Comparison of Metabolic Effect of Ammonia and Adrenaline Infusions in Sheep

Abstract

It was found in previous experiments that an increased concentration of ammonia in the blood of sheep caused changes of the level of certain blood metabolites (glucose, lactate, pyruvate and free fatty acids) similar to those induced by adrenaline [Barej, Garwacki, Kulasek and Wiechetek, 1974; Wiechetek, Garwacki and Barej, 1975]. It was suggested from these findings that the ammonium ions might stimulate release of catecholamines which in turn could produce the metabolic changes observed. This suggestion has also been made by Feldman and Lebovitz [1971] and Prior, Clifford, Gibson and Visek [1971].The effect of adrenaline can be eliminated or markedly reduced by application of substances blocking adrenergic receptors. Wiechetek, Garwacki and Barej [1975] studied the metabolic effect of ammonium chloride in sheep after the infusion of phentolamine, an oc-receptor blocking agent. Blockade of areceptors prevented the hyperglycaemnic response to both ammonia and adrenaline infusions. The blockade did not greatly influence the effect of either substance on lipid mobilization.It was suggested by Basset [1970] and Himms-Hagen [1972] that the lipolytic effect of adrenaline in sheep is mainly exerted through the /B-adrenergic receptor activity. It was the purpose of the present study to determine the effects of ammonium ions and adrenaline on the level of some blood metabolites of sheep after administration of propranolol as a /3-receptor blocking agent. MethodsThe experiments were carried out on 24 individually fed Merino-Precose ewes weighing 50-55 kg receiving a concentrate ration which consisted of ground 23

Effects of Increased Blood Ammonia Concentrations on the Concentrations of Some Metabolites in Rat Tissues

“…It is not known, however, whether ammonia loading affects the metabolism of different tissues in the same manner and how such effects are mediated. Feldman & Lebowitz (1971), Prior et al (1971 and Barej et al (1974) suggested that higher secretion of catecholamines was involved but Wiechetek et al (1975) andGarwacki et al (1979) (1975) and Garwacki et al (1979). The present results show again that different tissues react to hyperammoniaemia in different ways.…”

“…Recently Wiechetek et al (1979) demonstrated that elevated ammonium ion concentrations stimulated adenylate cyclase activity in vitro in brain but not in liver, fat and muscle tissue. Therefore the metabolic effects of ammonia cannot generally be attributed to an increase of cyclic AMP as was suggested earlier by Wiechetek et al (1975) and Garwacki et al (1979). The present results show again that different tissues react to hyperammoniaemia in different ways.…”

“…Concentrations of cyclic AMP showed a small but insignificant increase. (Chow, Pond & Walker, 1970;Hindfelt & Siesj6, 1970;Prior, Clifford, Gibson & Visek, 1971;Barej, Garwacki, Kulasek & Wiechetek, 1974;Wiechetek, Garwacki & Barej, 1975;Garwacki, Wiechetek & Barej, 1979) ammonia loading results in higher blood levels of glucose, pyruvate, lactate and free fatty acids and in reduced glycogen concentrations in various tissues. These changes have been attributed to either increased glycogenolysis without stimulation of glucose utilization, or to a reduction of glucose oxidation in the body tissues.…”

“…It is not known, however, whether ammonia loading affects the metabolism of different tissues in the same manner and how such effects are mediated. Feldman & Lebowitz (1971), Prior et al (1971) and Barej et al (1974) suggested that higher secretion of catecholamines was involved but Wiechetek et al (1975) and Garwacki et al (1979) showed that blockade of ax-and fl-receptors did not completely abolish the metabolic effects of ammonia. Recently Wiechetek et al (1979) demonstrated that elevated ammonium ion concentrations stimulated adenylate cyclase activity in vitro in brain but not in liver, fat and muscle tissue.…”

Subclinical ammonia toxicity in steers: effects on hepatic and portal-drained visceral flux of metabolites and regulatory hormones.

“…Hyperammonemia has been associated with derangements in glucose metabolism in cattle (Spires and Clark, 1979;Symonds et al, 1981;Fernandez et al, 1988) and sheep (Barej and Harmeyer, 1979;Garwacki et al, 1979;Emmanuel et al, 1982; Orzechowski et al, 1988). The effects of elevated blood ammonia on circulating levels of insulin ( Barej and Harmeyer.…”