Trypanosoma lewisi: alterations in membrane function in the rat. |
| |
Authors: | W P Schraw G L Vaughan |
| |
Institution: | Department of Zoology, University of Tennessee, Knoxville, Tennessee 37916, U.S.A. |
| |
Abstract: | DEAE-cellulose-purified Trypanosoma lewisi from 4-day (dividing trypanosomes) and 7-day (non-dividing trypanosomes) infections in rats were compared for initial uptake of glucose, leucine, and potassium. Glucose entered the parasitic cells by mediated (saturable) processes, whereas leucine and K+ entered by mediated processes and diffusion. Glucose entry was significantly elevated in 4-day cells (Vmax 4.00 ± 1.02 nmoles/ 1 × 108 cells/min) with respect to 7-day cells (Vmax 1.83 ± 0.62 nmoles 1 × 108 cells/min). Likewise, the affinity of the glucose carrier was significantly greater in 4-day cells (Km = 0.30 ± 0.02 mM) than in 7-day cells (Km = 0.59 ± 0.11 mM). When leucine and K+ transport were compared in 4- and 7-day populations, significant elevations in the rate of entry (Vmax) of both substrates were observed for 4-day cells; Km values for leucine and K+ were not altered by the stage of infection. For leucine, the Vmax and Km for 4-day cells were 2.40 ± 0.50 nmoles/1 × 108 cells/30 sec and 78 ± 7 μM, respectively; corresponding values in 7-day cells were 1.06 ± 0.02 nmoles/1 × 108 cells/30 sec and 66 ± 11 μM. For K+, the Vmax and Km for 4-day cells were 15.97 ± 0.38 nmoles/1 × 108 cells/min and 1.2 mM, respectively; corresponding values in 7-day cells were 4.76 ± 1.82 nmoles/1 × 108 cells/min and 1.05 mM. The observed increase in the rate of K+ entry into 4-day cells was attributable to enhanced influx; no significant difference in the rate of K+ efflux was noted when 4- and 7-day cells were compared ( of K+ leak for 4- and 7-day cells were 68.1 ± 9.3 and 67.9 ± 15.2 min, respectively). Potassium influx was ouabain insensitive. Membrane function in 7-day cells was not uniformly inhibited. No significant difference in the activity of the membrane-bound enzyme, 5′-nucleotidase, was observed when 4- and 7-day cells were compared. |
| |
Keywords: | Hemoflagellate Protozoa parasitic Membranes Transport Rat Ablastin Metabolism DEAE-cellulose chromatography Glucose Leucine Potassium |
本文献已被 ScienceDirect 等数据库收录! |
|