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  • Title: Parallel activation of cyclic AMP phosphodiesterase and cyclic AMP-dependent protein kinase in two human gut adenocarcinoma cells (HT 29 and HRT 18) in culture, by vasoactive intestinal peptide (VIP) and other effectors activating the cyclic AMP system.
    Author: Mangeat P, Marvaldi J, Ahmed OA, Marchis-Mouren G.
    Journal: Regul Pept; 1981 Mar; 1(6):397-414. PubMed ID: 6262879.
    Abstract:
    Vasoactive intestinal peptide (VIP), secretin, catecholamines and prostaglandin E1 (PGE1) in the presence of a cyclic nucleotide phosphodiesterase inhibitor stimulate the accumulation of cyclic AMP in two colorectal carcinoma cell lines (HT 29 and HRT 18) with subsequent activation of the cyclic AMP-dependent protein kinases. In HT 29 cells incubated without phosphodiesterase inhibitor, 10(-9) M VIP promotes a rapid and specific activation of the lower Km cyclic AMP phosphodiesterase (1.7-fold); at 25 degrees C the effect is maintained for more than 15 min, while at 37 degrees C the activity returns to basal value within 15 min. As shown by dose-response studies, VIP is by far the most effective inducer (Ka equals 4 x 10(-10) M) of the cyclic AMP phosphodiesterase activity; partial activation of the enzyme is obtained by 3 x 10(-7) M secretin, 10(-5) M isoproterenol and 10(-5) M PGE1; PGE2 and epinephrine are without effect. In HRT 18 cells VIP is less active (Ka equals 2 x 10(-9) M) whereas 10(-6) M PGE1, 10(-6) M PGE2 and 10(-5) M epinephrine are potent inducers of th phosphodiesterase activity. The positive cell response to dibutyryl-cyclic AMP further indicates that cyclic AMP is a mediator in the phosphodiesterase activation process. The incubation kinetics and dose response effects of the various agonists on the cyclic AMP-dependent protein kinase activity determined for both cell types in the same conditions show a striking similarity to those of phosphodiesterase. Thus coordinate regulation of both enzymes by cyclic AMP was observed in all incubation conditions.
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