Abstract:Anion conductance and permeability sequences were obtained for frog skeletal muscle membranes from the changes in characteristic resistance and transmembrane potential after the replacement of one anion by another in the bathing solution. Permeability and conductance sequences are the same. The conductance sequence at pH = 7.4 is C1-> Br-> NO > I-> trichloroacetate > benzoate > valerate >butyrate > proprionate > formate > acetate > lactate > benzenesulfonate > isethionate > methylsulfonate > glutamate > cystea… Show more
“…The muscle lactate concentration linearly related to that in the bath, with a ratio of distribution between muscle water and medium of about 0 3. If these results indicate that the lactate distribution between fibre water and external fluid was also nearly independent of external concentration, they are in agreement with the data of (Woodbury & Miles, 1973); it seems reasonable to assume that the mammalian fibre membrane is also permeable to lactate. On the basis of the observations reported here, exclusive permeation of lactate ions was ruled out in favour of one of lactic acid molecules.…”
Section: Resultssupporting
confidence: 87%
“…Strictly, steady state will not be reached until EH = V. The increase in pHi without lactate, at high K, as compared to normal K (first line, Table 7) might well have been due to efflux of CO. combined with influx of bicarbonate, a mechanism entirely comparable to the lactic acid-lactate exchange. Woodbury & Miles (1973) showed that the ions of several weak acids with pKs of 4-87 or less are able to penetrate the membrane; their protonated forms are undoubtedly also permeable. Eqn.…”
SUMMARY1. The steady-state distribution ratios of D-and L-lactate between fibre water and external fluid were measured in 'intact' rat hemidiaphragm preparations exposed for 2-5 hr to a variety of solutions of normal ionic strength and osmolarity. The 11. This extrusion is insensitive to ouabain, as judged from the lack of effect of the drug on pHi with acid loading.
“…The muscle lactate concentration linearly related to that in the bath, with a ratio of distribution between muscle water and medium of about 0 3. If these results indicate that the lactate distribution between fibre water and external fluid was also nearly independent of external concentration, they are in agreement with the data of (Woodbury & Miles, 1973); it seems reasonable to assume that the mammalian fibre membrane is also permeable to lactate. On the basis of the observations reported here, exclusive permeation of lactate ions was ruled out in favour of one of lactic acid molecules.…”
Section: Resultssupporting
confidence: 87%
“…Strictly, steady state will not be reached until EH = V. The increase in pHi without lactate, at high K, as compared to normal K (first line, Table 7) might well have been due to efflux of CO. combined with influx of bicarbonate, a mechanism entirely comparable to the lactic acid-lactate exchange. Woodbury & Miles (1973) showed that the ions of several weak acids with pKs of 4-87 or less are able to penetrate the membrane; their protonated forms are undoubtedly also permeable. Eqn.…”
SUMMARY1. The steady-state distribution ratios of D-and L-lactate between fibre water and external fluid were measured in 'intact' rat hemidiaphragm preparations exposed for 2-5 hr to a variety of solutions of normal ionic strength and osmolarity. The 11. This extrusion is insensitive to ouabain, as judged from the lack of effect of the drug on pHi with acid loading.
“…The anion permeability and conductance sequences in these muscle fibers at pH 3.9 were found to be approximately the reverse of one another . Anion permeability and conductance sequences are essentially identical in frog skeletal muscle at pH 7.7 (Woodbury and Miles, 1973) and chloride conductance is increased at high pH (Hutter and Warner, 1967). Current-voltage relations during anion substitution (pH 7.6) in the present study showed no definitive conductance sequence.…”
A B S T R A C T Anionand cation permeabilities in dark-adapted Balanus photoreceptors were determined by comparing changes in the membrane potential in response to replacement of the dominant anion (Cl-) or cation (Na ÷) by test anions or cations in the superfusing solution. The anion permeability sequence obtained was PI > Pso~ > PBr > PCl > eisethionate > Pmethanesulfonate. Gluconate, glucuronate, and glutamate generally appeared more permeable and propionate less permeable than CI-. The alkali-metal cation permeability sequence obtained was PK > Pab > Pcs > PNa ~ PLi. This corresponds to Eisenman's sequence IV which is the same sequence that has been obtained for other classes of nerve cells in the resting state. The values obtained for the permeability ratios of the alkali-metal cations are considered to be minimal. The membrane conductance measured by passing inward current pulses in the different test cations followed the sequence, GK > GRb > Gcs > GNa > GIj. The conductance ratios obtained for a full substitution of the test cation agreed quite well with permeability ratios for all the alkali-metal cations except K + which was generally higher.
“…n = 4). This is about 3 times the value for the conductance ratio found in frog muscle, where there is known to be little interference between propionate and chloride (Woodbury & Miles, 1973). Combining this ratio with Dipolo's (1972) value for PC1 in barnacle muscle (1.9 x 10-6 cm/sec; no surface area correction), which is similar to PC, in crab muscle (A. P. Sharp, unpublished observations), gives a minimum value for the propionate anion permeability of approximately 6 x 10-8 cm/sec.…”
Section: Resultsmentioning
confidence: 55%
“…Such changes in intracellular pH (pHi) have been thought to account for some of the effects observed when the anions of weak acids are used to replace chloride (Woodbury & Miles, 1973;Kenyon & Gibbons, 1977;Marrannes & De Hemptinne, 1978). More recently, experiments in mammalian skeletal and cardiac muscle, using pH sensitive micro-electrodes, have shown pHi changes with the anions 72 A. P. SHARP AND R. C. THOMAS metabolic product) and salicylate (among other things, known to alter surface charge properties) which we considered interesting in their own right.…”
SUMMARY1. Intracellular pH (pHi) was measured in crab muscle fibres using pH-sensitive micro-electrodes. The mean stable pHi was 7-19+0-02 (S.E. of mean) and the corresponding mean membrane potential was -64-6+ 04 mV (S.E. of mean) at an external pH of 7-5.2. The effects on pHi of replacing 20 % (100 mM) of the external NaCl by the Na salts of various anions were examined. The anions of weak acids (pK'a > 4 5) caused large internal acidifications. The anions of strong acids (pK'a < 2-6) caused little or no change in pHi. The anions of acids with an intermediate pK' had varied effects on pHi. In particular salicylate (pK' = 2 97) was found to cause a large fall in pHi.3. Increasing the external pH reduced the effects of the anions of weak acids on pHi. It is argued that these effects are the result of the entry and subsequent dissociation of undissociated acid molecules.4. The results with propionate were quantified by comparing them with the effects of 5 % CO2 andwere found to be smaller than expected. It is suggested that this is the result of substantial membrane permeability to the propionate anion.
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