Wp. Goddard et al., IRON UPTAKE BY ISOLATED HUMAN ENTEROCYTE SUSPENSIONS IN-VITRO IS DEPENDENT ON BODY IRON STORES AND INHIBITED BY OTHER METAL-CATIONS, The Journal of nutrition, 127(1), 1997, pp. 177-183
The uptake of Fe-59 ascorbate by suspensions of human enterocytes prep
ared from endoscopically derived duodenal biopsies was studied, with e
ach subject's serum ferritin concentration determined at the time of e
ndoscopy. Iron uptake was greatest at 37 degrees C. Uptake increased f
rom pH 5.5 to 7.3, before being totally inhibited at pH 9.0. However,
ferrous ion concentration, determined by 3-(2-Pyridyl)-5,6-bis(4-pheny
l sulfonic acid)-1,2,4-triazine, was greatest at pH 5.5 and fell over
this pH range. The rate of uptake was significantly greater by enteroc
ytes isolated from individuals with a low serum ferritin (<22 ng/L) co
mpared with those with normal serum ferritin (>22 ng/L). V-max +/- (SE
M) was 78.7 +/- 8.5 pmol Fe/(mu g DNA . min) in the normal group (n =
12) and 141 +/- 17.2 pmol Fe/(mu g DNA . min) in the low ferritin grou
p (n = 4, P < 0.008). Corresponding K-m values were 52.5 +/- 11.7 and
66.7 +/- 5.1 mu mol/L, respectively (P < 0.91). Zinc, lead, cobalt and
manganese added to the incubation buffer significantly lowered iron u
ptake into cells (unselected patients). The concentrations of each met
al required to halve the uptake rate from 50 mu mol/L iron (IC50) were
85 +/- 5 mu mol/L (Zn), 570 +/- 170 mu mol/L (Pb), 1.1 +/- 0.1 mmol/L
(Co), and 3.8 +/- 0.7 mmol/L (Mn). The results demonstrate that enter
ocytes isolated by this method show the characteristics of iron uptake
seen in animal studies. We suggest that these cells will be useful in
the study of iron uptake in humans.