Developmental regulation of the gradient of cftr expression in the rabbit heart

Gradients of ion channels across the left ventricular free wall of the heart have been found for a number of repolarizing ion channels. Amongst these are the cAMP-activated chloride channels encoded by cftr. In this report, we show that the epicardial (higher) to endocardial (lower) gradient of cftr mRNA found in adult rabbit hearts is not present in embryonic hearts. The gradient starts to develop shortly after birth, and over a period of 5-6 weeks increases to the levels found in the adult. This is the first report of the developmental regulation of any cardiac ion channel mRNA gradient.