Myocardial connexin43 expression in left ventricular hypertrophy resulting from aortic regurgitation

Intercellular conduction in the working myocardium of the mammalian heart is mediated by gap junctions composed of connexin43 or 45. Recently, it has been shown that myocardial connexin expression is malleable and may be altered with disease. To better understand myocardial conduction in left ventricular hypertrophy resulting from volume overload, we used indirect immunofluorescence microscopy to examine cardiac connexin43 expression in 10 New Zealand white rabbits with surgically induced aortic regurgitation (AR) and in 10 age-matched sham-operated controls. Animals were sacrificed at approximately 1 month or > or =2.5 years after operation. All AR animals developed eccentric hypertrophy; none evidenced heart failure. The heart-to-body weight ratios for the 1 month AR and control groups were 2.9+/-0.8 vs 1.8+/-0.2 g/kg (p < or = 0.01) while ratios for the > or =2.5 year AR and control groups were 2.4+/-0.3 vs 1.9+/-0.3 (p < or = 0.05). No significant differences in posterior wall thickness were found among any of the groups. Although the overall pattern of connexin43-like immunoreactivity was similar for all four groups, staining in the I month AR animals tended to be less than that of age-matched controls; staining was increased in the > or =2.5 year AR animals and was greater than control (p < 0.05), in which staining did not change with animal age. This disease duration-related increase differs from the long-term decrease in connexin43 expression associated with other forms of heart disease and suggests that alterations in connexin expression may play a role in the rhythm abnormalities commonly seen in AR.