Perfusion cultures of human bone marrow mononuclear cells (BMMNC) provide a unique in vitro model of hematopoiesis, supporting growth of both accessory and hematopoietic elements. In this study, bioreactors were used to analyze the consumption and production of growth factors (GFs) in relation to each other and to the cells produced. The exogenously added GFs interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), stem cell factor (SCF), and erythropoietin (Epo) each exhibited different, but reproducible, consumption kinetics. Epo and IL-3 were consumed slowly for the first 5-7 days, and then the consumption rate of both increased. Epo consumption reached a plateau by day 10, whereas IL-3 consumption continued to increase. Consumption of SCF was similar to that of Epo, but began 2-3 days earlier. GM-CSF was consumed throughout the culture period in an accelerating manner. Consumption of SCF and Epo were related, because omission of Epo from the growth medium reduced SCF consumption by 53% and omission of SCF reduced Epo consumption by 82%. A reproducible relationship between cumulative GF consumption and total cell production was observed. Epo was most potent, with 5900 molecules consumed per cell produced, whereas 69,400 molecules of SCF were consumed per cell generated. More specifically, Epo consumption was correlated (r = 0.92 and 0.96) with the number of glycophorin A-positive (glyA+) cells produced, and the rate of Epo consumption varied with the progression of cells through the erythroid lineage. Consequently, measurement of GF consumption rates may be useful for quantifying the types of cells present in a culture. Endogenous GF production was also examined. G-CSF and MIP-1 alpha were present at high levels during the first 4 days but then declined rapidly. LIF first appeared in the second week and steadily increased thereafter. Omission of SCF from the medium allowed the detection of endogenous SCF production, and the kinetics was similar to that of LIF. IL-6 production was biphasic, with a peak and decline in week 1 and an increase during week 2. TGF-beta was below the level of detection in these cultures. The results suggest that perfusion supports accessory and hematopoietic elements which interact and therefore represent a partially functional tissue ex vivo. This system provides a useful model for studying relationships within GF networks and for elucidating the conditions that result in primitive cell expansion ex vivo.