CHOLINESTERASES IN THE BLOOD OF MAN

Localization and characterization of cholinesterase in subcellular fractions of rat brain and beef pituitary

Fresh rat brains and fresh anterior and posterior pituitary glands of beef were separated by differential centrifugation into subcellular fractions, characterized on the basis of sedimentation and succinic dehydrogenase activity. Cholinesterase activity was measured by both manometric and colorimetric methods, the results of which were comparable. Cholinesterase activity of rat brain was found mainly in the microsome and supernatant fractions. It was quite uniformly distributed in all subcellular fractions of both anterior and posterior pituitary. Comparisons of the relative rates of hydrolysis of acetylthiocholine and butyrylthiocholine, and of inhibition by eserine, indicated that brain contains a much higher percentage of acetylcholinesterase than do both lobes of the pituitary, which contain relatively low concentrations of the specific enzyme. Total cholinesterase activity and its sensitivity to inhibition by eserine in the posterior pituitary were found to be midway between those of the anterior lobe and of the brain, from which the posterior pituitary was derived during embryological development.

Pharmacological actions of pure muscarine chloride

The action of chromatographically pure crystalline muscarine chloride, prepared from Amanita muscaria, has been compared with acetylcholine chloride (ACh) on a number of different organs from a variety of species. Muscarine caused spasm in vivo and in vitro of muscles of the gut, uterus, urinary bladder, and bronchus. It also caused contraction of the horse ureter and carotid artery chain in vitro and slowed the isolated auricles of the guinea-pig and rabbit, and the frog heart.Muscarine caused a drop in blood pressure, although in vitro it produced either constriction or dilatation of the blood vessels of the rabbit ear.All these actions resembled those of acetylcholine, though muscarine was usually more potent. Muscarine effects were readily prevented by atropine sulphate. It had a slight action on the frog rectus abdominis muscle, causing a contracture at high concentrations. Muscarine was destroyed neither by pepsin nor by boiling at any pH. It was inactive by mouth in a monkey in a quantity many times that which would cause poisoning by ingestion of Amanita muscaria in the human being. Muscarine neither inhibited nor was hydrolysed by either true- or pseudo-cholinesterase. Muscarine chloride did not cause paralysis of the neuromuscular junctions of the rat diaphragm or of the cat gastrocnemius.