Effects of concanavalin A and phorbol myristate acetate on glutamine metabolism and proliferation of porcine intestinal intraepithelial lymphocytes
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This study was designed to determine the effects of concanavalin A (ConA) (a T-cell mitogen) and phorbol myristate acetate (PMA) (an activator of protein kinase C) plus ionomycin (Iono) on glutamine metabolism and proliferation of porcine intestinal intraepithelial lymphocytes (IEL). IEL were prepared from jejunum of 29-day-old pigs weaned at 21 days of age. Cells were cultured at 37 degrees C for 48 hr in RPMI-1640 medium containing 10 mM D-glucose, 0 to 4 mM L-glutamine, 0 to 5 micrograms/ml ConA, or 20 ng/ml PMA + 375 ng/ml Iono. The medium was also supplemented with 0 or 0.1 mM adenosine, guanosine, inosine, uridine or cytosine to study the effect of nucleosides or bases on IEL proliferation. IEL proliferation was assessed by pulsing with 3H-thymidine for 18 hr. Glutamine metabolism was studied in incubated IEL in the presence of Krebs-Henseleit bicarbonate buffer containing 5 mM D-glucose and 1 mM L-[U-14C]glutamine. PMA+Iono markedly stimulated 3H-thymidine incorporation and glutamine metabolism to ammonia, glutamate, aspartate and CO2. When stimulated by PMA+Iono, rates of 3H-thymidine incorporation and glutamine metabolism were much lower in IEL than in mesenteric lymph node lymphocytes. Glutamine was required for IEL proliferation, and it could not be replaced by adenosine, guanosine, inosine, uridine or cytosine, suggesting that porcine IEL cannot interconvert purine and pyrimidine nucleotides. Porcine IEL poorly or not at all responded to ConA stimulation, in contrast to lymph node lymphocytes, in terms of both [3H]thymidine uptake and glutamine metabolism.
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