The control of Na+/H+ exchange by molecular oxygen in trout erythrocytes. A possible role of hemoglobin as a transducer.

Abstract

A B S T R A C T It has previously been shown that addition of catecholamines to a suspension of trout erythrocytes induces an enlargement of the cells owing to an uptake of NaC! mediated by a cAMP-dependent, amiloride-sensitive Na+/ H + exchange. In this article, we show that the change in cell volume induced by catecholamines is much greater when the erythrocytes are incubated in N2 than when they are in 02. This difference is explained by an inhibition of the cAMP-dependent Na+/H + exchange by 02. The inhibition is not reversed in cells incubated in O~ but poisoned with cyanide. It cannot be explained by a difference in the content of cAMP in O~ and in N~. In a CO atmosphere, in which the cells are anoxic, swelling and Na permeability are not increased as they are in N~: in CO, the cells behave as they do in O~. Moreover, cells previously exposed to CO and then put in an N~ atmosphere do not show the expected increase in Na+/H + exchange. This strongly indicates that the binding of CO to hemoglobin, which persists during the subsequent exposure to N~, is the primary event responsible for the inhibition. As CO substitutes for O~ in binding to hemoglobin, the effect of O~ in the control of Na+/H + exchange is probably explained by this interaction with heine. (Allen and McManus [1968.

Dynamics of the content of H2O, Na, K, Ca and Mg in the eggs of bream, Abramis brama L. in natural conditions and under stress

“…Similar mechanism is discovered in adaptation of fishes to lack of oxygen in the water. It is shown that in condition of hypoxia and rise of outside temperature, increase of Na ions level accompanied by water absorption occurs in erythrocytes [52][53][54][55]. Consequently, the volume of erythrocytes increases resulting in increase of their oxygen bearing volume due to additional capture of oxygen [56].…”

“…Consequently, the volume of erythrocytes increases resulting in increase of their oxygen bearing volume due to additional capture of oxygen [56]. It is believed that increase in the content of Na ions in erythrocytes in condition of adapting of fishes to lack of oxygen is connected with amplification of activity of Na + /H + transporter [52,53]. Perhaps, this ionic pump also participates in increasing concentration of Na ions in oocytes during their transition from maturity Stage IV to V. To prove this, additional studies of oocytes in vitro are necessary.…”

The Na + /H + Exchanger Present in Trout Erythrocyte Membranes is Not Responsible for the Amiloride-insensitive Na + /Li + Exchange Activity

“…(A) is the NaVH^ exchanger pNHE, which, as indicated by the equal sign can also exchange Li* for H+. (B) is the protein respon sible for the DMA insensitive Na+/Li+ exchange activity, isopr = isoproterenol, (3 = (3 adrenergic receptor, PKA = protein kinase A, proterenol and inhibited by either DMA or 0 2 (Borggreven et aL, 1995) and therefore can be attributed to the trout erythrocyte Na+/H+ exchanger, ^NHE (Motais, Garcia-Romeu & Borgese, 1987;Motais et ah, 1990;Borgese et al, 1992;Guizouarn et al, 1993). The Na+/ Li+ exchange activity in these membranes, however, was not influenced by either of these components (Borggreven et aL, 1995).…”

Effect of catecholamines on deformability of red cells from trout: relative roles of cyclic AMP and cell volume.

“…The addition of catecholamines to a trout red blood cell suspension promotes a large increase in cell volume (Baroin, Garcia-Romeu, Lamarre & Motais, 1984a;Bourne & Cossins, 1982;Nikinmaa, 1982;Borgese, Garcia-Romeu & Motais, 1987 a) as a result of an accumulation of sodium and chloride, part of the entering sodium then being rapidly exchanged for potassium via the sodium-potassium pump (Baroin et al 1984a).…”

“…when a trout is submitted to a deep and rapidly developed hypoxia, a welldefined metabolic acidosis occurs which is due to the ,J-adrenergic-controlled release of H+ from crythrocytes via the Na+-H+ exchanger , and simultaneously the haemoglobin oxygen affinity is increased (Tetens & Lykkeboe, 1985; Claireaux, and (3) the activity of the Na+-H+ exchanger is controlled by the partial pressure of oxygen in the saline. This control is triggered by the binding of molecular oxygen to haeme which, via the modification in the quaternary structure of the haemoglobin molecule, could affect the exchanges (Motais, Garcia-Romeu & Borgese, 1987). This control of Na+-H+ exchanges by the partial pressure of oxygen in the blood appears as a regulatory loop in a process serving to increase the carrying capacity of erythrocytes for oxygen in deep hypoxia.…”