Effects of parathyroid hormone-related peptide on the large conductance calcium-activated potassium channel and calcium homeostasis in vascular smooth muscle cells.

AbstractAim: To demonstrate the impact of the parathyroid hormone–related peptide (PTHrP) on the large conductance calcium–activated potassium (BKCa) channels in vascular smooth muscle cells (VSMC) and hyperpolarization of the cell membrane and its dependence on calcium. Materials and Methods: VSMC were isolated from rat aorta and further subcultured. Four experiments were conducted in calcium–release measurements and each of them consisted of a control group, PTHrP, chemical substance, and PTHrP + chemical substance. Chemical substances used were: iberiotoxin, xestospongin C, xestospongin D, and thapsigargin, respectively. Fura–2 imaging was used to determine changes in calcium release of VSMC. In membrane–potential experiments, groups were designed similarly to the Fura–2 imaging experiments: iberiotoxin, BAPTA, and xestospongin D were added, in respective order. Changes in the membrane potential were examined using the fluorescence dye (DiBAC). Results: Given in a dose between 0.01 and 1.0 μmol/L, PTHr...