Alexander P. Remenchik

PROBLEMS INVOLVED IN ACCURATELY MEASURING THE K CONTENT OF THE HUMAN BODY.

An accurate measurement of the body potassium content of humans and animals has many applications, as is suggested by the various papers to be presented today. The development of highly sensitive “whole-body counters” about ten years ago apparently made it possible to measure accurately the total body potassium content of the living animal. During the last two years, several whole-body counters have been built specifically for this purpose. However, the extreme accuracy required to attain the objectives of some of these studies may be beyond the capability of these instruments. It is very difficult to assess the accuracy of the K measurements of humans with these counters because there is no direct method of measuring the potassium content of the living human. In animal measurements this presents no problem because the animal can be sacrificed and the K determined by chemical analysis as Kirtin’ has done. Thus, the accuracy of the results for humans can only be evaluated by analyzing the data for internal consistency or by comparing them to the results obtained by other indirect methods such as isotopic-dilution techniques2 This paper will discuss: (1) the basic problems of measuring the K content of the intact animal, ( 2 ) one of the measurement techniques which uses a NaI( T1) crystal as the detector, and ( 3 ) an analysis of the results that have been obtained with this counter. The results obtained with 4.rr liquid counters will be discussed by E. C. Anderson.

Depletion of Body Potassium by Diuretics

A study was designed to evaluate the [see table in the PDF file] [see table in the PDF file] hypothesis that the hypokalemia associated with the administration of thiazide diuretics reflects a redistribution of potassium rather than a depletion of body potassium. Exchangeable potassium, total body potassium, total body water, extracellular fluid volume, and serum sodium, potassium, chloride, bicarbonate, and pH of a group of hypertensive subjects were measured before and after 4 weeks of administration of dichlorphenamide and hydrochlorothiazide to these subjects. Significant decreases were observed in serum potassium (1.05 mEq/L), serum chloride (8.22 mEq/L), exchangeable potassium (21.1%), and total body potassium (16.7%) without a significant change in serum pH, sodium, and bicarbonate. Body weight, total body water, and extracellular fluid volume also decreased, but the change in body weight was not sufficient to explain the potassium deficit produced. The mechanisms responsible for the loss of potass...

Effects of Diuretic Agents on Serum and Tissue Electrolytes in Rats.

Summary and Conclusions Hydrochloro thiazide, polythiazide and chlorthalidone were added to the diets of 3 groups of Sprague-Dawley rats. After 4 weeks of subsistence on this diet, these animals together with matched controls were sacrificed and analyses of serum and tissue electrolytes were done. The serum chloride concentration was significantly lower in each experimental group. Serum potassium concentration was decreased in all 3 groups, and was significantly lowered in the groups receiving chlorthalidone and hydrochlorthiazide. Changes in serum sodium concentration were not statistically significant. Tissue analyses revealed no significant alterations in water or electrolyte content. These studies suggest that the hypokalemia associated with oral diuretic therapy results from a redistribution of potassium stores rather than a frank depletion of this ion in rats.

Determination of Body Composition by Gamma Spectrometry

The use of whole-body counters to assess the potassium content in the human body is discussed. The paper reviews the basic problems of measuring potassium content of the intact organism, one of the measurement techniques which uses a NaI(Tl) crystal as a detector, and an analysis of the results that were obtained with this counter.