K+/H+ antiport in heart mitochondria.
نویسندگان
چکیده
Heart mitochondria depleted of endogenous divalent cations by treatment with A23187 and EDTA swell in (a) K+ acetate or (b) K+ nitrate when an uncoupler is present. These mitochondria also exchange matrix 42K+ with external K+, Na+, or Li+ in a reaction that does not require respiration and is insensitive to uncouplers. Untreated control mitochondria do not swell in either medium nor do they show the passive cation exchange. Both the swelling and the exchange reactions are inhibited by Mg2+ and by quinine and other lipophilic amines. Swelling and exchange are both strongly activated at alkaline pH, and the exchange reaction is also increased markedly by hypotonic conditions. All of these properties correspond to those reported for a respiration-dependent extrusion of K+ from Mg2+-depleted mitochondria, a reaction attributed to a latent Mg2+- and H+-sensitive K+/H+ antiport. The swelling reactions are strongly inhibited by dicyclohexylcarbodiimide reacted under hypotonic conditions, but the exchange reaction is not sensitive to this reagent. Heart mitochondria depleted of Mg2+ show marked increases in their permeability to H+, to anions, and possibly to cations, and the permeability to each of these components is further increased at alkaline pH. This generalized increase in membrane permeability makes it likely that K+/H+ antiport is not the only pathway available for K+ movement in these mitochondria. It is concluded that the swelling, 42K+ exchange, and K+ extrusion data are all consistent with the presence of the putative K+/H+ antiport but that definitive evidence for the participation of such a component in these reactions is still lacking.
منابع مشابه
Matrix free Mg2+ and the regulation of mitochondrial volume.
Mitochondria must maintain volume homeostasis in order to carry out oxidative phosphorylation. It has been postulated that the concentration of free Mg2+([Mg2+]) serves as the sensor of matrix volume and regulates a K+-extruding K+/H+antiport (K. D. Garlid. J. Biol. Chem. 255: 11273-11279, 1980). To test this hypothesis, the fluorescent probe furaptra was used to monitor [Mg2+] and free Ca2+ co...
متن کاملMatrix magnesium and the permeability of heart mitochondria to potassium ion.
Isolated beef heart mitochondria were treated with A23187 in the presence of different concentrations of Mg2+ or EDTA to establish varying levels of total mitochondrial Mg2+. The Mg2+ content was related to the rate of passive swelling of the mitochondria in potassium acetate and other potassium salts in which swelling is presumed to depend on K+ entry via an endogenous K+/H+ antiport. Swelling...
متن کاملIon transport processes in corn mitochondria : I. Effect of the local anesthetic dibucaine.
The local anesthetic dibucaine inhibited respiration-dependent contraction mediated by the K(+)/H(+) antiport system of isolated corn mitochondria. Respiration declined concurrently. Nigericin, an exogenous K(+)/H(+) exchanger, restored ion efflux in dibucaine-blocked corn mitochondria. It was concluded that dibucaine inhibited ion efflux via blockage of the K(+)/H(+) antiport. Further experime...
متن کاملEvidence for the allosteric regulation of the mitochondrial K+/H+ antiporter by matrix protons.
It is well accepted that the mitochondrial K+/H+ antiporter is regulated by matrix Mg2+; however, this is not the only factor controlling its activity. The precise conditions used to deplete divalent cations have profound effects on the subsequent activity of the antiporter in a KOAc assay medium. Examination of the proton fluxes during both pretreatment and subsequent assay of K+/H+ antiport r...
متن کاملL-Lactate transport into rat heart mitochondria and reconstruction of the L-lactate/pyruvate shuttle.
In vitro reconstruction of the L-lactate/pyruvate shuttle has been performed, which allows NADH oxidation outside rat heart mitochondria. Such a shuttle occurs due to the combined action of the novel mitochondrial L-lactate/pyruvate antiporter, which differs from the monocarboxylate carrier, and the mitochondrial L-lactate dehydrogenase. The rate of L-lactate/pyruvate antiport proved to regulat...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
- The Journal of biological chemistry
دوره 259 23 شماره
صفحات -
تاریخ انتشار 1984