Effect of varied membrane protein density on the lateral diffusion of lipids in the mitochondrial inner membrane

with the exception of platelets which were treated with O.O~M-EDTA and 0. I5M-NaCI in 0.05hf-Tris buffer, pH7.4. A small aliquot of each of the cell preparations was removed for enumeration. The cell suspensions, together with an aliquot of plasma, were then diluted with trichloroacetic acid to a final concentration of 5% (w/v). The samples were thoroughly mixed and left overnight at 4°C. After centrifugation the acidic supernatants were removed and their ascorbic acid contents were estimated colorimetrically using the dinitrophenylhydrazine procedure of Denson & Bowers (1961). The results for the ascorbic acid content of plasma, platelets, erythrocytes, lymphocytes, monocytes and polymorphonuclear leucocytes for the three subject groups are shown in Fig. I . There is significantly more plasma ascorbic acid in the young controls as compared with the old controls (P< 0.05) and similarly in the young controls as compared with the cancer patients (Ppolymorphonuclear leucocytes reveals varying amounts of ascorbic acid (as pg/108 cells) in the ratio of 6 : 12 : 1 (young controls), 4 : 7 : 1 (old controls) and 3 : 5 : 1 (cancer patients). It is possible that ascorbic acid is required by lymphocytes and monocytes for immune competence and further work may reveal whether this different intercellular distribution, between the three groups, parallels the decrease in cellmediated immunity observed in similar subject groups (Hannigan et al., 1983).