Carbachol increases intracellular free calcium concentrations in human granulosa-lutein cells

We investigated whether the stimulation of human granulosa-lutein
cells with muscarinic and nicotinic receptor agonists can cause
increases in intracellular free calcium (Ca2+), using Fura-2
microfluorimetry. The addition of carbachol (a non-selective
muscarinic and nicotinic receptor agonist) to cultured human
granulosa-lutein cells increased intracellular free Ca2+ levels.
Concentrations as low as 10 nmol/l were effective. In contrast,
nicotine did not evoke elevations of intracellular free Ca2+. Basal
Ca2+ levels ranged around 70–140 nmol/l and maximal,
carbacholinduced peaks reached 1·1 µmol/l. The carbachol-induced
Ca2+ signal was abolished after preincubation of the cells with the
muscarinic receptor antagonists quinuclidinyl benzilate or
atropine, but it was not affected by removal of extracellular Ca2+.
Further evidence for the involvement of intracellular Ca2+ stores
is provided by experiments in the absence of extracellular Ca2+.
While thapsigargin (a blocker of ATP-driven Ca2+ uptake by
intracellular stores) and ionomycin (an ionophore by which Ca2+ is
released from intracellular stores) evoked small Ca2+ transients,
cells pretreated with these agents did not respond to carbachol any
more. These data suggest the presence of a functional muscarinic
receptor on human granulosa-lutein cells and imply the involvement
of intracellular Ca2+ stores during the cellular response. These
results also suggest the participation of the nervous system,
acting through muscarinic receptors, in the control of the function
of human granulosa-lutein cells.