Nucleoside requirements for the in vitro growth of bovine aortic endothelial cells

The nutritional needs of cultured fetal bovine aortic endothelial cells were studied with regard to their nucleotide metabolism. When Medium 199 containing calf serum was supplemented with up to 5μg/ml of the deoxyribo‐ or ribonucleosides found in DNA or RNA, the rate of endothelial cell growth increased. The effect was entirely attributable to the pyrimidine nucleosides. The combination of deoxythymidine and deoxycytidine was much more effective than either deoxyribonucleoside used alone or than the combination of uridine and cytidine. Addition of deoxythymidine and deoxycytidine (each at 1 μg/ml) to the medium supported the growth of endothelial cell cultures from initially sparse populations (ca. 50 cells/cm 2 ), even at low concentrations (1%) of fetal bovine serum. The pyrimidine deoxyribonucleosides on their own were unable to stimulate cell growth; other bonafide growth stimulatory factors, such as those present in serum, serum dialysates, or retinal extracts, were needed in the medium to signal the initiation of DNA synthesis and cell replication. The significance of these findings with respect to improving cell performance under in vitro conditions and controlling endothelial cell growth in vivo are discussed.