A comparison of the glucocorticoid receptor system in the spinal cord and hippocampus

Studied under in vivo conditions, uptake of [3H]corticosterone (CORT) by purified cell nuclei of the hippocampus was much higher than in the spinal cord, although the latter may contain in cytosol up to 50% of glucocorticoid receptors found in cytosol of hippocampus. Experiments were undertaken to explain these differences. First, the in vivo affinity of receptors for exogenous CORT was comparable in both tissues. Second, an inhibitor of translocation, although present, was not preferentially concentrated in the spinal cord as compared to the hippocampus. However, the sensitivity towards RNAase A, an enzyme that increased binding to DNA-cellulose (taken as a measure of increased affinity for nuclear components), was preserved in the hippocampus but absent in the cord. We discuss the possibility that refractoriness to RNAase A may play a role in the reduced nuclear uptake of [3H]CORT shown by the spinal cord in vivo, but also consider possible that heterogeneity of receptor types binding CORT in the spinal cord and hippocampus may account for the differences observed in both tissues.