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This Article Full Text Full Text (PDF) All Versions of this Article: 559/1/327    most recent jphysiol.2004.063289v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Patterson, M. J. Articles by Taylor, N. A. S. Search for Related Content PubMed PubMed Citation Articles by Patterson, M. J. Articles by Taylor, N. A. S.

Department of Biomedical Science, University of Wollongong, Wollongong, NSW 2522 Australia

We measured intra- and extravascular body-fluid compartments in 12 resting males before (day 1; control), during (day 8) and after (day 22) a 3-week, exercise–heat acclimation protocol to investigate plasma volume (PV) changes. Our specific focus was upon the selective nature of the acclimation-induced PV expansion, and the possibility that this expansion could be sustained during prolonged acclimation. Acclimation was induced by cycling in the heat, and involved 16 treatment days (controlled hyperthermia (90 min); core temperature = 38.5°C) and three experimental exposures (40 min rest, 96.9 min (S.D. 9.5 min) cycling), each preceded by a rest day. The environmental conditions were a temperature of 39.8°C (S.D. 0.5°C) and relative humidity of 59.2% (S.D. 0.8%). On days 8 and 22, PV was expanded and maintained relative to control values (day 1: 44.0 ± 1.8; day 8: 48.8 ± 1.7; day 22: 48.8 ± 2.0 ml kg^–1; P < 0.05). The extracellular fluid compartment (ECF) was equivalently expanded from control values on days 8 (279.6 ± 14.2versus 318.6 ± 14.3 ml kg^–1; n= 8; P < 0.05) and 22 (287.5 ± 10.6 versus 308.4 ± 14.8 ml kg^–1; n= 12; P < 0.05). Plasma electrolyte, total protein and albumin concentrations were unaltered following heat acclimation (P > 0.05), although the total plasma content of these constituents was elevated (P < 0.05). The PV and interstitial fluid (ISF) compartments exhibited similar relative expansions on days 8 (15.0 ± 2.2%versus 14.7 ± 4.1%; P > 0.05) and 22 (14.4 ± 3.6%versus 6.4 ± 2.2%; P= 0.10). It is concluded that the acclimation-induced PV expansion can be maintained following prolonged heat acclimation. In addition, this PV expansion was not selective, but represented a ubiquitous expansion of the extracellular compartment.

(Received 23 February 2004; accepted after revision 17 June 2004; first published online 24 June 2004)
Corresponding author M. J. Patterson: Chemical, Biological, Radiological and Nuclear Defence Centre, Defence Science and Technology Organization, PO Box 4331, Melbourne, Victoria, Australia 3001. Email: mark.patterson{at}dsto.defence.gov.au