EFFECT OF BOVINE GROWTH HORMONE AND A PARTIALLY PURE PREPARATION OF SOMATOMEDIN ON VARIOUS GROWTH PARAMETERS IN HYPOPITUITARY DWARF MICE

The growth-promoting effects of a partially purified preparation of somatomedin (12·7 units/mg) were compared with those of various doses of bovine GH (5, 20 and 80 μg/day) when injected into hypopituitary dwarf mice. Growth parameters studied were body-weight and tail-length velocities (calculated as the slope of a regression line fitted to daily measurements against time), uptake of 35SO2−4into costal cartilage in vivoand organ weights (heart, liver and kidney). In the first experiment somatomedin (6·4 units/day), bovine GH and 0·9% NaCl were injected once daily in a volume of 0·1 ml for 10 days. Treatment with bovine GH promoted a significant dose-dependent increase in body-weight and tail-length velocities and 35SO2−4uptake into costal cartilage in vivo. Somatomedin also promoted a significant increase in body-weight velocity and 35SO2−4uptake, both responses were between that observed with the lowest dose of bovine GH and control values. Somatomedin did not promote increase in tail-length velocity. Organ weights did not differ significantly between any of the treatment groups when expressed as mg/g body weight. In the second experiment somatomedin (a daily total of 21·6 units/day) and 0·9% NaCl were injected three times per day in a volume of 0·033 ml, bovine GH was again injected once daily in a volume of 0·1 ml, and the treatment period was 12 days. As in the first experiment all doses of bovine GH and somatomedin promoted a significant increase in body-weight velocity. These results are consistent with the somatomedin hypothesis.