Gamma-glutamyl transpeptidase and acetylcholinesterase activities in brain capillaries of cholesterol-fed rabbits.

Cerebral microvascular endothelium, the constituent cell of the blood-brain barrier, is enriched in the enzyme gamma-glutamyl transpeptidase (GGT). This enzyme plays a role in the regulation of amino acid uptake and transport, and in the gamma-glutamylation of serotonin, dopamine and norepinephrine. Recent studies have demonstrated that GGT activity is modulated by cholinergic-adrenergic agonists. The levels of the acetylcholine-catabolizing enzyme acetylcholinesterase (AChE), may therefore be related to the modulation of the GGT activity. In this study, the activities of GGT and AChE in microvessel-enriched fractions were assayed after feeding of rabbits a high cholesterol diet. A 21% decrease of GGT activity and a 44% increase of AChE activity appeared at the end of dietary treatment.