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Extracellular space and diffusion barriers in muscle fibres from Megabalanus psittacus (Darwin).

1979; Wiley; Volume: 288; Issue: 1 Linguagem: Inglês

10.1113/jphysiol.1979.sp012696

1469-7793

Juan Bacigalupo, Mario Luxoro, S. Rissetti, Cecilia Vergara,

thermodynamics and calorimetric analyses

1. Muscle fibres from Megabalanus psittacus (Darwin) were used to measure the exchange of Na+ and Ca2+ between intracellular and extracellular compartments. 2. The size of the extracellular space was evaluated directly from electron micrographs at 6.1 +/‐ 0.5% (percentage of the fibre volume). The more conventional estimates using Na+ and 134Cs+ as space markers gave higher values, namely, 8.9 +/‐ 0.7 and 9.5 +/‐ 1.5%. 3. An average value of 9.2% was used to correct the total Na+ and K+ in the muscle fibres and to estimate the intracellular concentrations of Na+ and K+ as 39 +/‐ 4 and 202 +/‐ 11 mM respectively. 4. Na+ (and similar Ca2+) washout curves could be described using a three compartments diffusion model. The data analysed in terms of this model enabled us to estimate membrane permeabilities as PNa+ = 2.7 x 10(‐7) and PCa2+ = 2.7 x 10(‐7) cm/sec.