NA+-DEPENDENT, CONCENTRATIVE NUCLEOSIDE TRANSPORT IN RAT MACROPHAGES - SPECIFICITY FOR NATURAL NUCLEOSIDES AND NUCLEOSIDE ANALOGS, INCLUDING DIDEOXYNUCLEOSIDES, AND COMPARISON OF NUCLEOSIDE TRANSPORT IN RAT, MOUSE AND HUMAN MACROPHAGES

The effects of natural nucleosides and various analogs thereof on Na+-dependent, concentrative transport of formycin B by cultured rat macrophages were investigated. Concentrative transport is the sole nucleoside transport system of these cells. The results indicated that uridine, 5'-fluorouridine, all natural purine nucleosides, 2-chloroadenosine and 5'-deoxyandenosine are efficient substrates for the transporter. None of nine other pyrimidine nucleosides was transported. 3'-Deoxyadenosine, 2',3'-dideoxyadenosine, 8-azidoadenosine, tubercidin, 5'-methylthioadenosine 6-mercaptopurine riboside and adenosine arabinoside were either poor substrates or not transported significantly. The substrate activity of some of the natural nucleosides and the lack of substrate activity of 3'-deoxyadenosine, 2',3'-dideoxyadenosine, 8-azidoadenosine and 2',3'-dideoxycytidine were confirmed by direct uptake measurements. No significant concentrative nucleoside transport was detected in cultured human monocytes/macrophages, whereas mouse macrophages possessed both concentrative and equilibrative nucleoside transporters.