Transport of monovalent thallium across the membrane of oocyte of the lamprey Lampetra fluviatilis

Autor: A. A. Lapin, A. O. Sherstobitov, V. V. Glazunov, A. A. Nikiforov
Rok vydání: 2010
Předmět:
Zdroj: Journal of Evolutionary Biochemistry and Physiology. 46:235-240
ISSN: 1608-3202
0022-0930
DOI: 10.1134/s0022093010030026
Popis: Mechanisms of transport of monovalent thallium across the membrane of oocyte of the lamprey Lampetra fluviatilis were studied by using 204Tl. The Tl+ transport in lamprey oocytes has been shown to be realized by at least two pathways: through Na/K-pump and by mechanisms of Na,K,Cl-cotransport. In the standard Ringer solution (mM): 4 KCl, 140 NaCl, 0.5 CaCl2, 5 glucose, 10 Tris-HCl-in the presence of ouabain, the coefficient of the 204Tl stationary distribution (cell/medium) was within the range of 2.3–2.5, while the time necessary to reach its 50% value amounted to 40–45 min at 20°C. In potassium-free media, transport of 204Tl via Na/K-pump was described by simple kinetics with saturation and was characterized by the value V max = 520 pmol/(cell h) and K M = 0.3 mM. In the presence of 4 mM K+ and 0.1 mM/1 Tl+, the ouabain-sensitive Tl+ flux decreased to 75 pmol/(cell h). At activation of the mechanism of Na,K,Cl-cotransport by the outer Na+ (in Na-NMDG media of different composition) the total influx of Tl+ reached 193 ± 20 pmol/(cell h), while the bumetanide-sensitive component—119 ± 12 pmol/(cell h) with K M for Na+ about 20 mM. In the incubation media with variable concentration of chloride ions (replacement of Cl− by NO3) the total Tl+ flux reached 220 ± 21, while via the mechanisms of Na,K,Cl-cotransport—87 ± 8 pmol/(cell h). Under our experimental conditions, mechanisms of active transport and Na,K,Cl-cotransport accounted for 94% of the Tl+ influx. The potassium channels that usually are permeable also to monovalent thallium ions were not revealed.
Databáze: OpenAIRE
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