Other Urinary Sugars

Lactose is sometimes detected in the urine of women during lactation and occasionally toward the end of pregnancy. Patients with lactase deficiency, a common disorder caused by a congenital or acquired deficiency of intestinal lactase, exhibit abdominal pain, diarrhea, and lactose in the urine. 

Maltose has rarely been detected in the urine of some patients. 

Many reducing substances other than sugars may be found in urine (Box 25-6). Ascorbic acid (vitamin C) may be ingested in large quantities or may be present in antibiotic preparations administered intravenously. In either case, excess concentrations usually appear in the urine and contribute significantly to the total reducing substances present. 

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Qualitative Tests for Urinary Sugars Other Than Glucose Fructose (Selivanoff s Test)... 

An aqueous solution of a solid heavier than water has a higher-sp. gr. than pure water, the variation in sp. gr. following a. regular but different rate with each solid. In a simple solution— one of common salt in water, for instance—the lu-oportion of solid in solution can be determined from the sp. gr. In complex solutions, such as the urine, the sp. gr. does not indicate the proportion of solid in solution with accuracy. In the absence of sugar and albumen, a determination of the sp. gr. of urine affords an indication of the amount of solids sufficiently accurate for usual clinical purposes. Moreover, as urea is much in excess over other urinary solids, the oscillations in the sp. gr. of the urine, if the quantity passed in twenty-four hours be considered, and in the absence of albumen and sugar, indicate the variations in the elimination of urea, and consequently the activity of disassimilation of nitrogenous material. 

Another indication of the relevance of the Maillard reaction to human nutrition and metabolism was the finding of urinary loss of bound amino acids after infusion of autoclaved sugar (glucose or finctose)—amino acid or peptide solutions. Nonutilizable amino acids were detected in the blood and urine (S38, S39). After these and other reports, parenteral solutions were sterilized by nonheat methods. 

The test thus serves to distinguish pentoses and lactose from all other common reducing sugars. It is frequently applied to urine to distinguish glucose from (1) lactose, (2) urinary pentose, and (3) glycuronic acid, all of which reduce alkaline copper solutions. 

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