SERUM AND RENAL IGF-I LEVELS AFTER UNINEPHRECTOMY IN THE RAT

The hypertrophy of the remaining kidney following uninephrectomy (UNx) has been related to an increase in renal insulin growth factor-I (IGF -I) content. However, while the increase in renal IGF-I lasts for only days after UNx, renal hypertrophy continues for months. In the presen t study we investigated whether IGF-I also plays a role in the late po st uninephrectomy growth of the remaining kidney. Renal IGF-I in the r emnant kidney was greater than that of control kidneys (78.3 +/- 17.3 vs 56.0 +/- 14.0 pmol g(-1); p < 0.05)3 days after UNx, tended to rema in higher 30 days after UNx (83.8 +/- 23.6 vs 57.3 +/- 14.5 pmol g(-1) ; p = 0.07), but was similar to that of the control kidney when examin ed 60 days after UNx (66.6 +/- 15.6 vs. 70.4 +/- 6.7 pmol g(-1)). Seru m IGF-I in uninephrectomized rats was similar to that of controls 3 da ys after UNx, started to increase above the control level at day 10 af ter UNx and remained higher 30 and 60 days after UNx (75.9 +/- 6.9 vs. 48.7 +/- 7.3 nmol l(-1) at 30 days, and 81.2 +/- 13.7 vs 52.9 +/- 11. 0 nnol l(-1) at day 60, p<0.05 for both). The kidney weight of unineph rectomized rats was higher by 21% than that of controls 3 days after U Nx, by 45% 30 days after UNx and by 63% 60 days after UNx (p<0.05 for all three observations). At the end of the study, the glomerular volum e of uninephrectomized rats was higher by 36% than that of the control s (p<0.05). We suggest that in the rat, while the initial post unineph rectomy hypertrophy of the remnant kidney is associated with and most probably mediated by an increase in renal IGF-I, the hypertrophy;hat p ersists in later post UNx periods is associated with and may be mediat ed by an increase in serum IGF-I.