Urotensin II lowers cytoplasmic free calcium concentration in goby enterocytes: measurements using quin2

A technique is described for the measurement of cytoplasmic free calcium concentration ([Ca2+]c) in a suspension of goby intestinal epithelial cells using the fluorescent probe quin2. For 18 cell suspensions, [Ca2+]c was determined to be 142 +/- 14 nM. The caudal neurosecretory peptide urotensin II at 10(-7) to 10(-6) M concentration reduced [Ca2+]c by 20-50%. Together with previous findings linking the calcium-calmodulin system with the stimulation of Na+ and Cl- absorption in this tissue, it appears that alterations in cytoplasmic Ca2+ may mediate urotensin II-induced stimulation of ion transport.