title: Altered cellular heterogeneity as a possible mechanism for the maintenance of organ function in senescent animals.
abstract: We tested the hypothesis that an alteration in the functional heterogeneity of cell populations (i.e., changes occurring in sensitivity and responsiveness to external stimuli among individual cells) may be a mechanism by which some organs are able to resist age-related decrements in function. To this end, changes in cytoplasmic free calcium concentration ([Ca2+]i) following glucose stimulation of individual pancreatic beta cells isolated from male F344 rats of ages 6, 12, and 26 mo were used as a model for evaluating responsiveness and sensitivity. Changes in [Ca2+]i of individual beta cells were monitored using fura-2 microspectrofluorimetry. No differences were observed in [Ca2+]i or in insulin secretion per beta cell among the age groups at any of the glucose concentrations. However, the percentage of beta cells that were responsive to a stimulatory glucose concentration (> 5.5 mM) was significantly greater in islets from the 26-mo-old rats (76%) as compared to the 6- and 12-mo-old animals (63% and 65%, respectively). Of the responsive beta cells, a significantly greater percentage of those from the 26-mo-old rats (72%) responded at the lowest stimulatory glucose concentration (7.5 mM) as compared to the 6- and 12-mo-old animals (58% and 60%, respectively). These data suggest that the maintenance of organ function in older rats at a level comparable to that of younger animals may be accomplished, in part, by an increase in the percentage of cells that are responsive to stimuli and/or by an increase in the sensitivity of the responsive cells.
authors.affiliation: Department of Nutrition, University of California, Davis, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Ruhe
authors.forename: D L
authors.initials: DL
authors.lastname: Curry
authors.forename: R B
authors.initials: RB
authors.lastname: McDonald
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D009994:Osmolar Concentration; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D007328:Insulin; D005947:Glucose; D002118:Calcium