title: Cytoplasmic pH recovery in acid-loaded haemocytes of squid (Sepioteuthis lessoniana).
abstract: Cytoplasmic pH (pHi) of haemocytes of bigfin reef squid (Sepioteuthis lessoniana Lesson) was determined with the fluorescent probe, 2',7'-biscarboxyethyl-5,6-carboxyfluorescein (BCECF). The pHi of haemocytes suspended in nominally HCO3(-)-free medium (extracellular pH 7.4) averaged (+/- S.E.) 7.32 +/- 0.02. Intracellular pH was independent of external Na+ concentration and varied only slightly with changes in extracellular pH (pHe) (delta pHi/delta pHe = 0.16 over the pHe range 6.8-7.8). Addition of weak acids (sodium propionate, potassium acetate) to haemocyte suspensions resulted in a rapid decrease in pHi. Haemocyte pHi then recovered with an average half-time of 3-4 min. Recovery of pHi was independent of external Na+ concentration and insensitive to amiloride, but was abolished by N-ethylmaleimide (NEM). These results argue against the involvement of plasma membrane Na+/H+ exchange or other Na(+)-dependent transport mechanisms in the pHi recovery of acid-loaded haemocytes. The results suggest that there is an NEM-sensitive proton extrusion mechanism in the plasma membrane of squid haemocytes.
authors.affiliation: Department of Internal Medicine, University of Texas Medical Branch, Galveston 77550.
authors.forename: T A
authors.initials: TA
authors.lastname: Heming
authors.forename: C G
authors.initials: CG
authors.lastname: Vanoye
authors.forename: S E
authors.initials: SE
authors.lastname: Brown
authors.forename: A
authors.initials: A
authors.lastname: Bidani
mesh_terms: D000136:Acid-Base Equilibrium; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001773:Blood Cells / Q000502:physiology*; D003593:Cytoplasm / Q000502:physiology*; D049832:Decapodiformes; D005033:Ethylmaleimide / Q000494:pharmacology; D005456:Fluorescent Dyes; D006434:Hemocytes / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D012964:Sodium / Q000494:pharmacology
chemical_list: D005456:Fluorescent Dyes; D000584:Amiloride; D012964:Sodium; D005033:Ethylmaleimide