IT is now generally agreed that while haemolysis may play a part, the main factor in the production of the anaemia of chronic renal insufficiency is depression of erythropoicsis. This has been demonstrated by a number of recent in vivo studies in which impaired utilization of iiijccted radioiron has been found (Desforges and Dawson, 195 8 ; Loge, Langc and Moore, 1958;Joske, McAlister and Prankerd, 1956). The role of the erythropoietic hormone has attracted considerable attention in recent years, but although it now seems likely that hormone activity in thc serum of patients whose anaemia is due to chronic renal insufficiency is considerably less than that in other anaemic states, this does not appear to bc the whole explanation of the anaemia (Penington, 1961). lr. 1 vitro studies by Markson aiid Kciinie (1956) suggested that 'uraemic' serum inhibited the maturation of nornioblasts from active 'non-uraemic' marrows, and their findings were confirmed by Berman aiid Powsncr (1959).Further evidence of a similar nature was provided by Thorup, Strole and Leavcll (1958) and by Erslcv and Hughes (1960), who found delay in the removal of radioiron from the culture medium by marrow normoblasts suspended in uraemic serum.It seemed to us that the behaviour of marrow normoblasts in uraciiiic serum could be more closely studied by autoradiographic techniques. In the investigations reported here, we have used autoradiography to study the influence of uraemic serum on the uptake of radioiron by individual normoblasts in suspension cultures. We have also made a smaller nuinber of observations on the uptake of glycine-2-14C, which, like iron, is incorporated into the iiormoblasts in the course of haenioglobin synthesis, formate 14C, which is incorporated into thymine in the synthesis of DNA (Thomas and Lochte, 1957), and inethioniiie 3 5 S , which is utilized by both nucleus and cytoplasm, and which gives a measure of protein turnover (Lajtha, Ellis and Oliver, 1953).
MATERIALS AND METHODSMarrow fioniyioii-uraemic subjects ('normal marrow') was cultured in parallel in normal seruni aiid in the scruni ofpatients suffering from chronic renal insufficiency with its associated anaeniia ('uracniic serum'), using the method of Lajtha (1952). The appropriate isotopes were added, r clc. to each millilitre of culture mcdium, immediately before incnbation. High specific activity s9Fe (FcC13, I PC. per clg. Fe) was used, the substance being added to a 5 ycr ccnt solution of iraii-binding globulin to make a stock solution containing TO clc. 59Fe per nil. The cultures were incubated fcx 18 hours at 37" C., aiid the supernatant fluid was withdrawn and discarded. Smears were made and fixed by methyl alcohol. Autoradiographs were prepared by Lajtha's modification of the stripping film technique (Lajtha, 1954). After appropriatc exposure time (28-30 days for 59Fe, 6-8 days for glycine-z-14C, forniate 14C and riietliioiiine 35S), the slides were developed, fixed aiid stained by Giemsa's stain diluted I in 10. Th.e slides thus prcpared were sc...
