SERUM LEVELS OF GH, IGF-I, LH AND OVARIAN-STEROIDS IN CYCLIC AND RU486-TREATED RATS

Rats lacking progesterone action due to RU486 treatment have been repo rted to show numerous endocrine and morphological similarities with re spect to human polycystic ovary syndrome (PCO), Nevertheless, abnormal ities on insulin or insulin-like growth factor I (IGF-I) production, a frequent finding in the polycystic disease, have not been studied in such rats yet, The aim of these experiments was to evaluate the serum concentrations of IGF-I in rats treated with 4 mg of the antiprogestag en RU486 over 4 or 8 consecutive days starting on estrus (day 1) and d ecapitated on the morning of day 5 and 9, Serum levels of growth hormo ne (GH), luteinizing hormone (LH), testosterone (T) and 17 beta estrad iol (E-2) were determined and correlated with those of IGF-I, Controls were rats injected with oil and killed in the morning of metestrus, d iestrus, proestrus and estrus, Rats treated with RU486 had increased s erum concentrations of IGF-I, LH, T and E-2 with respect to control ra ts on estrus, while no differences were found in the serum concentrati ons of GH, Parallel estrous cycle related changes were observed in the serum concentrations of IGF-I, T and E-2 with the highest values at p roestrus, However, changes on serum concentrations of GH were not asso ciated with those of IGF-I in control rats through the estrous cycle, The present results are consistent with the idea that beside on GH, se rum concentrations of IGF-I in the rat depend also on LH or LH-depende nt ovarian steroid production, Moreover, the results indicate that IGF -I production increased in RU486-treated rats, which may have a role i n the ovarian abnornalities induced by RU486 treatment in the rat. (C) 1997, Editrice Kurtis.