Putrescine uptake and release by a normal rat small intestine crypt cell line, IEC-6.
IEC-6 cells were cultured on permeable filter inserts with separate access to the apical and basolateral sides. [3H]Putrescine uptake favored the apical side and its release (in Earle's balanced salt solution containing 0.1% bovine serum albumin) was six times greater in the apical-to-basolateral than in the basolateral-to-apical direction. Release in DMEM did not show this preference. The uptake of [3H]putrescine was stimulated approximately 1.3 times the basal level by 10 mM asparagine (ASN) or 5% dialyzed fetal bovine serum whether the [3H]putrescine was added at a concentration of 1 or 100 nM. The increased uptake was maintained for up to 6 h. When [3H]putrescine was removed after 4 h of uptake, the cells continued to release it into the medium on both sides for up to 4 h. Stimulated cells released only 50% as much as unstimulated cells. Unlabeled putrescine reduced the uptake of [3H]putrescine with an IC50 of 1.81 x 10(-6) M (r = 0.9476) and 1.02 x 10(-6) M (r = 0.9967) for unstimulated and ASN-stimulated cells, respectively. When the intracellular putrescine was reduced by difluoromethylornithine, the uptake of [3H]-putrescine was not changed, but its release was inhibited. Sodium was not required for [3H]putrescine uptake or release. Although the stimulated cells attained intracellular levels of [3H]putrescine which, if expressed as concentration based on cell volume, were up to 500 times the original extracellular concentration, a true concentration gradient could not be proven because 85% of the [3H]putrescine was probably bound to polyanions as shown by butanol extraction.
McCormack
S A
SA
Department of Physiology and Biophysics, University of Tennessee, Memphis 38163.
Johnson
L R
LR
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D000440:Butanols / Q000737:chemistry; D002451:Cell Compartmentation; D003902:Detergents; D004072:Digitonin / Q000737:chemistry; D000518:Eflornithine / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism; D005990:Glycerol / Q000737:chemistry; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology; D011092:Polyethylene Glycols / Q000737:chemistry; D011700:Putrescine / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D012995:Solubility
D000440:Butanols; D003902:Detergents; D011092:Polyethylene Glycols; D004072:Digitonin; D005990:Glycerol; D011700:Putrescine; D000518:Eflornithine