Growth medium containing serum from young diabetic subjects caused a significant stimulation both of cell proliferation and of the outgrowth in cultures of rabbit aortic medial cells above that noted with normal human sera. The addition to the sera of guinea-pig human growth hormone antibody caused a marked inhibition of these stimulatory effects. The growth effect of rabbit serum was not affected by the human growth hormone antiserum.
Reinvestigation of the effect of human growth hormone disclosed that the same increase as observed in growth with the diabetic sera could be obtained with a growth hormone concentration of 0.2 ng. per milHliter medium.
The present results strongly suggest that the increased stimulatory effect of normolipemic human diabetic serum on growth and cell proliferation of aortic medial cell cultures is due to increased serum growth hormone concentration.