Renal and intestinal hexose transport in familial glucose-galactose malabsorption

Abstract

A B S T R A C T Glucose transport by jejunal mucosa in vitro and kidney in vivo was investigated in a 3 yr old patient with congenital glucose-galactose malabsorption, her family, and 16 normal volunteers. Glucose transport by normal human jejunal mucosa was concentrative, saturable, sodium and energy dependent, and exhibited competitive inhibition. Biopsy specimens from six nor- mal controls and an asymptomatic 5 yr old brother of the proband accumulated glucose to concentrations 16 times that in the incubation medium. The proband's mucosa was unable to concentrate glucose throughout a 60 min incubation period. Both of her parents and a half sister demonstrated impaired glucose transport. Their values fell between normal and those of the proband. Influx of glucose was impaired but efflux of glucose from the mucosa of these three heterozygotes was iden- tical with that in three normal controls. A kinetic analy- sis indicated a reduced capacity (Vmax), but a normal affinity (K.) for glucose transport by their intestinal mucosa. All subjects accumulated fructose similarly.