Induction of ornithine decarboxylase activity in mouse B lymphocytes.
We have examined the role in B cell activation of ornithine decarboxylase (ODC), the labile rate-limiting enzyme in the synthesis of polyamines thought to be required for S phase entry in all cells. When small resting mouse splenic B cells were stimulated with the mitogenic agents phorbol myristate acetate (PMA) plus ionomycin (lo), LPS or the B cell specific agent F(ab')2 anti-lg, ODC activity was greatly increased. ODC activity in small dense B cells remained near baseline levels for the first 6 h after treatment with LPS, but then increased approximately 150-fold in the next 18 h. When purified B cells were not separated by cell density, ODC activity was 30-fold greater at baseline and rose earlier after LPS stimulation, reaching a level about three times that of LPS-stimulated small, dense B cells at 24 h, implying that large (preactivated) B cells have much greater ODC responses than small, dense B cells. ODC activity, like S phase entry, could also be induced in small, dense B cells by PMA and lo but failed to respond to either agent alone. ODC levels rose transiently by approximately 40-fold between 2 and 6 h following stimulation of small B cells with F(ab')2 anti-lg, then declined to baseline. Whole anti-lg did not stimulate ODC activity and also blocked the F(ab')2 anti-lg mediated increase in ODC activity, just as it produced the expected inhibition of thymidine incorporation and cellular progression into S phase.(ABSTRACT TRUNCATED AT 250 WORDS)
Molitor
J
J
University of Iowa College of Medicine, Department of Internal Medicine and Microbiology, Iowa City 52242-1009.
Pace
W
W
Stunz
L
L
Vigna
J
J
Louie
S
S
Ashman
R
R
D000818:Animals; D001402:B-Lymphocytes / Q000201:enzymology*; D002453:Cell Cycle / Q000502:physiology; D002478:Cells, Cultured; D004790:Enzyme Induction; D005260:Female; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D015847:Interleukin-4 / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008213:Lymphocyte Activation / Q000502:physiology; D051379:Mice; D008815:Mice, Inbred Strains; D009955:Ornithine Decarboxylase / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000096:biosynthesis; D013154:Spleen / Q000166:cytology
D007140:Immunoglobulin Fab Fragments; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D015847:Interleukin-4; D009955:Ornithine Decarboxylase