In vitro and in vivo ultrastructural changes induced by macrolide antibiotic LY281389.
High doses of LY281389 (9-N-(n-propyl)-erythromycylamine) cause cytoplasmic vacuolar changes in striated and smooth muscle characteristic of drug-induced phospholipidosis. This study characterized phospholipidosis in striated and smooth muscle of rats and dogs, compared in vivo observations with those in a cultured rat myoblast model, and attempted to confirm the lysosomal origin of the drug-induced vacuoles. Standard transmission electron microscopy and acid phosphatase cytochemistry techniques were used to evaluate ultrastructural changes in vivo and in vitro. Rats and dogs exposed to LY281389 had a time- and dose-related increase in number and size of vacuoles containing concentric lamellar figures in cardiac and skeletal muscle. Cytochemical staining of dog stomach smooth muscle for acid phosphatase, a lysosomal enzyme, stained the periphery of vacuoles that contained concentric lamellar figures. Cultured rat L6 myoblast cells were exposed to 0.25 mg LY281389/ml for 2.5, 5, 10, 20, 30, or 90 min and 2, 6, 12, 24, or 48 hr. Cell cultures exposed for 2 hr had several predominantly large, clear, membrane-bound vacuoles, and at 6 and 12 hr there were greater numbers of large vacuoles that contained increased amounts of membranous figures. Following 24- or 48-hr exposures, vacuoles occupied most of the cytoplasmic volume, and were engorged predominantly with amorphous or granular material. These findings indicate that LY281389 can induce similar phospholipidosis-like vacuolar changes in rat and dog muscle and in a cultured rat muscle cell line. Further, positive acid phosphatase staining of drug-induced vacuolar structures, in conjunction with standard transmission electron microscopy techniques, strongly suggests that vacuoles seen in vitro and in vivo are lysosomal in origin.
Horn
J W
JW
Toxieology Research Laboratory, Lilly Research Laboratories, A Division of Eli Lilly and Company, Greenfield, Indiana 46140-2517, USA.
Jensen
C B
CB
White
S L
SL
Laska
D A
DA
Novilla
M N
MN
Giera
D D
DD
Hoover
D M
DM
D000135:Acid Phosphatase / Q000378:metabolism; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002460:Cell Line; D004285:Dogs; D004917:Erythromycin / Q000031:analogs & derivatives* / Q000494:pharmacology; D006651:Histocytochemistry; D008854:Microscopy, Electron; D009130:Muscle, Smooth / Q000187:drug effects* / Q000648:ultrastructure; D051381:Rats; D011916:Rats, Inbred F344; D014617:Vacuoles / Q000187:drug effects
D000900:Anti-Bacterial Agents; C066283:9-N-(1-propyl)erythromyclamine; D004917:Erythromycin; D000135:Acid Phosphatase