Long-term effects of neonatal treatment with dexamethasone, L-carnitine, and combinations thereof in rats.

Because L-carnitine (L-CAR) is a potential substitute for neonatal dexamethasone (DEX) with respect to the prevention of long-term side effects, rats were treated on d 1, 2, and 3 after birth with saline, DEX, L-CAR, half the dose of DEX, and L-CAR + half DEX. DEX led to growth retardation, increased mortality, and severe kidney damage at 50 wk of age. L-CAR had no negative effects on growth, kidney function at 50 wk, and survival at 101 wk. Growth retardation was induced transiently by half DEX and permanently by L-CAR + half DEX, slightly reduced kidney function but no reduced life span was found in both these groups. Except for the DEX group, blood glucose levels were normal at 50 wk in all groups. A serendipitous finding was that L-CAR treatment caused one-third less food intake; however, these rats maintained normal body weight. In conclusion, L-CAR, a lower dose of DEX, and their combination caused less negative effects in later life. Because L-CAR + half DEX had a negative effect on growth, attention to monitor L-CAR levels during DEX treatment of preterm newborns seems to be justified. The finding that neonatal L-CAR caused reduced food intake in later life warrants further investigation.