Effects of Adrenergic Stimulation on Postnatal Development and Calcium Current in Newborn Rat Cardiomyocytes in Primary Culture

With a primary culture of ventricular cardiomyocytes from newborn rats as an in vitro model, the long-term effects of norepinephrine (NE) on hypertrophic postnatal development and the I/V properties of L-type calcium currents were investigated with the whole-cell configuration of patch-clamp technique. These effects of NE also were tested in the presence of propranolol (P). Compared with mean values obtained in control conditions, the measurement of cell membrane capacitance (Cm) as an index of cell growth demonstrated that Cm was increased by 12, 35, and 42% after 1, 3, and 6 days, respectively, of treatment with 2 μM NE. Similar increases were observed when propranolol(2 μM) was added to the NE treatment, suggesting that growth potentiation could be attributed to the α-adrenergic effect of NE. Under control conditions, the L-type calcium current (ICa-L) density did not alter with the age of the culture. However, in the presence of NE, ICa-L density increased significantly compared with control conditions at the same stage of culture and was also significantly increased after 3 and 6 days of NE treatment when compared with ICa-L density after 1 day of NE treatment. Similar results were obtained in the presence of propranolol. These results show that the growth and functional properties of neonatal cardiomyocytes in primary culture can be regulated by catecholamines and demonstrate that these regulatory effects were achieved through activation of α-adrenoceptors.