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  • Title: The protein kinase C content is increased in the nuclear fraction of rat adrenal zona glomerulosa following long-term ACTH administration.
    Author: Lehoux JG, Grondin F, Pacuraru JP, Yachaoui Y.
    Journal: Mol Cell Endocrinol; 1991 Jun; 78(1-2):97-106. PubMed ID: 1657659.
    Abstract:
    It is well known that the adrenal zona glomerulosa is transformed to zona fasciculata-reticularis in rats exposed chronically to ACTH. This model was used to study the intracellular distribution of protein kinase C, which is known to be involved in differentiation processes. Under basal conditions, in zona glomerulosa, 70, 23, and 7% of the protein kinase C was located in the cytosol, membrane and nuclear fractions, respectively. At 30 min after ACTH administration to rats, the protein kinase C content remained unchanged in the nuclear fraction, whereas that of the cytosolic fraction was decreased to 43% while in the membranes it was increased to 48%. After 2 days of ACTH treatment, we observed a significant increase, up to 25%, of protein kinase C in the nuclear fraction, a decrease to 47% in the cytosol, whereas the membrane fraction content had returned to its basal value. The intracellular distribution of inner zones was 17% in nuclear fraction, 47% in cytosol and 36% in membranes. ACTH treatments did not change these proportions. The total protein kinase C content of ACTH-treated groups was not different than that of their respective controls, in zona glomerulosa and in inner zones respectively. The cytosolic protein kinase C formed complexes with detergent-treated nuclei; this association was saturable, and could be measured by the ability of the kinase to bind [3H]PDBu ([20(n)-3H]phorbol-12,13-dibutyrate). The number of nuclear 'acceptor sites' thus measured was calculated to be 5245 fmol/mg DNA in the zona glomerulosa; this did not change significantly following a 3-day administration of ACTH. Protein kinase C prepared from the adrenal inner zones also bound zona glomerulosa detergent-treated nuclei but occupied fewer sites than the protein kinase C from the zona glomerulosa. In conclusion, the effects of chronic ACTH treatment on rat adrenal zona glomerulosa could be mediated by an increased level of protein kinase C in the nuclear fraction and possibly through its binding to specific 'acceptor sites'.
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