title: Impaired adaptive receptor regulation: an index of aging?
abstract: Many neuroendocrine functions are altered in old animals and their study may represent important steps in the understanding of the mechanisms of aging. A deeper insight, however, can be achieved by investigating the responsiveness to stimuli, which may reveal alterations not evident in the unstimulated conditions. At this level of study, many of such impairments have been found to be caused by receptor changes. In the present paper a third level of study is suggested in order to gain evidence of some remote failure of adaptive processes strictly linked to intimate mechanisms of aging. As at the second level of study different receptor characteristics can frequently be found at the basis of age-related alterations of biological responsiveness, at the proposed third level altered capacity of receptor regulation may be hypothesized as responsible for altered cell adaptation following hormone and drug stimuli. Experimental data are given which support this view. The possibility that receptor regulation may be used as an index of aging is suggested. This hypothesis leads to the problem of judging the validity of biological parameters deputed to represent good indices of aging. In order to solve this problem, the potential use of a mathematical model of mortality kinetics is discussed.
mesh_terms: D000222:Adaptation, Physiological; D000367:Age Factors; D000375:Aging; D000818:Animals; D005260:Female; D006801:Humans; D007700:Kinetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008954:Models, Biological; D009026:Mortality; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D013965:Thyroidectomy
chemical_list: D011943:Receptors, Adrenergic, beta