The influence of adrenoceptor activity on cell proliferation in colonic crypt epithelium and in colonic adenocarcinomata

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Abstract
The effects of chemical sympathectomy and of the injection of amines or amine-receptor blocking drugs on cell proliferation in colonic crypts and in dimethylhydrazine-induced colonic carcinomata is examined in rats using a stathmokinetic technique. In animals which were chemically sympathectomized by injection of 6-hydroxydopamine cell proliferation essentially ceased in the colonic crypts but continued at a normal rate in the tumours. Stimulation of .alpha.-adrenoceptors by metaraminol, a drug with properties similar to noradrenaline [norepinephrine], caused acceleration of cell proliferation in colonic crypts but not in tumors. Blockade of .alpha.-adrenoceptors by phentolamine inhibited cell proliferation in crypts but not in tumors. Injection of adrenaline [epinephrine], predominantly a .beta.-adrenergic agonist, inhibited cell proliferation in the tumors but not in colonic crypts whereas blockade of .beta.-adrenoceptors by propranolol accelerated cell proliferation in tumors but not in colonic crypts. It is postulated that cell proliferation in the crypts of Lieberkuehn in rat colon resembles that in rat jejunum in being controlled by the autonomic nervous system. Tumor cell proliferation does not appear to be subject to such regulation.