Metabolic response of nuclear and cytoplasmic pyridine nucleotides.

Abstract

1. The conditions are described in which the microfluorimetric-microelectrophoretic technique can be used for a comparative study of fluorescence changes due to reduced pyridine nucleotides in the cytoplasm and nucleus of irradiated and non-irradiated Chang and EL2 cells, treated with a variety of glycolytic substrates. So far there is considerable simultaneity in the nuclear and cytoplasmic responses, thus no evidence that the nuclear membrane functions as a diffusion barrier to the penetration of these substrates. 2. Nuclear and cytoplasmic responses to FDP show parallelism in aerobic-Dicumarol- or Rotenone-treated EL2 giants produced by X-irradiation. However if FDP is supplemented with GIP, 6-PG and UDPG or if G6P containing microelectrophoretic mixtures are used, metabolic discrepancies appear between the cytoplasm and nucleus of EL2 giants. In aerobic cells cytoplasmic responses are generally lower than nuclear responses, but the former are considerably enhanced by Rotenone, while the nucleus is practically Rotenone-insensitive. Similar observations are made with Chang giants. 3. The non-irradiated cells differ from their irradiated counterparts in two ways: at aerobiosis their nuclear and cytoplasmic responses are weaker (EL2SG) or nil (Chang cell); in presence of Rotenone both nuclear and cytoplasmic responses are enhanced. 4. The metabolic discrepancy between the cytoplasm and nucleus of the giants could be explained by radiation damage to the oxidative system of the nucleus, the lack of such a system in the nucleus or simple cytological considerations related to the considerable nuclear enlargement and its bearing on the diffusion gradient of oxygen.