Characteristics of electrophysiology and effects of ouabian on transient outward potassium current and L-type calcium current of left atrium posterior wall of rabbits

Objective To investigate properties of electrophysiology and effects of ouabain on transient outward potassium current (I to ) and L-type calcium current (I Ca-L ) of left atrium posterior wall (LAPW) and left atrium appendage tissue (LAA) of rabbit, it could provide the scientific explanations that LAPW and ouabain could enhance atrial fibrillation (AF) vulnerability via increasing electrophysiological heterogeneity and electrical remodelling of different region of left atrium in rabbits. Methods Atrial myocytes coming from LAPWs and LAAs of rabbits perfused via vitro heart perfusion system were obtained by enzymatic dissociation. The whole-cell patch-clamp technique was used to assess effects of ouabain on I to and I Ca-L . The current-voltage (I-V) curves of I to and I Ca-L on LAPW and LAA myocytes were fitted before and after of ouabain administration. Results (1) With holding potential −50 mV and commanding potential +50mV, the current densities of LAPW I to were decreased slightly less than that of LAA I to in control groups in control groups (p>0.05). After administration of ouabain. the current densities of LAPW I to were significantly larger than that of LAA I to ((10.97±0.58) pA/pF vs (9.39±0.83) pA/pF, p to was gently lowered to I∼V curve of LAA I to in control groups. But with perfusion of ouabain, the I∼V curve of LAPW I to opposed to I∼V curve of LAA I to was significantly changed from the bottom to the top with same upward direction. (2) At voltage clamp protocol of I Ca-L , the current densities of LAPW I Ca-L were markedly decreased compared with that of LAA I Ca-L in control groups (p Ca-L at +20 mV was obviously increased to that of LAA I Ca-L ((−11.13±0.99) pA/pF vs (−8.86±0.51) pA/pF, p Ca-L was arranged the bottom of all I∼V curves of I Ca-L . The I∼V curve of LAPW I Ca-L , but through effects of ouabain, was completely upgraded to the top of other I∼V curves of I Ca-L . However, all shapes and directions of current peak of I∼V curves of I Ca-L were not changed between the control group and ouabain groups. Conclusion The distribution properties of I Ca-L have significant difference on LAPW of rabbit. Ouabain could accentuate the electrophysiological heterogeneity and electrical remodelling of I to and I Ca-L in LAPW of rabbits. It might contribute trigger and persistence factors to AF vulnerability.