Seasonal influences on the functional expression of the endogenous L-type Ca2+ channels in Pleurodeles oocytes: role of cAMP?
We have investigated the seasonal regulation of the Ba current (IBa) through the L-type Ca2+ channels in Pleurodeles oocytes and its relation with the intracellular cAMP level. IBa-density remained relatively constant from January to February, increased from March to April (with a maximum increase in March) and decreased from May to July. While the permeable cAMP analogue 8Br-cAMP reduced IBa during the breeding season, it was without effect during the resting season. However, IBa recorded during the two seasons was increased by a dihydropyridine agonist Bay K 8644 and blocked by cadmium. The main conclusion is that the seasonal reduction in the L-type Ca2+ current amplitude may be correlated with a high intracellular cAMP level and may account for the inability of oocytes to mature during the resting season.
Centre de Biologie Cellulaire, Laboratoire de Physiologie Cellulaire, SN3, USTL, Villeneuve d'Ascq, France. ouadid@pop.univ-lille1.fr
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Ouadid-Ahidouch
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Van Coppenolle
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects*; D020746:Calcium Channels, L-Type; D000242:Cyclic AMP / Q000494:pharmacology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005260:Female; D009865:Oocytes / Q000502:physiology*; D018408:Patch-Clamp Techniques; D010999:Pleurodeles / Q000502:physiology*; D012621:Seasons
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases