The growth-promoting effect of human whole blood serum on cultured human aortic smooth muscle cells is a constant serum donor-dependent property.

We studied the variation in the mitogenicity of sera derived from any particular subject at different time points. Two sets of sera were taken at an interval of 3 wk from 12 healthy male conscripts, and the samples were tested with regard to their ability to support proliferation of cultured human aortic smooth muscle cells (HSMC). Sera from 12 individuals showed markedly different growth-stimulating effects. On the other hand, sera from any particular individual taken at different time points gave constantly the same result. This was evident when the sera from the two time points were tested fresh in separate experiments and when they were tested together in one experiment after storage of 4 to 5 mo. The growth-promoting effects of the sera did not correlate significantly with the concentration of certain measurable serum factors which are known to be mitogenic for arterial smooth muscle cells (low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, growth hormone, insulin, or insulinlike growth factor-I). Our results indicate that the growth-promoting effect of human serum on cultured HSMC is a constant serum donor-dependent property. This implies that it is possible to make reliable comparisons between the growth-promoting effects of the sera derived from different subjects, and to measure the effects of treatments, e. g. medical or dietary, on the mitogenicity of the sera from any given individual.