title: Endogenous and exogenous female sex hormones and renal electrolyte handling: effects of an acute sodium load on plasma volume at rest.
abstract: This study was conducted to investigate effects of an acute sodium load on resting plasma volume (PV) and renal mechanisms across the menstrual cycle of endurance-trained women with natural (NAT) or oral contraceptive pill (OCP) controlled cycles. Twelve women were assigned to one of two groups, according to their usage status: 1) OCP [n = 6, 29 yr (SD 6), 59.4 kg (SD 3.2)], or 2) NAT [n = 6, 24 yr (SD 5), 61.3 kg (SD 3.6)]. The sodium load was administered as a concentrated sodium chloride/citrate beverage (164 mmol Na(+)/l, 253 mosmol/kgH(2)O, 10 ml/kg body mass) during the last high-hormone week of the OCP cycle (OCP(high)) or late luteal phase of the NAT cycle (NAT(high)) and during the low-hormone sugar pill week of OCP (OCP(low)) or early follicular phase of the NAT cycle (NAT(low)). The beverage ( approximately 628 ml) was ingested in seven portions across 60 min. Over the next 4 h, PV expanded more in the low-hormone phase for both groups (time-averaged change): OCP(low) 6.1% (SD 1.1) and NAT(low) 5.4% (SD 1.2) vs. OCP(high) 3.9% (SD 0.9) and NAT(high) 3.5% (SD 0.8) (P = 0.02). The arginine vasopressin increased less in the low-hormone phase [1.63 (SD 0.2) and 1.30 pg/ml (SD 0.2) vs. 1.82 (SD 0.3) and 1.57 pg/ml (SD 0.5), P = 0.0001], as did plasma aldosterone concentration ( approximately 64% lower, P = 0.0001). Thus PV increased more and renal hormone sensitivity was decreased in the low-hormone menstrual phase following sodium/fluid ingestion, irrespective of OCP usage.
authors.affiliation: School of Physical Education, University of Otago, Dunedin, New Zealand. stsims@stanford.edu
authors.forename: Stacy T
authors.initials: ST
authors.lastname: Sims
authors.forename: Nancy J
authors.initials: NJ
authors.lastname: Rehrer
authors.forename: Melanie L
authors.initials: ML
authors.lastname: Bell
authors.forename: James D
authors.initials: JD
authors.lastname: Cotter
mesh_terms: D000328:Adult; D001127:Arginine Vasopressin / Q000378:metabolism; D001642:Bicycling / Q000502:physiology; D001834:Body Water / Q000378:metabolism; D003278:Contraceptives, Oral, Hormonal / Q000494:pharmacology; D004573:Electrolytes / Q000378:metabolism*; D004997:Ethinyl Estradiol / Q000494:pharmacology; D005260:Female; D005498:Follicular Phase / Q000502:physiology; D012739:Gonadal Steroid Hormones / Q000494:pharmacology*; D006728:Hormones / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D016912:Levonorgestrel / Q000494:pharmacology; D008183:Luteal Phase / Q000502:physiology; D015233:Models, Statistical; D009997:Osmotic Pressure; D010953:Plasma Volume / Q000187:drug effects*; D011372:Progestins / Q000494:pharmacology; D012146:Rest / Q000502:physiology*; D012964:Sodium / Q000494:pharmacology*
chemical_list: D003278:Contraceptives, Oral, Hormonal; D004573:Electrolytes; D012739:Gonadal Steroid Hormones; D006728:Hormones; D011372:Progestins; D001127:Arginine Vasopressin; D004997:Ethinyl Estradiol; D016912:Levonorgestrel; D012964:Sodium