P45 LYALINEANTAGONISES THE INFLUENCE OF AMMONOA: EXPERIMENTAL AND HUMAN BRAIN STUDIES: P.Riederer, E.Kienzl, K.Jellinger, G.Klein- ber er. Boltzmann Inst.Clin.Neurobiol. Lainz-Hospital, I.Univ. z+l c oo of Med.. Vienna. Austria.

As serotonin (5-Hi) synthesis and turnover are enhanced in he- patic encephalopathy (HE) postsynaptic 5-HT-receptor binding was measured (Scatchard analysis; method) (1). The in vitro effect of L-Valine (VAL) and ammonia (NH ) using different concentrations after preincubation (10') was stu $. led in post mortem frontal cor- tex homogenates of patients with hepatic coma and matched controls. Table shows a decrease of 5-HT receptor density in HE, whereas the affinity of the ligand (KD) is increased. In vitro experiments show similar effects with NH4.. Low concentrations (O.lmM) of VAL antagonize the NH effect in vitro (table) and ex vivo (2). 5-HT receptor binding ? s more sensitive to VAL in HE as compared to con- trols. It is concluded that VAL modulated 5-HT receptors in HE which may contribute to its beneficial action in the treatment of HE. (1) Bennett, J.P., Snyder, S., Brain Res. 94,523-544 (1975), (2) Riederer, P.er al, Neuroscience 7,Supll. 177 (1982).

NH4 VAL BMax (fmol/mg prot)est. KD(nM) BMax(fmol/mg PrOt) KD

nm nm high aff.spec.bind% % total spec.bind% (nM)%

Controls(60) - - 100 100 100 100 10 - 45 54 64 40 10 15 95 136 98 87 30 - 30 1

345; 3:: 75 67 112 174

30 15 340 371 135 202 30 60 235 430 99 70

Hepatic Coma (60) E -

E 0.1 68*(=100) 51*(=100) 58*(=100) 30*(=100) 180 303 125 365

E 15 70 263 70 357 E 30 0 0 34 253

means ( ) number of estimations/given value; *compared to controls; =lOO% value of coma calculations; E=endogenous NH,+ (range 4.3 - 5.2 pmol/g).

L-LEUCINE PREVENTS AMMONIA-INDUCED MODULATION OF GLUTAMINE RECEPTORS IN THE BRAIN. P.Ferenci and E.A.Jones. Liver Unit, NIADDK, NIH, Bethesda, Maryland, USA.

Increased brain levels of ammonia are considered to potentiate hepatic encephalopathy (HE), whereas branched chain amino acids (BCAA), administe- red by intravenous infusion, appear to induce an amelioration of HE in pa- tients with chronic liver disease. These phenomena may be associated with changes in the functional status of neurotransmitter systems in the brain. To investigate this possibility the effects of ansaonia alone and ammonia together with a BCAA, L-leucine, on the binding of the excitatory neuro- transmitter, glutamate, to postsynaptic neurons in the brain were studied. Over a 3 h period rabbits received intravenous infusions of normal saline or ansnonium chloride (2.2 nsnol/h) with or without L-leucine (0.4 g/kg/h). At the end of the infusion crude synaptic membranes were prepared from the hippocampus and, using 3H-glutamate as the ligand, the affinity (KD) and density (Bmax) of binding sites on the membranes were determined. Results are expressed as mean + SEM:

Infusion n Kg (nM) B max (pmol/mg protein)

Normal saline 9 975 + 138 110 + 16 Ammonia 8 609 i 102* 206 : 31* Ammonia + L-leucine 4 920 i 106** 138 - 33 *= p 10.05 vs. controls **= pL 0.05 vs ammonia Additional control experiments indicated that neither amnonia nor L-leu- tine affect the binding of 3H-glutamate to neural membranes per se. Thus, the changes in KD and Bmax induced by ammonia in vivo reflect arrmonia-in- duced changes in the metabolism of the glutamate neurotransmitter system, possibly a depletion of the glutamate neurotransmitter pool. The results of this study suggest that ammonia may influence neural function in HE by modulating neurotransmission and that amelioration of HE by BCAA may be mediated, at least in part, by BCAA counteracting ammonia-induced chan- ges in neurotransmission.

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