ROLE OF EXTRACELLULAR AND INTRACELLULAR PH CARP SPERM MOTILITY AND MODIFICATIONS BY HYPEROSMOSIS OF REGULATION OF THE NA+ H+ EXCHANGER/

Recently developed flow cytometric methods (Tron et al.: Mol Immunol 2 7:1307-1311, 1990) to measure the intracellular pH (pH(i)) and intrace llular potassium concentration in mammalian cells by using the fluores cent pH-indicator dye ,7bis-(2-carboxyethyl)-5(and-6)-carboxyfluoresce in (BCECF) were adopted for measuring these parameters in carp sperm. The intracellular potassium concentration of the carp sperm was 62.4 /- 5.3 mM. This is very similar to the potassium concentration of the seminal plasma (87 +/- 16 mM), and it suggests a depolarized state of the sperm cell in the semen. An average pH(i) value of 7.06 +/- 0.11 w as obtained by measuring sperm samples taken from ten animals. Changes in the ionic composition of the environment did not alter pH(i). Sper m motility was initiated by transferring the cells to an environment o f 110 mOsm osmolality. This hypoosmotic shock induced fast changes in the membrane structure that could be reversed by restoring physiologic osmolality. Activation was accompanied by a fast alkalinization of th e sperm cells. This pH change was amiloride sensitive, suggesting the involvement of the Na+/H+ exchanger in the activation process, Alkalin ization of acid-loaded sperm cells depended on the osmolality of the e nvironment. Equilibrium pill of these cells in hyperosmotic buffers wa s substantially lower relative to cells in an isoosmotic environment. Effects of the extracellular and intracellular pH on carp sperm motili ty were also examined. Extracellular pH below 5.5 abolished sperm moti lity completely, Alkaline extracellular pH did not alter the duration of sperm motility even at extreme values (pH(e) = 9.6), Duration of th e flagellar motion did not depend on the pH(i) between values of 6.5 a nd 8.5; however it was significantly reduced both below and above this range, No motility was observed below pH(i) = 6.0 or above pH(i) = 9. 5 with a 10 min incubation time at these pH values prior to activation , Effects of the extracellular and intracellular pH on sperm motility were partially reversible. (C) 1997 Wiley-Liss, Inc.