Effect of Aging on Urinary Kallikrein Excretion in Normal Subjects and Patients with Essential Hypertension

Abstract

The effect of aging on urinary kallikrein excretion (U_kalV) was investigated in normal subjects (n=54, 11 to 88 y.o.) and patients with essential hypertension (n=37, 17 to 82 y.o.). Urinary sodium (U_NaV), potassium (U_KV), creatinine (U_CrV) and aldosterone excretion (U_AldV) were also measured in these subjects.
U_NaV and U_KV were not significantly changed with age in both normal subjects and hypertensive patients. In normal subjects, U_KalV (r=0.45, p<0.001), U_AldV (r=-0.58, p<0.01) and U_CrV (r=-0.40, p<0.005) significantly decreased with age. U_KalV was positively correlated with both U_AldV (r=0.44, p<0.001) and U_CrV (r=0.56, p<0.001). In contrast the hypertensive patients showed significant decrease with age in U_AldV (r=-0.36, p<0.05) and U_CrV (r=-0.44, p<0.01), but no significant change in U_KalV and no significant correlation between U_KalV and U_AldV or U_CrV was observed. In the subjects below 60 years there was no significant difference in the value of U_KalV between normal subjects and hypertensive patients, but the hypertensive patients above 60 years excreted more urinary kallikrein than normal subjects of the same age group (p<0.05).
In conclusion the age-related decrease of U_KalV in normal subjects might be due to the reduced activity of the renin-angiotensin-aldosterone system and renal blood flow caused by aging. It remains elucidated whether the absence of the age-related decrease of U_KalV in hypertensive patients is related to the pathogenesis or pathophysiology of essential hypertension.