Abstract
Beckwith and Chanutin 1 state that “in the hypertensive partially nephrectomized rat, the plasma volume was increased, the red cell volume decreased and the total blood volume remained unchanged.” In referring to a paper by Griffith and Ingle, 2 who found an elevated blood volume in hypertensive partially nephrectomized rats, they say, “On inspection of their procedure for estimating blood volume, it appears that they neglected to take the red cell volume into consideration and the values reported by them probably represent plasma volumes… the increased plasma volumes (found by Beckwith and Chanutin) … agree with the reinterpreted data of Griffith and Ingle.”
The blood volume method used by Griffith and Ingle was that previously reported by Griffith and Campbell. 3 In this method 0.3 cc of 5% vital red is injected intravenously and 4 1/2 minutes later 50 cmm of whole blood are removed and placed in 2.95 cc of physiologic saline, the resulting volume being 3 cc and the blood dilution 1:60. After centrifuging, 2 cc of the supernatant fluid are removed and compared in a colorimeter with suitable standards. The red cells remain in the 1.0 cc left in the test tube, and a slight error is thus introduced in that the volume which the cells occupy is included in the 3 cc but does not contain an aliquot portion of the dye. The dye is actually contained in 3 cc less the volume of the cells. If the cells comprised 50% of the total blood, the figure would be 3.0 cc less .025 cc or 2.975 cc. This represents an error of 0.8%, and would make the calculated figure too low by that amount.
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