Nucleic acid metabolism of the neuroglial cells of the rat neural lobe

Abstract

Neural lobes taken from rats stimulated by water deprivation or salt loading showed an enhanced incorporation of [ 3H]uridine into total RNA in vitro. The incorporation of label into neural lobe RNA was linear over the time periods of the in vitro incubation and proportional to the DNA concentration. Radioautography demonstrated that the label was localized primarily in the nuclear regions of the pituicytes. The in vitro incorporation of [ 3H]uridine into the RNA of cerebral cortex, hypothalamus or peripheral nerve of control and stimulated rats was indistinguishable from each other. Furthermore, no significant differences could be found in the protein, RNA or DNA content of stimulated and control neural lobes despite the large increase in the incorporation of label into the RNA of stimulated neural lobes. Examination of the PCA-soluble radioactivity, as well as uridine phosphorylase and ribonuclease activities suggest that neither of the above factors play a decisive role in the observed increase in RNA labeling after stimulation by water deprivation. The temporal course of in vitro stimulation on the incorporation of [ 3H]uridine into neural lobe RNA has shown that both water deprivation and salt loading have a biphasic effect. The initial sharp increase in RNA labeling occurred between the second and third day of water deprivation and between the fifth and sixth day of salt loading. Both dehydration stimuli, however, resulted in an equivalent rate of loss of vasopressin content in the neural lobe ( i.e., 10%, 50%, and 90% after 1, 3 and 6 days respectively). The stimulated labeling response could be terminated after one day of rehydration, but then a rebound phenomenon was observed. The rat neural lobe represents a unique for studying possible functional relationships between neurosecretory neurons and neuroglial cells.