Abstract
The present study examined the effect of chronic renal failure (RF) on biotin transport in rat intestine. Chronic RF was induced by subjecting rats to right nephrectomy and left two-thirds nephrectomy. Control rats underwent sham operation but without tissue removal and were pair fed. Transport studies were performed 5 to 6 weeks after operation. Chronic RF was found to cause a marked decrease in the maximal velocity (Vmax) of biotin mucosal-to-serosal transport in jejunal everted sacs with minimal change in the apparent Michaelis-Menten constant (Km) of the transport process. This impairment in biotin transport was found to involve the transport process of the vitamin across the brush border membrane (BBM) domain of the enterocyte as shown by studies with BBM vesicles (BBMVs). These studies with BBMV similarly showed a decrease in the Vmax of biotin transport with minimal change in the apparent Km. The impairment of biotin transport in intestinal BBMVs was not due to dissipation of the Na+ gradient across the BBM (which is the driving force of biotin movement across this membrane) because transport of sodium 22 was found to be similar in BBMVs prepared from the RF rats and the sham-operated PF control rats. These results demonstrate that chronic RF in rats causes impairment in biotin intestinal transport. This impairment is due to a decrease in the number (and/or activity) of the biotin transport carriers and involves the transport process of biotin at the BBM.