Red-cell pH in tench. Interacting effects of cellular nucleoside triphosphates, Hb-oxygenation and extracellular pH

Experimental adjustments of red-cell pH (pHi) by varying red-cell nucleoside triphosphate (NTP) content, blood oxygenation state and extracellular pH (pHe) demonstrated a tight interdependence of these variables in their influence upon pHi. The increase in pHi with deoxygenation (delta pHi (d--o] is large, but becomes strongly reduced when the NTP content is decreased and when pHe falls. Lowering of red-cell NTP increases pHi, notably at high pHe, but this NTP dependence of pHi (delta pHi/delta(NTP/Hb] is much smaller in deoxygenated than in oxygenated blood. The pHe dependence of pHi (delta pHi/delta pHe) increases upon reduction of red-cell NTP content and upon deoxygenation. The results are consistent with the view that pHi is governed by Donnan-like distribution of protons across the red-cell membrane, and show that a pronounced red-cell swelling accompanies increases in the distribution ratio [H+]e/[H+]i. The data are interpreted in terms of changes in the red-cell non-permeable charge as induced by NTP and its linkage with the haemoglobin proton equilibria.