Neomycin interacts with Ca 2+ sensing of normal and adenomatous parathyroid cells

Abstract

Effects of the polyvalent cationic antibiotic neomycin on regulation of the cytoplasmic Ca 2+ concentration ([Ca 2+] i) were studied in normal and adenomatous human, and bovine parathyroid cells. Parathyroid hormone (PTH) release was also measured in the bovine cells. Elevation of extracellular Ca 2+ from 0.5 to 3 mM caused biphasic increase of [Ca 2+] i and inhibition of PTH release. In low external Ca 2+ neomycin inhibited PTH release and virtually only triggered the [Ca 2+] i transient. In contrast [Ca 2+] i was lowered and PTH release stimulated by neomycin in the presence of 3.0 mM Ca 2+ or 7 mM Mg 2+. These actions of Ca 2+ and neomycin on [Ca 2+] i were qualitatively similar but less pronounced in the adenomatous than normal human parathyroid cells. Some effects of neomycin were thus similar to those induced by other cationic agents interacting with the Ca 2+ receptor mechanism on the parathyroid cell surface, whereas others may involve phospholipase C inhibition, protein kinase C activation or a direct reduction of the Ca 2+ influx.