Biosynthesis of noradrenaline in organ cultured hearts

In hearts of newborn mice, maintained in organ culture in an in vitro environment, noradrenaline levels were reduced after 24 h but subsequently recovered, reaching at three days values significantly greater than those found at birth. The increased synthesis of noradrenaline was blocked by the inhibitor of tyrosine hydroxylase, alpha-methyl tyrosine methyl ester. The site and control of noradrenaline biosynthesis in cultured newborn hearts are discussed.