Effects of rhGH and rhIGF-1 on renal growth and morphology

It is known that in rodents recombinant human growth hormone (rhGH) and recombinant human insulin-like growth factor (rhIGF-1) increase renal mass. It is uncertain, however, whether renal mass increases in proportion to body growth, or whether renal growth is stimulated selectively. In 120 to 150 g female Sprague-Dawley rats, we measured the effects of rhGH and rhIGF-1 and their combination by the following parameters: kidney weight/body weight ratio, DNA/protein ratio, mRNA of GH receptor and of IGF-1, mitosis index and PCNA (by immunohistology), zonal architecture and glomerular diameter by micromorphometry. Both rhGH and rhIGF-1 dose-dependently increased renal weight and body weight over vehicle treated controls. With rhGH, liver dry weight/body weight ratio increased, but kidney dry weight/body weight ratio remained unchanged (0.99 +/- 0.06 x 10(-3) vs. 1.02 +/- 0.07 in vehicle controls). In contrast, a significant increase of kidney dry weight/body weight ratio was seen in rats treated with rhIGF-1 (1.3 +/- 0.21 x 10(-3). Addition of high doses of rhGH to high doses of rhIGF-1 caused no further increase of the ratio despite a significant further increase of body weight. rhGH increased the abundance of renal GH receptor mRNA (0.46 +/- 0.32 amol/microgram DNA vs. 0.08 +/- 0.07 in controls) and of IGF-1 mRNA (1.35 +/- 0.5 pg/micrograms DNA vs. 0.35 +/- 0.17), whereas no change was seen with IGF-1 treatment. rhGH and rhIGF-1 increased kidney DNA/protein ratio, mitoses and PCNA expression in various renal structures.(ABSTRACT TRUNCATED AT 250 WORDS)