The effects of aging on leukocyte glucocorticoid receptor concentration and response to dexamethasone in dogs

Abstract

Glucocorticoid receptor concentration (GR) was determined in mononuclear (MNS) and polymorphonuclear (PMNS) cells isolated from 8 aged and 9 young male dogs. In addition, leukocyte responses to dexamethasone (0.1 mg kg21 iv) and plasma glucose concentration were also measured. The GR in MNS and PMNS was higher ðp , 0:05Þ in young dogs (6.64 ^ 0.57 and 7.04 ^ 0.29 fmoles £ 106 cells, respectively, versus 4.40 ^ 0.24 and 5.06 ^ 0.33 fmoles £ 106 cells, respectively, in aged dogs). The maximum increase in neutrophils (D NEU) was lower ðp , 0:05Þ in aged dogs 6003.38 ^ 1398.5 £ 106 versus 11168.67 ^ 1863.16 £ 106 cells l21 in young dogs. The maximum decrease in lymphocytes (D LYM) was lower ðp , 0:05Þ in aged dogs 550 ^ 56.75 £ 106 cells l21 versus 1825.89 ^ 313.1 £ 106 cells l21 in young dogs. In young dogs, significant ðp , 0:05Þ correlations between GR in PMNS and D NEU ðr ¼ 0:80Þ and between GR in MNS and D LYM ðr ¼ 0:76Þ were observed. In aged dogs, these correlations were not significant. The lower GR value and the lack of correlation between this parameter and its respective D in aged dogs suggest that changes in leukocytes responsiveness to glucocorticoids is occurring during the aging process.