Studies on the relationship between the catecholamine distribution in the atrium and the specific granules present in atrial muscle cells: 2. Studies on the sedimentation pattern of atrial noradrenaline and adrenaline

Abstract

Studies on the function of the specific granules present in mammalian atrial muscle cells have been directed mostly to the possible role of these particles as a storage site for catecholamines, particularly noradrenaline. The availability of a fractionation method previously described, which allows us to obtain a purified specific granule preparation, has made it possible to compare the pattern of sedimentation of atrial noradrenaline and adrenaline with that of the specific granules. It was found that, after fractionation, most of the atrial noradrenaline and adrenaline liberated during homogenization was present in the microsomal fraction and in the high speed supernatant. The crude specific granule fraction and the purified specific granule subfraction contained comparatively small amounts of noradrenaline. These findings do not support the view that the specific granules are a site of storage of noradrenaline.