Effects of endothelin-1 on bovine parathyroid cells

Endothelin-1 (ET-1) is synthesized and released by parathyroid epithelium. The effects of endothelin isopeptides were studied in clonal bovine parathyroid endothelial (BPE) cells. BPE cells did not produce ET-1, but showed ETA receptors (Kd = 0.1 +/- 0.02 nM, mean +/- SE). ET-1 (10(-8)10(-11)M) increased the intracellular calcium ion concentration ([Ca2+]i) in BPE cells, while endothelin-3 (ET-3) was ineffective. The increase in [Ca2+]i was less sustained in the absence of extracellular Ca2+ ions. Moreover ET-1 induced phospholipase C (PLC) activation, as demonstrated by the increase in inositol trisphosphate. Cell growth was not affected by ET-1 in a wide range of concentrations. The present findings demonstrate: 1) BPE cells possess ETA receptors; 2) the peptide activates PLC and increases cytosolic [Ca2+]i via both a release of Ca2+ ions from intracellular calcium pool(s) and an influx of the cation from the extracellular milieu. A possible role of ET-1 as a paracrine factor in parathyroid tissue can be hypothesized.