mg/kg/day, ip). The reversibility of phospholipidosis was examined under in vivo conditions and under in vitro conditions in cell cultures for a period of up to 12 days. There was a marked reduction in cellular CP levels and phospholipid content after 4 days of recovery, both in vivo and in vitro; however, there was no indication of significant loss of LLBs. Beyond this time point, ultrastructural recovery from phospholipidosis lagged behind the biochemical recovery temporally and was somewhat less rapid in vitro than in vivo. By 12 days of recovery, AMs from both groups had recovered biochemically, but a moderate level of LLBs was still present in some AMs in the in vitro recovery group. The results of this study indicate that there are more similarities than differences when comparing the recovery of phospholipidotic cells in vitro to that occurring in vivo. We conclude that the use of cell cultures may prove valuable in studying the reversibility of CAD-induced phospholipidosis.