Isolated brain microvessels: preparation, morphology, histamine and catecholamine contents

Area of Science:

• Neuroscience
• Vascular Biology
• Biochemistry

Background:

• Brain microvessels play crucial roles in regulating cerebral blood flow and maintaining the blood-brain barrier.
• Understanding the biochemical composition of microvessels is essential for studying neurological disorders and drug delivery.
• Previous methods for isolating brain microvessels were often time-consuming and resulted in cellular damage.

Purpose of the Study:

• To establish a rapid and efficient method for preparing pure parenchymal microvessels from mammalian brains.
• To characterize the cellular components and biochemical content (histamine, catecholamines) of isolated brain microvessels.
• To investigate potential age-dependent and hypertension-related alterations in microvessel histamine levels.

Main Methods:

• A novel technique for the rapid isolation of parenchymal microvessels from rat, rabbit, and bovine brains.
• Light and electron microscopy were employed to assess the integrity of endothelial and smooth muscle cells and to detect cellular contaminants.
• Histamine content was measured in microvessel extracts, and catecholamine (CA) levels were determined using a sensitive radioenzymatic assay.

Main Results:

• Isolated microvessels exhibited intact smooth muscle and endothelial cells with minimal neutrophil contamination.
• Electron microscopy revealed electron-dense granules in the adventitial space, suggesting the presence of mast cells, further supported by histamine detection.
• Age-dependent variations in histamine content were observed, along with elevated histamine levels in microvessels from hypertensive rats.
• Total catecholamine content was low (< 0.35 µg g⁻¹), with norepinephrine as the predominant catecholamine, and a high dopamine-to-norepinephrine ratio was noted in rat and bovine brain microvessels.

Conclusions:

• The described method allows for the rapid and high-purity isolation of brain microvessels suitable for biochemical analysis.
• The presence of mast cells and measurable levels of histamine and catecholamines highlight the complex cellular and neurochemical environment of brain microvessels.
• The findings suggest that microvessel histamine content is influenced by age and hypertension, warranting further investigation into the role of mast cells in cerebrovascular regulation and disease.