Reconstitution of calcium-regulated parathyroid hormone secretion from streptolysin-O-permeabilized parathyroid cells by guanosine 5'-O-(thio)triphosphate

Intracellular Ca2+ levels determine the amount of PTH secretion from parathyroid cells. Dissociated calf parathyroid cells were permeabilized with streptolysin-O (SLO) to provide an in vitro model system to examine Ca(2+)-dependent regulation of hormone secretion. PTH release from these cells was en...

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Bibliographic Details
Published in:Endocrinology (Philadelphia) 1997-03, Vol.138 (3), p.1170-1179
Main Authors: Matovcik, L M, Rhee, S S, Schaefer, J F, Kinder, B K
Format: Article
Language:English
Subjects:
Animals
Bacterial Proteins
Calcium - pharmacology
Calcium-Calmodulin-Dependent Protein Kinase Type 2
Calcium-Calmodulin-Dependent Protein Kinases - physiology
Cattle
Cell Membrane Permeability - drug effects
Cyclic AMP - pharmacology
Cytosol - physiology
Energy Metabolism
Guanine Nucleotides - pharmacology
Guanosine 5'-O-(3-Thiotriphosphate) - analogs & derivatives
Guanosine 5'-O-(3-Thiotriphosphate) - pharmacology
Osmolar Concentration
Parathyroid Glands - drug effects
Parathyroid Glands - secretion
Parathyroid Hormone - antagonists & inhibitors
Parathyroid Hormone - secretion
Parotid Gland - physiology
Streptolysins - pharmacology
Time Factors
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Summary:Intracellular Ca2+ levels determine the amount of PTH secretion from parathyroid cells. Dissociated calf parathyroid cells were permeabilized with streptolysin-O (SLO) to provide an in vitro model system to examine Ca(2+)-dependent regulation of hormone secretion. PTH release from these cells was energy dependent and increased by cytosolic cofactors. Guanosine 5'-O-(thio)triphosphate (GTP gamma S) increased PTH secretion from SLO-permeabilized cells in a dose-dependent manner from 0.1-100 microM. In the absence of GTP gamma S there was no relationship between the ambient Ca2+ concentration and the rate of PTH secretion. However, in the presence of GTP gamma S, intracellular Ca2+ inhibited PTH secretion with an EC50 of approximately 0.1 microM, corresponding to physiological intracellular Ca2+ levels. Thus, the addition of GTP gamma S to SLO-permeabilized parathyroid cells reconstituted the inverse relationship between extracellular Ca2+ and PTH secretion that is observed in vivo and in intact cells. The data indicate that this effect is mediated at least in part by heterotrimeric guanosine triphosphatases. In addition, calcium/calmodulin-dependent protein kinase II appears to mediate low Ca(2+)-dependent PTH secretion from these cells.
ISSN:0013-7227
1945-7170
DOI:10.1210/endo.138.3.4971