[Hormones and the levels of humoral regulation]

The problems on the place of hormones secreted by "classical" endocrine glands, on their relationship with other compounds that possess physiological activity, criteria that determine the definition "hormone" are considered in this article. The conception about the levels of the humoral regulatory systems that are organized and formed during phylogenesis and ontogenesis and provide a consecutive increase in their complexity and mobility of adaptation to changes of environment and internal conditions are substantiated on the basis of numerous data. The metabolites that are products of nonspecific activity of any cell of the multicellular organism form the first and simplest level of humoral regulatory organization. The next (second) level of humoral organization is also formed by chemically simple substances. However, these substances are specialized products of the secretory activity of cells and exert potent influence on the physiological processes. Neuroamines and regulatory peptides are applied to these agents, in the first place. They arise simultaneously and jointly at the first stage of ontogenesis. The distinctive characters of the third level of the humoral regulation are increased and complication of the regulatory activity conditioned by cooperative influences of humoral agents produced by single secretory elements situated outside the classical endocrine glands. The chemically and originally different substances causing predominantly local effects are attributed to these physiologically active substances. Their participation in general adaptive reactions as well as inclusion of classical hormones into hierarchy of humoral regulation signify the formation of the forth regulatory level that provides realization of general homeostatic reactions peculiar to the whole organism.(ABSTRACT TRUNCATED AT 250 WORDS)