Activation of protein kinase A and protein kinase C mediates the depolarising effect of LH in ovine cumulus-corona cells.
We have studied the changes in membrane potential induced by LH in cumulus and granulosa cells isolated from sheep antral follicles. The investigation was carried out by using a non-invasive technique based on the use of a membrane potential sensitive probe, bis-oxonol. The membrane potential of mural granulosa cells was totally unaffected by LH, while that of cumulus or corona cells showed a marked depolarisation, starting 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 kinase C (PKC) in mediating the effect of LH was studied. The selective activation of PKA or PKC induced in cumulus-corona cells a rapid hyperpolarisation due to increased Cl and K conductance respectively. By contrast, the simultaneous activation of the two kinases induced a rapid membrane depolarisation due to the progressive decrease in K conductance. The activation of each kinase or their combined stimulation did not induce any change in the membrane potential of mural granulosa cells. These data demonstrated that LH has a depolarising effect regionally circumscribed to cumulus-corona cells and that this depolarisation depends on a reduction of K conductance caused by the activation of PKA and PKC.
Mattioli
M
M
Istituto di Fisiologia Veterinaria, Università degli Studi di Teramo, Italy.
Barboni
B
B
Gioia
L
L
D000818:Animals; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects / Q000502:physiology; D007986:Luteinizing Hormone / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D006080:Ovarian Follicle / Q000187:drug effects / Q000502:physiology*; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D012756:Sheep
D007986:Luteinizing Hormone; D011494:Protein Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C