Abstract

Calcium ions are modulators of many cellular processes. Small changes in cytoplasmic Ca2+ concentration affect, for example, cell proliferation, death, or gene expression. Ca2+ levels are tightly controlled in cells. Mechanisms of regulation of intracellular Ca2+ levels by intrinsic and extrinsic factors are specific to the cell type. The present project investigated the effect of hormones (insulin, estradiol, progesterone) on the level of intracytoplasmic calcium in colon cancer cells (HCT116). To determine whether hormones affect the activity of the IP3 receptor (a protein responsible for the flow of Ca2+ ions from the endoplasmic reticulum to the cytoplasm), we also determined the effect of hormones on Ca2+ levels in the presence of an inhibitor (2-aminoethyl diphenylborinate) or agonist (carbachol) of the IP3 receptor.HCT116 cells were incubated for 30 min with insulin, progesterone or estradiol in the presence of an inhibitor or agonist of the IP3 receptor. Untreated cells were the control. The intracellular Ca2+ level was then assessed using the Fluo-4 Direct Calcium Assay Kit. Since an increase in cytoplasmic calcium levels is associated with the induction of apoptosis, cell viability was also determined. Cell viability was measured using the CCK-8 assay. The results show that all hormones cause a change in intracellular calcium levels and decrease the viability of HCT116 cells as determined 30 min after the addition of hormones. After 24h incubation of HCT116 cells with hormones, cell viability increases suggesting that hormones work effectively in a relatively short period of time. Keywords: Calcium ions, IP3R, hormones