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Dynamic changes in sodium handling in the distal nephron during sympathetic stimulation in healthy males
Author(s) -
Petersen Johan Casper Grove,
HolsteinRathlou NielsHenrik,
Sørensen Charlotte Mehlin,
Petersen Lonnie Grove,
Jonassen Thomas
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.621.6
Subject(s) - hypovolemia , medicine , heart rate , baroreceptor , blood pressure , baroreflex , cardiac output , endocrinology , anesthesia , stroke volume , excretion
Aim Hypovolemia, functional or by blood loss, is associated with decreased venous return and stroke volume. Baroreceptor mediated sympathetic reflexes are activated to increase heart rate to maintain cardiac output, while additional neuro‐humeral responses supress renal sodium excretion. By application of lower body negative pressure (LBNP) to induce graded central hypovolemia, we tested the hypothesis, that low‐pressure cardio‐pulmonary baroreceptors are the main efferent renal neural pathway to sodium retention in the distal part of the nephron. Methods We simulated mild and/or severe hypovolemia in twenty‐four healthy males (age 23 ± 3 yrs, height 182 ± 7 cm, weight 75 ± 9 kg; mean ± SD) by application of LBNP at 0 mmHg, −15 mmHg or −30 mmHg. All subjects followed a 3‐day regimen of supplemental sodium ingestion prior to the trial and ingested 600 mg Li + p.o. 10 hours prior to the trial. Urine samples were collected every 15 minutes during 1.5 hours of LBNP application and 1 hour of recovery. The ratio of excretion, C Na /C Li , was used as a measure for changes in sodium handling in the distal part of the nephron. Results LBNP of −15 mmHg and −30 mmHg caused a decrease in C Na /C Li of −3.53±0.69% (P<0.0001) and −2.79±0.49% (P<0.0001), respectively. There was no significant difference in the decrease in C Na /C Li between the two interventions. Heart rate was unchanged in the −15 mmHg group, but significantly elevated in the −30 mmHg group. Stroke volume and pulse pressure were both significantly lower in the −30 mmHg group. Conclusion We have shown, that the significant decrease in distal sodium clearance is similar during LBNP of both −15 and −30 mmHg even though the increased arterial baroreceptor unloading is pronouncedly increased during −30 mmHg. Our data support an efferent sympathetic neural pathway from the low‐pressure pulmonary baroreceptors in regulation of distal renal sodium excretion, which is suppressed even at mild central hypovolemia. Moderate volume depletion including activation of arterial baroreceptors did not cause further suppression of distal renal sodium excretion.