Comparative regional and subcellular distributions of histamine and norepinephrine in the hearts of rats, mice, guinea pigs, rabbits, and dogs.

The patterns of distribution of histamine and norepinephrine among the 4 chambers of the heart of rats, guinea pigs, and rabbits and among 15 portions of the dog heart were quite similar, except for the coronary ring of the dog, which was disproportionately high in histamine. In whole mouse hearts the separate chambers were not assayed; in the whole heart, the contents of the 2 amines did not correlate. The subcellular distribution of histamine in the rat and guinea pig heart was different from that of norepinephrine. Histamine was mostly associated with mast cell-like granules. Toluidine blue-staining granules of 2 widely different densities were found.