Lactate efflux from sarcolemmal vesicles isolated from rainbow trout Oncorhynchus mykiss white muscle is via simple diffusion
Rainie L. Sharpe* and
C. Louise Milligan
Department of Biology, The University of Western Ontario, London,
Ontario, Canada N6A 5B7
* Present address: Department of Biology, University of New Brunswick (Saint
John), PO Box 5050, Tucker Park Road, Saint John, New Brunswick, Canada, E2L
4M5

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Fig. 1. Lactate loss (pmol mg-1 protein) from rainbow trout white muscle
sarcolemmal vesicles over time. Vesicles were loaded with 25 mmol
l-1 lactate in 140 mmol l-1 KCl/Mops + 18.5 kBq
14C-lactate. Values are means ± 1 S.E.M.; N=6 (10,
15, 20, 40, 50 and 70 s values); N=10 (30, 60 s values); N=5
(100, 300 s values).
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Fig. 2. The effect of internal lactate concentration on lactate efflux from trout
white muscle sarcolemmal vesicles. All efflux was measured over a period of 1
min. N=7 (50 and 100 mmol l-1 lactate concentrations);
N=6 for 10 mmol l-1 lactate); N=4 (300 mmol
l-1 lactate); N=12 (25 mmol l-1 lactate).
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Fig. 3. (A) The effects of various inhibitors on lactate efflux from trout white
muscle sarcolemmal vesicles. All vesicles were loaded with 25 mmol
l-1 lactate and 18.5 kBq 14C-lactate. Values are means
± 1 S.E.M. Control (N=5): efflux was measured in KCl/Mops
buffer; STOP (N=10), efflux in ice-cold, 2.5 mmol l-1
HgCl2; 75 mmol l-1 Na (N=7): efflux in 75 mmol
l-1 KCl, 75 mmol l-1 NaCl Mops buffer; 5 mmol
l-1 CIN (N=6): efflux in KCl/Mops containing 5 mmol
l-1 -cyano-4-hydroxycinnamate; 5 mmol l-1 SITS
(N=11): efflux in KCl/Mops containing 5 mmol l-1
4-acetoamido-4'-isothyiocyanstilbene-2,2'-disulphonic acid.
*A significant difference (P<0.05) from the control
value. (B) The influence of pH gradient on lactate efflux from trout white
muscle sarcolemmal vesicles. Values are means ± 1 S.E.M.
pHi<pHe, N=11;
pHi>pHe, N=7,
pHi=pHe=5.1, N=5;
pHi=pHe=7.4, N=6. *A significant
difference (P<0.05) from the pHi=pHe=7.4
value.
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© The Company of Biologists Ltd 2003