Influence of surface pH on intracellular pH regulation in cardiac and skeletal muscle

Abstract

The influence of the surface pH (pHs) on the intracellular pH (pHi) and the recovery of pHi after an imposed intracellular acid load was investigated in isolated sheep cardiac Purkinje fiber, rabbit papillary muscle, and mouse and rat soleus muscle. pHs and pHi, respectively, were continuously measured by use of single- and double-barreled pH-sensitive glass microelectrodes. Surface acidosis, usually obtained by superfusion with solutions of acid pH, was also produced with low buffered (5 mM N-2-hydroxyethylpiperazine-N'-2-ethane-sulfonic acid) solutions at control pH. The pHs decrease (delta pHs) induced by low buffering was smallest (-0.08 pH unit) in Purkinje fiber and largest (-0.31 pH unit) in rat soleus muscle, which already had a more acid surface in control conditions. delta pHs was somewhat dependent on the superfusion rate. Higher superfusion rates decreased but did not abolish delta pHs. Surface acidosis was associated with a small intracellular acidification. Intracellular acid loads were produced by adding and subsequently withdrawing 20 meq/l NH4+ from the superfusate. In all preparations, the rate of recovery of pHi after NH4+ withdrawal was notably decreased at acidified pHs. This effect was amiloride sensitive. It is concluded that, in superfused multi-cellular preparations, pHs and therefore the buffer concentration of a superfusate can considerably influence steady-state pHi and pHi recovery from an imposed intracellular acid load.

Extracellular carbonic anhydrase activity facilitates lactic acid transport in rat skeletal muscle fibres

“…Watt et al (1988) and Gladden et al (1995) reported that cinnamate leads to a reduction in lactate transport by 30 and 70 %, respectively, in a group of perfused muscles. Studies on soleus from mouse and rat (Vanheel et al 1986;Madureira & Hasson-Voloch, 1988;Juel & Wibrand, 1989;McDermott & Bonen, 1994) demonstrated an inhibition of lactate transport by 4-5 mM cinnamate of between 22 and 55 %. The greatest inhibitory effect of 69 -90 % by 10 mM cinnamate was observed in studies using sarcolemmal vesicles (Roth & Brooks, 1990aMcDermott & Bonen, 1993Juel, 1997).…”

pH recovery from intracellular alkalinization in Retzius neurones of the leech central nervous system.

“…The pHo influences not only pHi (Thomas, 1974;Deitmer & Ellis, 1980;Kettenmann & Schlue, 1988), but also pHi recovery from acidification (Boron, McCormick & Roos, 1979;Grinstein, Cohen & Rothstein, 1984;Vanheel, de Hemptinne & Leusen, 1986). The influence of pH.…”

“…), steady-state pHi and the rate of pHi recovery from intracellular acid loads in isolated sheep cardiac Purkinje fibre, rabbit papillary muscle, and mouse and rat soleus muscle (Vanheel et al 1986). To find out if extracellular buffering power influences the rate of pHi recovery from intracellular alkalinization Retzius neurones were alkaline loaded in weakly and strongly buffered solutions (Fig.…”

“…Purkinje fibre, rabbit papillary muscle, and mouse and rat soleus muscle (Vanheel et al 1986). The technique we applied to measure pH.…”

Intracellular pH of canine subendocardial Purkinje cells surviving in 1-day-old myocardial infarcts.

“…This muscle, which is not present in the preparation from infarcted hearts, 9 -12 may be an additional source of surface acidity. The H + leaving the ventricular muscle cells, which is not bound by extracellular buffers, will diffuse toward the surface of the preparation 34 and augment the surface acidity. When Purkinje fibers are made acutely hypoxic, there is a clear increase in the rate of generation of acid equivalents, which causes a decrease in both pHj and pH, 18 -24 (also, authors' unpublished results).…”