When we measure extracellular fluid volume, is transcellular fluid volume also measured?
When we measure extracellular fluid volume, is transcellular fluid volume also measured? How is the total volume of transcellular fluid determined?
Dineash Kumar, Year 1 Medical Student, School of Medicine, Asian Institute of Medicine, Science & Technology, 08100 Bedong, Kedah, Malaysia; e-mail: dineashkumar at yahoo dot com
Medical Physiology Online 
Reply to Dineash Kumar: When ECF volume is measured, is transcellular fluid volume also measured?
To quote C.J.Lote [1], “markers used to measure extracellular fluid volume do not penetrate into transcellular fluids, or do so extremely slowly. Consequently, transcellular fluid volume is not measured when ECF volume is measured”.
In a study [2] in which sodium selenate containing a radioactive isotope of selenium was used as a marker for measuring ECF volume, the marker was detected in cerebrospinal fluid and vitreous of the eye between 3-12 hr after infusion but later disappeared.
Thus, a single tracer is not available to measure the total volume of all transcellular fluids. Transcellular fluid volume is thus measured only when total body water is estimated.
Conflict of interests: none
References:
[1] Lote CJ. Principles of Renal Physiology, Springer, 2000.
[2] Albert SN, Albert CA, Hirsch EF et al. Selenate as a substitute for sulfate in the measurement of extracellular fluid volume. Journal of Nuclear Medicine 1966; 7: 290-303 [Free full text]
E.S.Prakash, Editor, Medical Physiology Online
May 8, 2009 at 2:37 AM