Expression of GH receptor, IGF-I receptor and IGF-I mRNA in the kidney and liver of rats recovering from unilateral renal ischemia.

The role of the growth-hormone (GH), insulin-like growth factor-I (IGF-I) axis in the kidney has been extensively studied in recent years. To further elucidate the role for GH and IGF-I in renal regeneration, the expression of the GH-rec, IGF-I-rec and IGF-I mRNA was studied in the post-ischemic regenerating kidney and in the liver of the same rats, using a solution hybridization assay. Rats were subjected to 90 min of unilateral renal ischemia followed by reperfusion. The kidneys and livers were collected 1, 3 and 7 days after injury. Five animals were operated on in each group. An additional five animals were sham-operated and killed on day 4. In the kidney, significant alterations were found in the expression of mRNAs for the GH-rec and the IGF-rec. The GH-rec mRNA decreased significantly at day 1 (P < 0.01) to less than one-fifth of the initial value, and normalized at days 3 and 7. The IGF-rec mRNA levels increased more than three-fold at day 3 (P < 0.01) and more than five-fold at day 7 (P < 0.01). In the kidneys there was no significant alteration in the IGF-I mRNA level. In the liver, significant alteration in the level of the GH-rec mRNA was found, while the levels of IGF-rec and the IGF-I mRNA did not change significantly. The levels of GH-rec mRNA increased two-fold at day 3 (P < 0.05), while the levels were unchanged at days 1 and 7. In the early phase of renal regeneration, there is a sharp decrease in the expression of GH-rec mRNA in the kidney. This suggests that there are no direct effects on renal tissue mediated by GH in this situation. There is a significant increase in the intrarenal IGF-I-rec mRNA levels from day 3, suggesting an increased need for IGF-I during regeneration. In the liver, the concentration of GH-mRNA is increased significantly at day 3. These data show on alterations that suggest a role for these factors in renal regeneration.