title: Elevation of the intracellular pH activates respiration and motility of sperm of the sea urchin, Strongylocentrotus purpuratus.
abstract: The internal pH (pHi) of sperm of the sea urchin, Strongylocentrotus purpuratus, was estimated by measuring the accumulation of the weak bases [14C]methylamine, [14C]diethylamine, or 9-aminoacridine under conditions where cellular respiration was activated or inhibited. When 9-aminoacridine fluorescence measurements are corrected for binding to intracellular components, the pHi estimates agree quantitatively with those obtained from [14C]amine distributions. The pHi of sperm decreased when the intracellular [K+] was elevated above the physiological value of 10 mM, or when the external pH was substantially decreased below the physiological 8.0, or when Na+ was absent from the seawater. At the decreased pHi values, sperm respiration and motility were inhibited; conversely, both respiration and motility increased when the pHi was elevated. Increased respiration occurred whether the pHi was increased by altering the external pH, [K+] or [Na+], or by the addition of NH4Cl to the medium. In all cases, the activation of respiration and motility were linked, suggesting a unitary control mechanism, some possibilities for which are presented.
mesh_terms: D000818:Animals; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D008433:Mathematics; D009994:Osmolar Concentration; D010101:Oxygen Consumption; D012617:Sea Urchins; D013081:Sperm Motility; D013094:Spermatozoa / Q000502:physiology*