Effects of an acute saline infusion on fluid and electrolyte metabolism in humans

Abstract

Several hormonal systems participating in body fluid and electrolyte homeostasis were investigated in six healthy volunteers in a supine body position during a period of 9 days and nights. Under strictly controlled conditions, striking circadian rhythms were observed for plasma levels of vasopressin, renin, aldosterone, guanosine 3',5'-cyclic monophosphate, cortisol, and epinephrine. Nocturnal decreases and diurnal increases in urine flow rate and urinary excretion of electrolytes were observed and closely paralleled the urinary excretion of urodilatin. During 48 h after an acute isotonic saline infusion (2 liters within 25 min) and after a 48-h control experiment the urinary excretion of H2O and electrolytes, and simultaneously the alterations in endocrine systems participating in body fluid homeostasis, were determined. Urine flow and urinary electrolyte excretion rates were significantly increased during 2 days after the saline infusion. The largest increase in urinary fluid and electrolyte excretion was observed between 3 and 22 h postinfusion. These long-term changes were paralleled by altered H2O and Na balances and also by elevated body weights that returned to baseline values with an approximate half-life of 7 h. These data suggest that vasopressin, atrial natriuretic peptide, and catecholamines are unlikely to be of major importance for the renal response to this hypervolemic stimulus. The renin-aldosterone system was suppressed during 2 days postinfusion. This suppression correlated with the effects of saline load on Na excretion. However, the closest relation with Na excretion was observed for the kidney-derived member of the atrial natriuretic peptide family, urodilatin, which was considerably increased during the long-term period up to 22 h postinfusion. Thus these data show that the human body in supine position requires approximately 2 days to regulate the amount of Na and H2O provided by an acute saline infusion. The data also suggest that urodilatin and the renin-aldosterone system might participate in the long-term renal response to an acute saline infusion and also in the mediation of circadian urinary excretion rhythms.

Radiocontrast‐induced natriuresis associated with increased urinary urodilatin excretion

“…Thus the present results are consistent with the hypothesis that urodilatin is a more likely mediator of the radiocontrast-induced natriuresis in this situation than atrial natriuretic peptide. This is in agreement with other investigations which indicate that urodilatin may be a particularly powerful paracrine regulator of renal sodium excretion [8,16,17].…”

Cardiovascular responses to lower body negative pressure before and after 4 h of head-down bed rest and seated control in men and women

“…Similarly, we did not observe changes in renin after sitting, but different findings have been reported concerning possible circadian effects. Previous investigations that maintained a supine posture throughout the day found that renin was lower in the afternoon (10,22), but a previous study in which seated posture was maintained also found no change in plasma renin activity (21). Plasma angiotensin II was significantly different after SEAT between the sexes; women increased and men decreased angiotensin II.…”

“…There were no changes in vasopressin levels after SEAT even though the men had, consistent with a previous investigation of sitting (21), a slight reduction in serum osmolality which might be expected to cause lower vasopressin (3). Perhaps a longer period of sitting or inactivity might have affected vasopressin as another study found reduced concentration in the afternoon in men in supine posture (10).…”

Absorption of irrigation fluid during XPS™ GreenLight laser vaporization of the prostate: results from a prospective breath ethanol monitoring study

“…This threshold volume has previously been identified to be of clinical relevance for isotonic saline influx [17]. Volume and chloride overload can lead to pulmonary edema, hyperventilation, hyperchloremic acidosis, reduced glomerular filtration rate (up to 15%), suppression of the renin-angiotensin system (up to 60%), hypotension, impaired myocardial function and abdominal pain [16][17][18][26][27][28]. The symptoms we observed were transient, only mild to moderate and did not require extensive treatment.…”