AGE-RELATED LEVELS OF URINARY FREE CORTISOL IN THE TREE SHREW

There are still controversies concerning the effect of aging on the ba sal glucocorticoid concentration in mammals, including humans. Some st udies reported an elevated glucocorticoid concentration in older subje cts, while other reports showed no increases with age. These discrepan cies may be caused by different experimental designs, gender differenc es, or varying sampling time points. The hulk of animal studies report ing increases of glucocorticoids with age were performed in rats. The present study was designed to investigate the impact of age on adrenoc ortical activity in a non-rodent mammalian species, tree shrews (Tupai a belangeri). We analyzed the basal urinary free cortisol concentratio n in the morning urine of male tree shrews in different age groups. Im mediately after birth, a large variation in basal urinary free cortiso l concentration (10-818 pg/mu mol crea) has been observed. Between 21- 40 day of age, the urinary cortisol concentration was low (32.7 +/- 5. 6 pg/mu mol crea) and increased steadily during puberty until adulthoo d (201-500 days; 161.8 +/- 15.1 pg/mu mol crea). Thereafter, no furthe r rise in basal urinary free cortisol concentration was found with inc reasing age and after reaching senescence (7-8 years). (C) 1998 Elsevi er Science Inc.