Plasma clearance of [51Cr] albumin into the intestinal tract of normal and chronically diarrheal horses.

Five clinically normal, mature horses and 11 with chronic diarrhea were given 51Cr-tagged Cohn fraction V equine albumin intravenously. All urine and feces were collected separately, and blood for plasma analysis was taken periodically for 5 to 8 days after injection of the isotope. Plasma clearance of albumin into the intestinal tract of normal horses was calculated as 0.67 +/- 0.23 (SD) ml/kg of body weight/day, with 1.33 +/- 0.69% of the 51Cr dose appearing in the feces in 5 days. Of the 11 diarrheal horses, 8 had a plasma clearance of 0.49 +/- 0.21 ml/kg/day with 1.12 +/- 0.68% of the dose of 51Cr in a 5-day fecal collection, suggesting that excessive losses of plasma protein into the bowel was not a component of their intestinal disease. The 3 other diarrheal horses had a marked protein-losing enteropathy; 1 of these horses had granulomatous enteritis due to Mycobacterium avium infection; another had severe intercellular edema of small and large intestinal mucosa, cause unknown; and intestinal biopsies were not obtained from the 3rd horse. The results suggest that: (1) as with other species that have been studied, daily loss of plasma protein into the bowel of horses is small; (2) most horses with chronic diarrhea do not have protein-losing enteropathy.