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K-Cl cotransport can participate in volume regulation in a number of cell types. Swelling activation of K-Cl cotransport in sheep erythrocytes proceeds by a two-step process, A<-->B<-->C (Dunham et al., J. Gen. Physiol. 101: 733-765, 1993). The A state, with a low flux, predominates at physiological volume. A-->B is rate limiting and can be activated by(More)
Activation of K-Cl cotransport is associated with activation of membrane-bound serine/threonine protein phosphatases (S/T-PPases). We characterize red blood cell S/T-PPases and K-Cl cotransport activity regarding protein phosphatase inhibitors and response to changes in ionic strength and cell size. Protein phosphatase type 1 (PP1) activity is highly(More)
We have investigated the possibility that the generation of hydrogen peroxide (H2O2) by spermatozoa plays a physiological role during capacitation. Capacitation is defined as the incubation period required for fertilization in mammals. Capacitation culminates in an exocytotic event, the acrosome reaction (AR). Mammalian sperm generate H2O2 during aerobic(More)
Total superoxide dismutase (SOD) and manganese superoxide dismutase (Mn SOD) specific activities were measured in tissue homogenates and in isolated mitochondria from normal rat liver and three Morris hepatomas of different growth rates. Total SOD and Mn SOD specific activities were decreased in all tumor homogenates when compared to normal liver; the(More)
Indirect evidence has suggested that K-Cl cotransport in human and sheep erythrocytes is activated physiologically by a serine-threonine phosphatase. It is activated experimentally by H2O2 and by staurosporine, a kinase inhibitor. Activation by H2O2 and staurosporine is inhibited by serine-threonine phosphatase inhibitors, suggesting that the activators(More)
We describe in this paper studies on the modes of operation of ouabain-insensitive sodium transport systems in red cells of normotensive and hypertensive patients. We have extensively investigated the properties of Na countertransport and cotransport in order to clarify whether they are two different proteins or one transport protein with two modes of(More)
This paper reports the presence of human red cells of an additional ouabain-insensitive transport pathway for lithium ions, the Li-K cotransport. Several kinds of observations support this conclusion. Cells loaded to contain only K, Na, or Li do not exhibit furosemide-sensitive efflux. Simultaneous presence of K and Li on the same side of the membrane(More)
K-Cl cotransport is involved in volume regulation in a number of cell types. Cell swelling stimulates K-Cl cotransport, probably by inhibition of a volume-sensitive kinase. K-Cl cotransport can also be activated by oxidants and thiol reagents. We investigated the effect of H2O2 on K-Cl cotransport of LK sheep red blood cells in an attempt to identify the(More)
By means of both direct assay and gel electrophoresis, normal A/J mouse liver was shown to possess both Cu-Zn and Mn superoxide dismutase (SD) activity. H6 hepatoma cells contained Cu-Zn SD activity, but no Mn SD activity was detectable. Isolated mitochondria from normal liver contained both forms of the enzyme, but isolated mitochondria from H6 hepatoma(More)
The effects of ethanol on locomotor activity and rotarod performance were measured in the rat. Apomorphine (4 mg/kg s.c.) antagonized and pimozide (0.75–1.50 mg/kg s.c.) enhanced the effects of a 2 g/kg dose of ethanol on rotarod performance. No such interaction was seen with pentobarbital, 25 mg/kg, a dose sufficient to produce an equivalent motor(More)