Adrenergic regulation of Rana balcanica erythrocyte pyruvate kinase.

The regulation of pyruvate kinase activity by noradrenaline was investigated in Rana balcanica red cells. Thirty minutes of noradrenaline incubation induced a significant increase in the Vo/Vmax ratio of pyruvate kinase. The S0.5 for phosphoenolpyruvate of the enzyme significantly increased in the presence of noradrenaline while the Km for ADP decreased. In response to hormonal stimulation the Na +/H+ exchange was activated as was shown by the increase in Na+ and cyclic adenosine monophosphate from the 3rd min of incubation. All these effects were specific to alpha1 and beta antagonists. High concentrations of fructose diphosphate significantly activated the enzyme in the presence of noradrenaline but not in its absence. Furthermore, the presence of noradrenaline partially released the inhibition of the enzyme by adenosine triphosphate, inorganic phosphate and 2,3-diphosphoglycerate. The results suggest that noradrenaline stimulates glycolysis through pyruvate kinase activation. The mechanism of stimulation may is through Na+/H+ exchange activation, cyclic adenosine monophosphate concentration and Na(+)-K(+)-ATPase activation.

Expression of the A-raf proto-oncogene in the normal adult and embryonic mouse.

We have determined the expression pattern of the A-raf proto-oncogene in the embryonic and adult mouse. Western blot analysis of protein lysates from tissues of adult mice show that p69A-raf is ubiquitously expressed, but that levels of expression vary among different tissues. To determine the cell-specific expression pattern of A-raf, we generated transgenic mice expressing the beta-galactosidase reporter gene from the A-raf promoter. We show that A-raf expression is highly specific within a given tissue, and we identify cell types expressing this gene in the adult testis, epididymis, vas deferens, seminal vesicle, ovary, oviduct, bladder, kidney, intestine, heart, spleen, thymus, and cerebellum. In the embryo, ubiquitous expression of the reporter gene is observed, but the highest levels of expression are specifically detected in the embryonic heart at stages 9.5-11.5 days post-coitum.

Influence of noradrenaline on the respiratory status of Rana balcanica red cell suspension under normoxia, hypoxia and hypercapnia: alpha 1-receptor involvement.

The effect of normoxia, hypoxia and hypercapnia on the extracellular pH, partial pressure carbon dioxide (pCO2), partial pressure oxygen (pO2) and HCO3- levels after noradrenaline treatment of Rana balcanica erythrocytes, was investigated. Noradrenaline caused a significant reduction of the extracellular pH which may have been due to the activation of red blood cell Na+/H+ exchange. Significant falls in the partial extracellular pressure of CO2 and O2 were evident. The initial reduction in extracellular pCO2 and pO2 was followed by a rise reflecting the desensitization of the Na+/H+ exchange after 15 min of hormone stimulation. Both hypercapnia and hypoxia increased the magnitude of these changes in relation to normoxia, although the greatest changes were observed under hypercapnic conditions. The involvement of alpha 1 receptors in regulating the concentration of respiratory gases after catecholamine stimulation was demonstrated. It is suggested that these responses increased the effectiveness of gas transfer over the respiratory surfaces.