Influence of growth hormone deficiency on growth and body composition in rats: site-specific effects upon adipose tissue development.

Neonatal female rats were treated for 3 weeks (short term) or 8 weeks (long term) with antiserum to rat GH (anti-rGH) with or without replacement therapy with recombinant bovine GH (bGH). Body weight gain and tail length were significantly suppressed within the first 3 weeks and were even more markedly suppressed when treatment was continued for 8 weeks. When treatment was stopped in short-term-treated animals the rate of body weight gain recovered, although without evidence of catch-up growth. These effects were all normalized by concurrent treatment with bGH. Long-term anti-rGH treatment caused a profound reduction (80%) in the number of differentiated adipocytes in two internal fat depots, whilst the subcutaneous depot was only moderately affected (20%). In contrast, after recovery from short-term treatment with anti-rGH, the internal depots were only marginally decreased in both weight and adipocyte numbers, whereas the subcutaneous depot was actually doubled in size compared with controls, due entirely to an increase in the number of differentiated adipocytes. These data clearly demonstrate for the first time that GH is required for the differentiation of adipocytes in vivo. In addition, the results demonstrate distinct effects at different anatomical sites and suggest that GH may be one factor responsible for the differences described in numerous metabolic parameters and hormonal sensitivities of adipose tissue derived from different locations within the body.