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Patch clamping studies using non-cardiomyocytes revealed that the human connexin40 mutations P88S, G38D, and A96S are associated with reduced gap junction conductances compared to wild type connexin40 (wtCx40). Their effects within myocytes however are unclear. We aimed to characterise P88S, G38D, and A96S after expression in rat hearts and primary cardiomyocyte cultures.Adult Sprague-Dawley rat atria were transduced with a lentivector containing a transgene encoding wtCx40, P88S, G38D, A96S, or eGFP (n=6 per transgene). Electrophysiology studies (EPS) were performed just prior to and 7 days after surgery. Left atria were assessed for connexin expression, mRNA levels, inflammation and fibrosis. Primary cardiomyocyte cultures were also transduced with the abovementioned vectors (n=6 per transgene) and monolayer conduction velocities (CV) and protein expression were assessed at 96hours.At day 7 EPS, P wave and induced atrial fibrillation (AF) durations were significantly longer in the mutant groups when compared to wtCx40 controls (p0.05). There were no significant differences in inflammation, fibrosis, or heart to body weight ratios. Monolayer CV's were reduced in the A96S group compared to the wtCx40 group. While similar to wtCx40 controls, P88S velocities were reduced compared to eGFP controls. G38D monolayers possessed spontaneous fibrillatory activity and could not be paced. Immunofluorescence revealed that P88S and G38D reduced native connexin43 myocyte coupling while A96S appeared to co-localise with connexin43 in gap junctions. Connexin43 mRNA levels were similar between groups.The A96S, G38D, and P88S Cx40 mutations slow conduction and increased the propensity for inducible AF.

myocytes of diabetic rabbits as indicated by increase in co-immunoprecipitation (co-ip) of p47phox with p22phox subunits of NADPH oxidase and in glutathionylation of endothelial nitric oxide synthase (eNOS) (58± 6%) known to uncouple eNOS. Diabetes reduced co-ip of 1 Na+-K+ pump subunit with glutaredoxin 1 (Grx1) that reverses glutathionylation of proteins. Consistent with this, glutathionylation of the 1 subunit was increased (52± 9%) and electrogenic Na+-K+ pump current measured in voltage-clamped myocytes was reduced (0.26± 0.04 vs 0.44± 0.04 pA/pF). Administration of CL (40 g/kg/h) had no effect on glucose or insulin levels but reduced lipid peroxidation. It also reduced p47phox/p22phox co-ip, reduced glutathionylation of eNOS (51± 1%) and 1 pump subunit (74± 13%), increased Grx1/ 1 pump subunit co-ip and increased Na+-K+ pump current (0.6± 0.1 vs 0.26± 0.04 pA/pF). Diabetes inducedmolecular remodelling in anoxidative pathway that is determinant of the functionally important oxidativemodification of Na+–K+ pump. Reversal of these changes by 3 AR stimulation suggests that 3 ARagonists may have cardiovascular protective effects in diabetes. http://dx.doi.org/10.1016/j.hlc.2013.05.239

M.Carrington1, S.Stewart 1,∗, T.Marwick2, P.Davidson3, P. Macdonald4, J. Horowitz 5, H. Krum6, P. Newton3, C. Reid6 1 Baker IDI Heart and Diabetes Institute, Australia 2 University of Queensland, Australia 3 University of Technology/Curtin University, Australia 4 St. Vincent’s Hospital and Victor Chang Cardiac Research Institute, Australia 5 The Queen Elizabeth Hospital and University of Adelaide, Australia 6 Monash University, Australia