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A B S T R A C T Phagocytosis of erythrocytes was studied in vitro in an incubation system consisting of rat peritoneal macrophages and antibody-coated 'Fe-labeled erythrocytes. The system was characterized in terms of the rate and magnitude of erythrophagocytosis, determined by the interiorization of the 'Fe label. On incubation of 150 X 106 macrophages with 75 X 10 antibodycoated erythrocytes, erythrophagocytosis began within a few minutes and was essentially completed after 2 h when 50% of the offered red cells had been ingested by the macrophages. Heme oxygenase (HO) activity, which is very low in native macrophages, increased 4-to 10-fold in response to the ingested erythrocytes; this enzyme stimulation occurred with a delay of 3 h in relation to erythrophagocytosis. Actinomycin D or puromycin prevented the increase of HO activity without affecting erythrophagocytosis, which suggests that the enzyme stimulation was due to substrate-mediated enzyme induction.Hydrocortisone (HC) (0.1 mg/ml medium) dissociated erythrophagocytosis from HO induction, leaving the former unimpaired but completely suppressing the latter. The suppressive effect of HC on the enzyme induction was completely prevented by 5 mg glucose and 0.02 U insulin/ml of the medium. In macrophages engaged in erythrophagocytosis, HC also lowered glucose removal from the medium and reduced formation ofThese results suggest that induction of HO in macrophages by the hemoglobin of ingested erythrocytes requires intact transport or metabolism of glucose. GlucoseThis work was presented in part at

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We employed the photoaffinity probe 8-azido-adenosine 5'-triphosphate (aATP) to identify the nuclear envelope (NE) nucleosidetriphosphatase activity (NTPase) implicated in control of RNA transport. The photoprobe was hydrolyzed at rates comparable to those for ATP, with a Michaelis constant of 0.225 mM. Photolabeling was dependent upon UV irradiation (300-nm max) and was not affected by quercetin. Unlabeled ATP or GTP competed with [32P]aATP in photolabeling experiments, and UTP was a less effective competitor, paralleling the substrate specificity of the NTPase. Incubation of NE with aATP led to a UV, time, and concentration dependent irreversible inactivation of NTPase. The inactivation could be blocked by ATP or GTP. Polyacrylamide gel electrophoresis and autoradiography of photolabeled NE showed selective, UV-dependent labeling of a 46-kDa protein with both [gamma-32P]aATP and [alpha-32P]aATP. This band was not labeled with [gamma-32P]ATP. Since the NE NTPase implicated in RNA transport is modulated by RNA, we examined the effects of RNA on the labeling process. Removal of RNA from the NE preparations (by RNase/DNase digestion) reduced NTPase by 30-40% and eliminated photolabeling of the 46-kDa band. Addition of yeast RNA to such preparations increased NTPase activity to control levels and selectively reinstated photolabeling of the 46-kDa band. These results suggest that the 46-kDa protein represents the major NTPase implicated in RNA transport.