Defect of nephrogenesis induced by gentamicin in rat metanephric organ culture.

BACKGROUND

In the rat, in utero exposure to gentamicin during early renal differentiation leads to a permanent nephron deficit. The aim of the present study was to analyze, in vitro, the potential direct effect of gentamicin on early nephrogenesis.

EXPERIMENTAL DESIGN

We used paired rat metanephric organ cultures from 14 (F14) or 15-day-old (F15) fetuses. We measured gentamicin accumulation into explanted metanephroi and then assessed in vitro growth in the absence or presence of the drug. Glomerular labeling and counting were performed on the whole explant to analyze the effect of antibiotics on early nephrogenesis.

RESULTS

Growth of F14 metanephric explants in the presence of 50 micrograms of gentamicin/ml was significantly reduced from 4 days onwards as compared to controls, whereas F15 explants grown with gentamicin displayed a normal in vitro development. After 6 days of culture, F14 and F15 explants had the same accumulation of gentamicin (1 microgram/mg protein) but the gentamicin content was 4 times larger in F15 explants. At both ages, gentamicin-exposed metanephric explants exhibited a significant reduction in their number of nephrons. However, the effects of 50 micrograms of gentamicin/ml on nephrogenesis were significantly more drastic on F14 than F15 explants (35% versus 18%). When grown with 0.5 microgram of gentamicin/ml, F14 explants still exhibited a 16% defect in nephrogenesis as compared with controls, and about the same reduction was observed for cultures in the presence of 100 micrograms/ml of streptomycin and 100 IU/ml of penicillin. Incubation of F14 explants with streptomycin alone for 6 days had no effect on nephrogenesis.

CONCLUSIONS

These results indicate that gentamicin induces a significant reduction in the number of nephrons in metanephric explants and that this effect is more important on less differentiated metanephroi. Metanephric organ culture combined with glomerular labeling represents a useful model to test the effect of various growth factors and other drugs on early nephrogenesis.