Association of histamine with cerebral microvessels in regions of bovine brain

Intracerebral blood vessels of diameter< 100 μm (microvessels) were isolated from homogenates of bovine brain regions by a sieving procedure which yielded a preparation suitable for biochemical analysis. It was found that microvessels isolated from cerebral cortex grey matter had levels of endogenous histamine which were approximately 23-fold greater than the concentration found in the initial homogenate. Microvessels isolated from the striatum and hippocampus also had concentrations of endogenous histamine which were 5- to 6-fold greater than the initial homogenate. It was calculated that approximately half of the endogenous histamine in bovine cerebral cortex grey matter and one tenth of the endogenous histamine in striatum and hippocampus was associated with the microvasculature. The results of biochemical analysis of microvessel preparations from the cerebral cortex grey matter indicated that: (1) most of endogenous histamine was recovered in the crude nuclear pellet after subcellular fractionation of homogenates; and (2) the endogenous level of histamine was associated with minimal histidine decar☐ylase activity. The above features are characteristic of most cells and it is speculated that histamine in these microvessels was localized in mast cells.