Amino acids antagonisms

Ennis, M., Jiang, M., Zimmer, L.A. and Shipley, M.T. (1994) Excitatory amino acid antagonism blocks sensory evoked excitation of rat mitral cells in vitro. A.Chem.S. Abstr, 16, 257. 

Despite the similarity of amounts administered (Table 4), the serum concentrations of threonine, valine, isoleucine, leucine and lysine were clearly different in Test Series I and II (Figure 7). Amino acid imbalances and/or amino acid antagonisms have to be assumed to be the reason (Greenstein and Winitz, 1961 Harper,... 

Atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) are members of a family of so-called natriuretic peptides, synthesized predominantly in the cardiac atrium, ventricle, and vascular endothelial cells, respectively (G13, Y2). ANP is a 28-amino-acid polypeptide hormone released into the circulation in response to atrial stretch (L3). ANP acts (Fig. 8) on the kidney to increase sodium excretion and glomerular filtration rate (GFR), to antagonize renal vasoconstriction, and to inhibit renin secretion (Ml). In the cardiovascular system, ANP antagonizes vasoconstriction and shifts fluid from the intravascular to the interstitial compartment (G14). In the adrenal cortex, ANP is a powerful inhibitor of aldosterone synthesis (E6, N3). At the hypothalamic level, ANP inhibits vasopressin secretion (S3). It has been shown that some of the effects of ANP are mediated via a newly discovered hormone, called adreno-medullin, controlling fluid and electrolyte homeostasis (S8). The diuretic and blood pressure-lowering effect of ANP may be partially due to adrenomedullin (V5). 

It is well recognized that interrelations exist. How much sodium one needs depends upon his potassium intake his calcium needs are determined in part by his phosphate intake his need for a specific amino acid may be determined in part by the amount of the other amino acids that he gets (they can interfere with each other s utilization). Only by further experimentation can we determine how important antagonisms and other interrelations are in human nutrition. If highly important, they will seriously complicate the picture but will not change its basic outlines. 

Glycine plays an important inhibitory role in the lower brain stem and spinal cord. Little is known about the synthesis of glycine. It activates a Cl- channel, which is antagonized by strychnine. Other endogenous amino acids may activate the glycine channel, such as taurine and j8-alanine. Neuropeptides... 

A) Antagonism of the inhibitory amino acid neurotransmitter glycine... 

Anabolic activities of testosterone, such as increases in amino acid incorporation into protein and in RNA polymerase activity, have been demonstrated in skeletal muscle. Apart from the direct anabolic effects in specific tissue, androgens antagonize the protein catabolic action of glucocorticoids. The androgen compounds with the greatest ratio of protein anabolic effects to virilizing effects are the 19-nortestosterone derivatives. Compounds that are used clinically (Table 63.3) include nandrolone phenpropionate (Durabolin), nandrolone decanoate... 

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