Mechanisms of disturbance of catecholamine synthesis in the adrenals of physically fatigued rats

Abstract

The ability of the adrenals to synthesize catecholamines in the presence of various substrates was investigated in vitro. Experiments were carried out on rats under normal conditions and after swimming for 8 h. In the physically fatigued animals the conversion of noradrenalin, DOPA, and tyrosine, added in vitro, into catecholamines was inhibited, on the basis of which depression of the activity of phenylethanolamine-N-methyl-transferase, dopa decarboxylase and, possibly, tyrosine hydroxylase was postulated. After the end of swimming, and in the presence of L-tyrosine as substrate, noradrenalin synthesis was activated first (on the second day), and this was followed by gradual restoration (on the 7th day) of normal adrenalin synthesis. In rats trained for two months, in response to swimming for 8 h the degree of depression of catecholamine synthesis in the adrenals was much smaller than in untrained rats.