Involvement of glutathione oxidation reduction in parathyroid hormone secretion

This study determines whether calcium affects glutathione metabolism and whether glutathione metabolism may influence parathyroid (PTH) secretion in collagenase dispersed bovine parathyroid cells. Reduced glutathione (GSH) and glutathione disulfide (GSSG) were measured fluorometrically and enzymatically while PTH secretion was determined by radioimmunoassay. The total GSH and GSSG content of parathyroid cells was found to range from 1.59 to 1.71 micrograms/mg cell protein, and this did not vary significantly with changes in extracellular calcium. An increase in the medium calcium concentration from 0.5 to 2.0 mM did, however, cause an increase in GSSG from 0.43-0.54 to 1.19-1.20 micrograms/mg protein with a concomitant decrease in GSH. The compound 2-cyclohexen-1-one was used to deplete the cells of GSH at a low-calcium medium (0.5 mM) to levels seen in high-calcium medium (2.0 mM). This treatment was found to inhibit PTH secretion in the low-calcium medium, as if the cells were incubated in high medium calcium. Both 2-cyclohexen-1-one and calcium caused a rapid decrease in reduced GSH levels and in hormone secretion. The ketone was not found to affect cellular protein synthesis, indicating that there was no nonspecific toxic effect of this treatment on the cells. These results suggest that changes in the calcium concentration of the medium affect the GSH/GSSG ratio of dispersed parathyroid cells. Changes in the GSH/GSSG ratio induced by calcium may be related to changes in PTH secretion.