Relationship between cytosolic free calcium concentration and 2-deoxyglucose uptake in adipocytes isolated from 2- and 12-month-old rats.
We have examined the relationship between insulin-stimulated 2-deoxyglucose uptake and cytosolic free calcium concentrations, [( Ca2+]i), in adipocytes isolated from 2- and 12-month-old rats. The basal rates of glucose uptake and the levels of cytosolic Ca2+ were only minimally reduced in 12-month-old animals. In contrast, insulin-stimulated glucose up-take and [Ca2+]i were significantly decreased in older adipocytes at all insulin concentrations (P less than 0.01). When the rate of glucose uptake was plotted as a function of [Ca2+]i, insulin-stimulated glucose uptake was almost identical in older and younger animals at any given level of [Ca2+]i. Similar to insulin, glyburide and K+ increased [Ca2+]i in both younger and older adipocytes. However, glyburide- and K+-elicited responses were lower in older rats (P less than 0.01). The effects of insulin, glyburide, and K+ on [Ca2+]i are mediated via voltage-dependent Ca2+ channels. Thus, the present observations suggest an impairment in either function and/or availability of the voltage-dependent Ca2+ channels in older animals. This was supported by the finding of reduced [3H]nitrendipine binding in adipocytes isolated from older animals (6.5% vs. 3.3% in 2- and 12-month-old rats, respectively; P less than 0.01). The results of these experiments indicate that the postreceptor changes in adipocyte responsiveness to insulin in aging may involve inadequate increases in [Ca2+]i. The latter probably occurs as a result of decreased availability and/or function of the voltage-dependent calcium channels.
D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism; D000375:Aging / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D003837:Deoxy Sugars / Q000378:metabolism*; D003847:Deoxyglucose / Q000378:metabolism*; D005905:Glyburide / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D007473:Ion Channels / Q000502:physiology; D007700:Kinetics; D008297:Male; D009568:Nitrendipine / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014700:Verapamil / Q000494:pharmacology
D003837:Deoxy Sugars; D007328:Insulin; D007473:Ion Channels; D009568:Nitrendipine; D003847:Deoxyglucose; D014700:Verapamil; D011188:Potassium; D005905:Glyburide; D002118:Calcium