Experience With the Chromic Oxide Method of Fecal Marking in Metabolic Balance Investigations on Humans

Abstract

In metabolic balance studies the assessment of the subject's state of balance is derived from estimates of the dietary intake and the excretion in the urine and feces of the constituent under investigation. It Many investigators employ the "time-marker" method for obtaining quantitative fecal collections giving, for instance, two doses of carmine as a marker, collecting the feces passed between the time of appearance in the feces of the first and second doses of marker, and relating this collection to the diet consumled and uirine passed in the interval between the giving of the markers. The success of this method depends upon the clear recognition of the marker in the feces and the accurate collection of all feces passed during the period of study. In investigations in which no marker is employed (i.e., simple "time-collection" studies), accuracy also depends upon the subject's having a regular pattern of colonic emptying.The "inert indicator" method provides an alternative means of estimating the fecal component in balance studies, and it has the big advantage of avoiding the dependence on quantitative fecal collections. It was first used in experiments with animals, and a summarized description of the "Edin indicator method," which used chromium sesquioxide (Cr9O3), was given by Edin, Kihlen and Nordfeldt (1). The theory of the method has been discussed by Stanley and Cheng (2). Various substances have been tried as indicators, but all have to fulfill the following criteria: they should neither be absorbed from nor be chemically altered in the digestive tract (and so be fully recoverable from the feces); they should be nontoxic and should not interefere with the processes of digestion; they should be uniformly dispersed in the feces, after a stufficient time for attainment in the bowel of a steady state with respect to the indicator; and they should be readily estimated quantitatively in feces.Several indicators have been used in a wide range of investigations on different species of animals (e.g., 3-5), but the principal indicators employed in human studies have been Cr.,O3 (1, 2, 6-8) and polyethylene glycol (9, 10). Animal experimiients had shown that Cr2O3 met all the required criteria, and this has been confirmed for man in the above accounts of its application and in our experience. These earlier accounts all had shown that its use in man provided a valid basis on which to express fecal analytical data, when compared wvith "time-collection" studies; one investigation (7) also showed that fecal analyses based on Cr,O3 compared satisfactorily with car-

The Effect of 25-Hydroxy Vitamin D3 in the Osteomalacia of Chronic Renal Failure

“…They were given a diet which was similar in content to that to which they were accustomed whilst at home. Capsules containing 33 mmol (0.5 g) of acid-washed chromium sesquioxide were given three times a day with meals as a continuous faecal marker (Whitby & Lang, 1960). Food, faeces and urine were analysed for calcium and phosphorus content.…”

The Effect of a High Intake of Calcium and Phosphate in Normal Subjects and Patients with Chronic Renal Failure

“…Chromium sesquioxide was used as a continuous faecal marker. Capsules containing 0·5 g of acid washed chromium sesquioxide were given three times a day with meals (Whitby & Lang, 1960). Carmine markers were used in all subjects at the beginning of the balance and to delineate the equilibrium period.…”

Estimation of Fat Absorption From Random Stool Specimens

“…Subsequent studies on humans showed that equally good intestinal mixing could be achieved if the indicator was given in capsules twice or thrice daily. 5,9 The total amount of indicator fed could be recovered from stools within 48-72 hours of the last dose.5·7"9…”

“…Analy¬ sis of stools for both indicator and test substances was made by chemical methods. 9 By using radioactive cholesterol, Stanley (1) It is not absorbed from the intestinal tract and does not have the potentially ir¬ ritant effect of chromium. Its degradation product is niobium which is also nonabsorbable and has a spectrum similar to Zr95.…”