Release of intracellular glycerol and pore formation in Dunaliella tertiolecta exposed to hypotonic stress

Abstract

FUJII, S., and HELLEBUST, J. A. 1992. Release of intracellular glycerol and pore formation in Dunaliella tertiolecta exposed to hypotonic stress. Can. J. Bot. 70: 1313-1318. When Dunaliella tertiolecta cells, previously cultured in a 0.5 M NaCl medium, were resuspended in a 0.25 NaCl medium, about 50% of the intracellular glycerol was lost within 2 min. A corresponding amount of glycerol appeared inthe medium, while other organic solutes, such as amino acids and sugars, were not detected. These results indicate that intracellular glycerol is rapidly released without significant concomitant cell damage. Rubidum, in the case of rubidium-loaded cells, was also rapidly teleased to the medium in response to hypotonic shock. Gramicidin, dimers of which form stable membrane pores, caused rapid release of intracellular glycerol, while the ionophore, valinomycin, had no effect. When 0.5 M NaC1-grown cells were resuspended in 0.25 M NaCl medium, intracellular trapping of 14C-glycerol occurred but not of I4C-glucose, 14C-sucrose, or I4C-glycine. However, when 0.5 M NaC1-grown cells were resuspended in 0.05 M NaCl medium, intracellular trapping of small amounts of '4C-glucose, 14C-sucrose, or I4C-glycine, in addition to considerable amounts of 14C-glycerol, occurred. These results indicate that abrupt hypotonic shocks cause transient formation of small nonspecific pores in the plasma membrane of D. tertiolecta cells and that intracellular glycerol is released to the medium through such nonspecific transient pores.Key words: Dunaliella, hypotonic shock, glycerol release, rubidum, pore formation.FUJII, S., et HELLEBUST, J. A. 1992. Release of intracellular glycerol and pore formation in Dunaliella tertiolecta exposed to hypotonic stress. Can. J. Bot. 70 : 1313-1318. Lorsqu'on transfert des cellules de Dunaliella tertiolecta prkalablement cultivCes dans une solution 0,5 M en NaC1, dans un milieu contenant du NaCl 0,25 M, elles perdent environ 50% du glycCrol intracelulaire en moins de 2 min. On retrouve dans le milieu une quantitC correspondante de glycCrol, alors que les autres solutCs organiques, tels que les acides aminks et les sucres, en sont absents. Ces rCsultats indiquent que le glycCrol intracellulaire est rapidement reliche sans que les cellules soient au mCme moment blessCes. Dans le cas de cellules chargCes de rubidium, celui-~i est Cgalement rapidement reliche dans le milieu en rCaction au choc hypotonique. La gramicidine, dont les dimkres forment des pores membranaires stables, dCclenche un rellchement rapide du glycCrol intracellulaire, alors que l'ionophore valinomycine reste sans effet. Lorsqu'on resuspend des cellules prkalablement cultivCes en presence de NaCl0,5 M dans un milieu de NaCl0,25 M, on observe une skquestration intracellulaire du I4C-glycCro1, mais non du 14C-glucose, du 14C-sucrose ou de la I4C-glycine. Cependant, lorsqu'on resuspend des cellules prkalablement cultivies en prCsence de NaCl 0,5 M dans un milieu de NaCl 0,05 M, on observe une ~Cquestration intracellulaire de petites quantitCs de 14...

Growth and osmoregulation of Boekelovia hooglandii in relation to salinity

“…This method was found to be as efficient as the extraction of cells with 80% aqueous ethanol for 10 min at 60°C (data not shown) and eliminated an additional liquid -liquid extraction step to remove pigments. Total amino acid contents of aliquots of the supernatant of centrifuged extracts (20000 X g for 10 min) were determined by the ninhydrin method (8). L-Leucine was used as a standard for calibration of the method.…”

What does a Common Channel for Electrolytes and Non-electrolytes in the Sperm Mean?

“…In the halophile, Dunaliella, which has both 422 V. SITARAMAM AND Z. E. SAUNA (Fujii & Hellebust, 1992). Similarly, a variety of the socalled osmoprotectants, ionic and non-ionic, can be considered to modulate the internal ionic content by their own preferential #uxes (Csonka & Hansen, 1991;Reed et al, 1987).…”

Effect of Ca2+ on the retention of glycerol and amino acids in Dunaliella tertiolecta

“…In this case, the glycerol leakage was not reduced because the leakage is due to the permanent pore formed on the plasma membrane by gramicidin. However, the glycerol leakage in response to an abrupt down shock was immediately reduced (Gilmour et al 1984;Zidan et al 1987;Fujii & Hellebust 1992). The best explanation for this phenomenon is probably the occurrence of a transient pore on the plasma membrane in Dunaliella formed by an abrupt down shock (Fujii & Hellebust 1992).…”

“…The low permeability of plasmalemma for glycerol was reported to be disturbed when cells were subjected to high temperatures (Wegmann, Ben-Amotz & Avron 1980) or an abrupt down shock Correspondence: Shuhei Fujii, Laboratory of Biology, Tezukayama College, 3-1-3, Gakuen minami, Nara, 631 Japan. (Gilmour, Hipkins & Boney 1984;Zidan, Hipkins & Boney 1986;Fujii & Hellebust 1992). Furthermore, numerous studies have examined effects of Ca^"*" on the maintenance of membrane integrity (Welch & Epstein 1969;Stevenink 1965;Bisson 1984).…”

“…In addition to that, spermine reduces the leakage of intracellular solutes in D. tertiolecta. Fujii & Hellebust (1992) reported that the application of gramicidin caused the leakage of intracellular glycerol but not intracellular amino acids. In this case, the glycerol leakage was not reduced because the leakage is due to the permanent pore formed on the plasma membrane by gramicidin.…”