Adenosine 3′,5′‐cyclic monophosphate‐mediated enhancement of calcium‐evoked prolactin release from electrically permeabilised 7315c tumour cells

1 The 7315c tumour cell was used as a model system for the investigation of adenosine 3′,5′‐cyclic monophosphate (cyclic AMP)‐mediated enhancement of calcium‐evoked prolactin release. 2 7315c cells were permeabilised by subjecting the cells to intense electric fields. Studies investigating the penet...

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Bibliographic Details
Published in:British journal of pharmacology 1988-07, Vol.94 (3), p.737-744
Main Authors: Guild, Simon, Frey, Elisabeth A., Pocotte, Susan L., Kebabian, John W.
Format: Article
Language:English
Subjects:
Animals
Biological and medical sciences
calcium
Calcium - physiology
Cell Membrane Permeability
Cyclic AMP - physiology
Egtazic Acid - pharmacology
Electric Stimulation
Ethidium
Fundamental and applied biological sciences. Psychology
Hormones and neuropeptides. Regulation
Hypothalamus. Hypophysis. Epiphysis. Urophysis
prolactin
Prolactin - metabolism
Radioimmunoassay
Rats
Tumor Cells, Cultured
Vertebrates: endocrinology
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Summary:1 The 7315c tumour cell was used as a model system for the investigation of adenosine 3′,5′‐cyclic monophosphate (cyclic AMP)‐mediated enhancement of calcium‐evoked prolactin release. 2 7315c cells were permeabilised by subjecting the cells to intense electric fields. Studies investigating the penetration of the dye ethidium bromide indicated that the cells were completely permeabilised after 2 discharges of 2000 volts and that the pores remained open for at least 30 min before beginning to reseal. These permeabilisation parameters were consistent with those which gave maximal calcium‐stimulated prolactin release. 3 In the absence of calcium and in the presence of EGTA (1 mm), permeabilised 7315c cells secreted prolactin at a rate of 0.23 ng min−1 per 106 cells. When EGTA was replaced by 1.5 mM calcium, permeabilised cells secreted prolactin at a rate of 2.20 ± 0.30 ng min−1 per 106 cells in the first 5 min of exposure. Maximal calcium‐dependent prolactin secretion from permeabilised cells occurred at 37°C. 4 The amount of prolactin secreted, in a 5 min incubation at 37°C, from permeabilised cells depended upon the free calcium concentration in the permeabilisation medium. Calcium stimulated prolactin release from permeabilised cells in the concentration range 0.1–10 μm (half maximal = 5.8 μm). When permeabilised cells were exposed to cyclic AMP (100 μm) for 5 min prior to and during a 5 min challenge with various concentrations of calcium, the amount of prolactin secreted at each effective concentration of calcium was increased. However, cyclic AMP did not alter the potency of calcium as a stimulant of prolactin secretion. 5 The results suggest that cyclic AMP potentiates calcium‐evoked secretion from 7315c cells, not by increasing the entry of calcium into the cytosol, but at a step in the secretory process, distal to calcium entry, which modulates the ability of an increase in cytosolic calcium concentration to stimulate prolactin release.
ISSN:0007-1188
1476-5381
DOI:10.1111/j.1476-5381.1988.tb11583.x