Effect Of Age On Renal Functional And Orthostatic Vascular Response In Healthy Men

Abstract

1. Few studies have been reported concerning the effect of ageing on renal functional and vascular responses to various stresses during ordinary life. In the present study, we examined the effect of age on changes in renal sodium handling and renal vascular resistance (RVR) in response to standing from a supine position in subjects with normal renal function. 2. We selected 43 healthy males in the second through to the seventh decade of life and gave them a constant dietary sodium intake before the study period. Renal function was estimated by standard clearance methods with the subject in a state of euvolaemia. 3. The mean daily urinary excretion of sodium was 236 +/- 22 mEq. Standing from a supine position was associated with significant decreases (P < 0.0001) in creatinine clearance (from 125 +/- 18 to 117 +/- 19 mL/min per 1.73 m2), sodium excretion (from 178 +/- 29 to 97 +/- 23 microEq/min) and fractional excretion of sodium (from 1.02 +/- 0.19 to 0.60 +/- 0.13%). A significant increase (P < 0.0001) in the RVR index (from 0.11 +/- 0.03 to 0.14 +/- 0.04 units) was noted. Univariate analysis indicated that while the change in RVR associated with standing was significantly diminished (P < 0.05) in older subjects, orthostatic changes in other parameters associated with standing were minimally influenced by age. 4. In conclusion, although the renal vascular response is impaired in advanced age, the renal functional response to orthostasis is otherwise maintained in healthy elderly subjects under conditions of normal sodium intake and clinical euvolaemia.

Second morning urine method is superior to the casual urine method for estimating daily salt intake in patients with hypertension

“…32 A second possible explanation is the effect of posture, as the difference between a recumbent posture and standing is about twofold sodium excretion. 33 This is equivalent to 1.3 (¼2 0.392 ) times the salt intake estimated by CU method, suggesting that posture has a considerable impact on the estimated intake. As there were no restrictions on posture except from 0600 to 0800 hours, changes of posture may have been responsible for the different percent increases among the three different salt intake groups.…”

Effectiveness of a Spot Urine Method in Evaluating Daily Salt Intake in Hypertensive Patients Taking Oral Antihypertensive Drugs

“…Values obtained by the SUM correlated highly with those from determinations of 24-h urinary sodium excretion (r= 0.73). The usefulness of the SUM has been confirmed in population studies (8)(9)(10)(11) and in hypertensive patients who were taking no medicine (12,13). While calcium channel blockers (14), angiotensin-converting enzyme inhibitors, and diuretics (15) have a natriuretic action, α-blockers (16) have an anti-natriuretic action, and these differing effects presumably could affect daily salt intake estimated by SUM in med-icated patients by altering the circadian rhythm of sodium secretion (17).…”

Urinary Sodium and Potassium Excretion and Risk of Cardiovascular Events

“…18 Previous studies have reported that this approach provides a valid estimate of sodium intake in healthy control participants 18 and patients taking antihypertensive therapy, 19 and has been used in previous studies. [20][21][22] Additional Assessment of Validity and Reliability of Urinary Sodium…”