Seasonal influences on the functional expression of the endogenous L-type Ca2+ channels in Pleurodeles oocytes: role of cAMP?

Abstract

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.