Intracellular free calcium in response to oxytocin in pig endometrial cells

Intracellular free calcium concentration ([Ca2+](i)) in response to oxytoci n (OT) was studied in stromal, glandular epithelial and luminal epithelial cells obtained from the endometrium of gilts 16 days post-estrus. The ampli tude of increased [Ca2+](i) in response to 100 nM OT was greatest in stroma l cells, intermediate in glandular epithelial cells and not evident in lumi nal epithelial cells. During continuous OT administration, stromal cells re sponded initially with a synchronous spike of [Ca2+](i) that did not requir e extracellular Ca2+ and then displayed spontaneous asynchronous [Ca2+](i) spikes that required extracellular Ca2+. Each cell possessed its own charac teristic response. Increasing concentrations of OT induced an increasing pe rcentage of stromal cells responding, with some cells having nearly equal [ Ca2+](i) responses at all concentrations and others having graded [Ca2+](i) responses as the concentration of OT increased. These results are consiste nt with the proposed mechanism of OT action in pig endometrium involving ac tivation of phosphoinositide-Ca2+ signaling pathway. (C) 1999 Elsevier Scie nce Ireland Ltd. All rights reserved.