Polyamines in human and rat milk influence intestinal cell growth in vitro.
BACKGROUND
Polyamines are required for intestinal growth and development. In this study, we examined whether milk can supply the polyamines needed for growth of IEC-6 cells, a line on non-transformed rat intestinal crypt cells.


METHODS
Human, bovine, and rat milk, and cow's milk-based infant formula were studied. Human, bovine, and rat milk were defatted and sterilized by filtration. IEC-6 cells were stabilized in Dulbecco's modified Eagle's medium (DMEM) containing 0.5% fetal bovine serum, 5 mM L-glutamine, 100 U/mL penicillin and 100 microg/mL streptomycin for 24 h at 37 degrees C. Thereafter, to initiate active growth, cells were placed in fresh DMEM containing 5% FBS (plus the other ingredients) supplemented with 5% (vol/vol) milk or infant formula. In some experiments, cells were also treated with difluoromethylornithine (2.5 mM) (DFMO), an inhibitor of polyamine synthesis, or dialyzed milk plus DFMO. After 44 hours of culture, cells were pulsed with 3H-thymidine (3H-TdR) for 4 hours, harvested and the radioactivity incorporated into DNA was measured.


RESULTS
Human and rat milk stimulated proliferation of IEC-6 cells (p < 0.05 compared to controls); addition of DFMO did not reverse the stimulatory effect. Bovine milk and the infant formula did not stimulate proliferation or prevent the growth inhibition induced by DFMO. After dialysis, human milk had less ability to reverse the DFMO inhibition (p < 0.05).


CONCLUSIONS
These experiments suggest that both human and rat milk, but neither bovine milk nor the infant formula, contain sufficient bioactive polyamines to sustain cell growth during inhibition of polyamine synthesis.
Capano
G
G
Department of Pediatrics, Harvard Medical School, Massachusetts General Hospital, Boston, USA.
Bloch
K J
KJ
Carter
E A
EA
Dascoli
J A
JA
Schoenfeld
D
D
Harmatz
P R
PR
D000818:Animals; D002417:Cattle; D002455:Cell Division / Q000187:drug effects*; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D003956:Dialysis; D000518:Eflornithine / Q000494:pharmacology; D006801:Humans; D007225:Infant Food; D007422:Intestines / Q000166:cytology*; D008892:Milk / Q000737:chemistry*; D008895:Milk, Human / Q000737:chemistry*; D008970:Molecular Weight; D011073:Polyamines / Q000032:analysis / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D051381:Rats; D013095:Spermidine / Q000494:pharmacology; D014316:Tritium
D011073:Polyamines; D014316:Tritium; D004247:DNA; D013095:Spermidine; D000518:Eflornithine