Open AccessEffect of Aging on Norepinephrine and Phenylephrine Stimulated Lactate Production by White Adipocytes
Author(s) -
Faintrenie G.,
Géloën A.
Publication year - 1997
Publication title -
obesity research
Language(s) - English
Resource type - Journals
eISSN - 1550-8528
pISSN - 1071-7323
DOI - 10.1002/j.1550-8528.1997.tb00649.x
Subject(s) - phenylephrine , norepinephrine , endocrinology , medicine , white (mutation) , chemistry , blood pressure , biochemistry , dopamine , gene
We have recently demonstrated that adipose tissue can produce lactate independently of lipolysis in insulin‐resistant rats and that lactate production depends on aj‐adrenergic stimulation. In this study, we have investigated the influence of aging on norepinephrine‐and‐phenylephrine‐stimulated lactate production and glycerol production. We showed that basal and norepinephrine stimulated lactate production were significantly increased in adipocytes isolated from old vs. young rats (0.165 ± 0.006 vs. 0.055 ± 0.008 for basal and 0.576 ± 0.026 vs. 0.277 ± 0.019 umol lactate/10 6 cell/15 minutes for norepinephrine‐stimulated lactate production, respectively, p <0.05). The sensitivity of lactate production to norepinephrine stimulation in adipocytes isolated from old rats was significantly decreased (EC 50 =523 ± 63.7 vs. 46.7 ± 6.34 nM, respectively, p ><0.05). Maximal lactate production obtained with norepinephrine and phenylephrine was not significantly different in either group (0.576 ± 0.026 vs. 0.520 ± 0.036 in old and 0.277 ± 0.019 vs. 0.275 ± 0.017 umol/10 6 cell/15 minutes in young rats, respectively, ns). Lactate production by adipocytes isolated from old rats were significantly less sensitive to phenylephrine stimulation compared with young (EC 50 =3.67 ± 1.16 vs. 0.07 ± 0.01 nM, respectively, p <0.05) indicating that the effects of aging on norepinephrine and phenylephrine stimulation were probably induced by a decreased number of α 1 ‐adrenoceptors. The mechanism by which aging increases adipocyte responsiveness of lactate production has not yet been elucidated.