LLC-PK1 cells, a permanent cell line of renal tubule origin, which has vasopressin (VP) receptors and an adenosine 3',5'-cyclic monophosphate (cAMP) response to VP were grown to confluence on glass cover slips and loaded for 30-45 min with fura-2. Exposure to fura-2 did not affect cell viability (> 99%), K+, or ATP levels. Free cytosolic Ca2+ (Ca(f)) was estimated spectrofluorometrically on washed cover slips. Basal levels averaged 73 ± 3 nM. Peak Ca(f) levels induced were: 10-8 M VP - 128 ± 24 nM, 10-7 M VP - 301 ± 51 nM, 10-6 M VP - 537 ± 117 nM. Peak Ca(f) after 10-6 M VP was reached in 42 ± 5 s, followed by a return toward basal levels. Addition of a second dose of 10-6 M VP following an initial dose of 10-6 M VP did not raise Ca(f). Chelation of medium Ca2+ with ethylene-glycol-bis(β-aminoethylether)-N,N'-tetraacetic acid just prior to 10-6 M VP did not reduce the response of Ca(f) (peak of 359 ± 53). In contrast to VP, 10-6 M calcitonin and PTH did not significantly increase Ca(f). The response to 10-6 M VP was not significantly modified by prior prostaglandin E2 (3 μM) or dibutyryl-cAMP (100 μM). The response to 1-desamino-8-D-arginine vasopressin was less than that to VP. However, studies with VP-receptor antagonists did not allow definitive delineation of receptor type. These data evidence for VP-induced increases of Ca(f) via release from intracellular stores in a renal epithelial cell.
|Journal||American Journal of Physiology - Renal Fluid and Electrolyte Physiology|
|Issue number||6 (20/6)|
|Publication status||Published - 1986 Jan 1|
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