Aim: Potassium currents are known to be implicated in cardiac remodelling during pregnancy, yet little is known about their hormonal regulation in this condition. Aldosterone, the hormone acting through its mineralocorticoid receptors (MRs), has been shown to decrease potassium currents in cultured cardiomyocytes. Moreover, aldosterone levels are increased in human and rat pregnancy. Our aim is therefore to examine the possible role of MRs in potassium current adaptations, in left ventricular cardiomyocytes, during rat pregnancy.

Methods: 

Pregnant rats, one day before parturition, were compared to non-pregnant ones (NP). One group of pregnant rats was treated with potassium canrenoate (20 mg/kg/day), a MRs antagonist, in drinking water for the last seven days of pregnancy. Patch clamp technique was applied to study potassium currents. Results: Pregnancy induced a decrease in the density of the transient outward potassium currents, I_to: 5.2 ± 0.4 pA/pF (n = 11) vs. 8.8 ± 0.8 pA/pF in NP (n = 20), at +50mV; p < 0.05. MR blockade prevented the lowering of I_to: 7.5 ± 1.3 pA/pF (n = 10), p < 0.05. Our results also uncovered a decreased density of the inwardly rectifying potassium current, I_K1, in pregnancy: -7.5 ± 1.3 pA/pF (n = 14) vs.-13.8 ± 1.8 pA/pF in NP (n = 14), at -120 mV; p < 0.05. MR blockade had a tendency to further decrease I_K1 density: -4.1 ± 0.6 pA/pF (n = 10).

Conclusions: 

Our data indicate that MRs are implicated in the adaptation of potassium currents during pregnancy. Understanding the regulation of ionic currents during pregnancy is crucial to determine their possible variations in pathological conditions, such as gestational hypertension, where aldosterone blood levels are decreased.