Estimation of total body water (virtual tritium space) in the rat, cat, rabbit, guinea‐pig and man, and of the biological half‐life of tritium in man

Abstract

Isotopes of water (deuterium oxide and tritium oxide) have been used for the determination of total body water in certain mammalian species (Hevesy & Hofer, 1934;Pace, Kline, Schackman & Harfenist, 1947; Soberman, Brodie, Levy, Axelrod, Hollander & Steele, 1949;Haigh & Schnieden, 1956;Langham, Eversole, Hayes & Trujillo, 1956; Fallot, Aeberhardt & Masson, 1957). However, the techniques involved in these determinations have limited use, being either difficult, expensive or timeconsuming. Recent advances in scintillation counting techniques (Haigh, 1957) have made it much easier to estimate one of these isotopes of hydrogen, namely tritium. The purpose of the present paper is to describe how far such scintillation counter techniques can be applied to the determination of tritium in urine and plasma and the estimation of degree of error involved. The use of such techniques for a comparative study of total body water in a number of mammalian species and of water turnover under tropical conditions in one species, namely man, is also presented. METHODS 0-5 ml. of tritiated water or processed tritiated plasma or urine (see below) was added to 8 ml. of absolute ethanol and 10 ml. of scintillation solution (3 g 2:5-diphenyloxazole/l. sulphur-free toluene). The mixture was shaken and then centrifuged at approximately 1500 rev/min for 2-3 min. 5 ml. of the supernatant fluid was placed in the special counting container supplied with the N612 Ekco Scintillation Counter. This scintillation unit was kept at -20°C in a deep-freeze cabinet and its amplifier set at maximum gain. It was connected to a N 530E Ekco Automatic Scaler unit which was set at H.V. 1200 and Discrimator bias of -5 V. The scaler received a stabilized current from a constant-voltage stabilizer (Servomex AC 2 Mark IIB). Unless otherwise stated, all specimens were counted for 1000 sec and were allowed to cool in their counting containers for 1000 sec at -20°C before counting.Preparation of urine. 3*5 ml. of urine was mixed thoroughly in a test-tube with 0 5 g of activated charcoal. The resultant sludge was filtered through a Whatman No. 2 filter paper and 0 5 ml. of the filtrate was then added to 18 ml. of the alcohol-scintillator mixture, shaken and centrifuged, and a 5 ml. portion taken for counting. J. M. FOY AND H. SCHNIEDENPreparation of rat, cat, guinea-pig or rabbit plasma. 0*5 ml. of plasma was added to 18 ml. of the alcohol-scintillator solution mixture. After thorough shaking the mixture was centrifuged. 5 ml. of the clear supernatant fluid was then withdrawn and placed in the counting container before counting.Preparation of human plasma. Since it was found that the above method of preparation for rat plasma gave a coloured (orange-yellow) supernatant liquid with human and baboon plasma, another method was also investigated. The plasma was precipitated with 10 % trichloroacetic acid (Langham et al. 1956) and 0 5 ml. of the clear colourless filtrate was mixed with 18 ml. of alcohol-scintillation fluid mixture. 5 ml. of this final mixture was used f...

Pharmacokinetics, Bioavailability, Tissue Distribution, Excretion, and Metabolite Identification of Methoxyflavones in Kaempferia parviflora Extract in Rats

“…The calculated V d values of methoxyflavones were 8.79, 7.95, and 9.85 l/kg for PMF, TMF, and DMF, respectively. The body water of rat is 57 to 72% body weight (Foy and Schnieden, 1960). Therefore, the methoxyflavones may mostly distribute in body water.…”

Use of glacial and terrestrial habitats by harbor seals in Glacier Bay, Alaska: costs and benefits

“…Pregnancy was determined by presence of a solid lump in an enlarged abdomen and, in some individuals, presence of a vaginal mucus plug. Following sedation, non-pregnant seals received an intramuscular injection of 0.4 to 0.6 g kg -1 deuterium oxide to estimate percent body fat based on total body water by hydrogen isotope dilution (Foy & Schnieden 1960). A post-deuterium blood sample was collected 2.5 h later, after deuteri um equilibrium had occurred.…”

Maximal Rates of Excretion and Synthesis of Urea in Normal and Cirrhotic Subjects

“…If they now ingest (at 0 h) 0.27 (dose A), 0.40 (dose B), 0.53 (dose C), 0.94 (dose D), or 1.33 (dose E) g protein N/kg BW3' (in the form of casein, ovalbumin, or lactalbumin), the rate of urea N excretion accelerates within 4 h. At dose C a maximal rate of urinary urea N excretion (MRUE) is reached, which averages 55 mg urea N/h per kg BW3' and which persists for 16 h. Higher doses of protein do not further accelerate urea excretion, but prolong the duration of MRUE to 28 h (after dose E). Blood urea N (BUN) rises by [7][8][9][10][11][12][13][14][15][16][17][18][19][20] mg/100 ml during the first 8 h after dose C to E, and remains stable within ±5 mg/100 ml during the ensuing 8-28 h of MRUE. Each increment of protein above dose C causes a further increment in plasma a-amino N. During infusion of free amino acids at a rate of 110 or 165 mg amino acid N/h per kg BW3' for 12 h, rate of urea excretion increases to the MRUE value produced by dose C-E of oral protein.…”

“…Oral neomycin reduces the proportion of urea hydrolyzed in the gut to less than 20%; its extent is measured by recovery in the urine of a tracer dose of ["4C]urea injected intramuscularly during determination of MRUE. Accumulation of urea in body water is estimated from increment in BUN during the period of MRUE measurement (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24) h after dose E of casein) and from body water INTRODUCTION Hepatic enzymes incorporate NH3 and the amino groups of amino acids into urea, the principal end-product of N metabolism. In normal subjects, the rate of urea production is known to be proportional to protein intake, but the maximal rate which can be achieved has not been measured.…”