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Calcium stimulates ornithine decarboxylase activity in cultured mammalian epithelial cells
Author(s) -
Langdon Robert C.,
Fleckman Philip,
McGuire Joseph
Publication year - 1984
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041180109
Subject(s) - cycloheximide , ornithine decarboxylase , egta , putrescine , calcium , extracellular , stimulation , medicine , endocrinology , chemistry , biochemistry , biology , protein biosynthesis , enzyme
Ornithine decarboxylase (ODC) activity usually rises to a peak a few hours after a trophic stimulus. The stimulation of ODC has been shown to depend on extracellular calcium in several in vitro eukaryotic systems. We have investigated the effect of calcium concentration on ODC activity and have found that ODC is stimulated when CaCl 2 alone is added to calcium‐deprived cells. Epithelial cells from calf esophagus were cultured and grown until stratified. Replacement of medium with fresh serum‐free medium resulted in stimulation of ODC activity, which peaked at 4 hours and declined to basal level by 10 hours. Subsequent depletion of Ca 2+ either by addition of ethylene glycol bis (β‐aminoethyl ether) N, N′‐tetraacetic acid (EGTA) or by replacement of medium with Ca 2+ ‐free medium, resulted in obliteration of ODC activity 4 hours later. Conversely, cultures in which medium was replaced with Ca 2+ ‐free medium and at 10 hours were repleted with Ca 2+ (either by addition of CaCl 2 or by replacement of medium with Ca 2+ ‐containing medium) exhibited a pronounced elevation of ODC activity 4 hours later. ODC activity peaked at 6 hours after the addition of CaCl 2 and declined by 8 hours. The effect was elicited by a wide range of concentrations of added Ca 2+ from 0.1 mM to 4.0 mM, but was maximal at 1.0 mM. ODC activity was totally abolished if either cycloheximide (10 μg/ml) or putrescine (10 mM) was added to cultures immediately prior to Ca 2+ addition. Actinomycin D (2, 5, or 10 μg/ml) added 30 minutes before Ca 2+ did not prevent the stimulation of ODC by added Ca 2+ . Stimulation by Ca 2+ is dependent on (1) absence of Ca 2+ during the initial 10‐hour incubation and (2) duration of incubation in Ca 2+ ‐free medium prior to Ca 2+ replenishment. The results indicate that Ca 2+ can increase ODC in epithelial cells exposed to Ca 2+ ‐depleted medium and that the increase in ODC depends on protein synthesis but is not inhibited by actinomycin D.