M. Mattioli et al., ACTIVATION OF PROTEIN-KINASE-A AND PROTEIN-KINASE-C MEDIATES THE DEPOLARIZING EFFECT OF LH IN OVINE CUMULUS-CORONA CELLS, Journal of Endocrinology, 150(3), 1996, pp. 445-456
We have studied the changes in membrane potential induced by LH in cum
ulus and granulosa cells isolated from sheep antral follicles. The inv
estigation was earned out by using a non-invasive technique based oil
the use of a membrane potential sensitive probe, bis-oxonol. The membr
ane potential of mural granulosa cells was totally unaffected by LH, w
hile that of cumulus or corona cells showed a marked depolarisation, s
tarting 2-3 min after the addition of the hormone and plateauing after
5-10 min. None of the cells tested reacted to FSH. In the second part
of the experiment the role of protein kinase A (PKA) and protein kina
se C (PKC) in mediating the effect of LH was studied. The selective ac
tivation of PKA or PKC induced in cumulus-corona cells a rapid hyperpo
larisation due re, increased Cl and K conductance respectively. By con
trast, the simultaneous activation of the two kinases induced a rapid
membrane depolarisation due to the progressive decrease in It conducta
nce. The activation of each kinase or their combined stimulation did n
ot induce any change ill the membrane potential of mural granulosa cel
ls. These data demonstrated that LH has a depolarising effect regional
ly circumscribed to cumulus-corona cells and that this depolarisation
depends on a reduction of K conductance caused by the activation of PK
A and PKC.