CARDIOVASCULAR EFFECTS OF ADENOSINE IN MAN, Alf 199 Sollevi, Mikael Lagerkranser, Christer LindqGt, Lars Irestedt. Dept of Anesthesiology, Karolinska Hospital, Stockholm, Sweden. The effect of adenosine on central hemodynamics and cerebral blood flow were studied in 30 patients during anesthesia. The studies were approved by the local Ethics committ.4 and performed after informed consent. Hemodynamics were recorded by a Swan- Ganz catheter and an intraarterial cannula. Cardiac output was determined by the thermodilution technique and cerebral blood flow was quantified by positron-emission-tomography. Adenosine concentrations in plasma was determined by high pressure liquid chromatography. Adenosine infusion (0.05-0.3 mg/kg/min) induced a stable hypotension (mean arterial blood pressure, MABP 40-50 mmHg), corresponding to 40-50?; reduction of MABP, at an arterial adenosine concentration in the pmolar range (10-20 fold elevation of basals levals) . Dipyridamole pretreatment (0,3-0,4 mg/kg,klI) decreased the dose requirement for adenosine by 501 (p<0,01). Hy- potension was caused by a profound decrease in the systemic vas- cular resistance (61*3?;), while cardiac output increased by 40+ 5%. The myocardial'filling pressures were not affected by adeno- sine. The P-R interval of the ECG was significantly prolonged, indicating inhibition of atrioventricular conductance, more pro- minent after dipyridamole treatment. Whole body oxygen consump- tion was significantly decreased by 16L, without elevation of lactate levels. Adenosine induced a general increase in cerebral blood flow, during normoventilation (n:3), and in cortical areas the flow was increased 2-3 fold. Adenositie is a powerful dilator of the resistance vessels in man. --- ADENINE NUCLEOTIDE DEGRADATION IN THE HUMAN 200 MYOCARDIUM DURING CARDIOPLEGIA: if Sollevi, Walter Schmidt, Eva Jansson, Wollmer Bomfim, Lennart Kaijser. Department of Pharmacology, Karolinska Institut- et, and Department of Clinical Physiology, Karolinska Hospital, Stockholm, Sweden. Myocardial ischemia is associated with adenine nucleotide de- gradation and accumulation of nucleosidea and bases. Data regard- ing adenine nucleotide degradation in ischemic human myocardium is limited. The adenine nucleotides, IMP, adenosine, inosine, hy- poxanthine and uric acid were determined by high pressure liquld chromatography, in biopsies (1.5-4 mg) from human left ventricu- lar myocardium during cardioplegia (at 10-15'~) in six patients (aged 35-64 year) subjected to aortic valve replacement surgery. The study was performed after informed consent and approval from the Ethics CommitC. The first biopsy was collected after induction of cardioplegia and the second 45-60 min later. The myocardium was perfused with diluted cold blood 25-30 ml/min (with 20 mM po- tassium). The ATP concentration was 12.64+1.96 mmoles/kg dry muscle (d.m. ) after induction and decreased by 37+5% (p<D.01) . AMP ranged between 2 and 3 mmoles/kg d.m., while IMP was consis- tently low, (0.11+0.01 mmoles/kg d.m. 1. The adenosine concentra- tion was high, (OT26c0.04 mmol/kg d.m. 1, and inosine increased from 0.82 to 2.66 mmGles/kg (p<0.01). Approximately 3 mmoles/kg d.m. of purine material was probably washed out of tissue during the perfusion. In conclusion, cardioplegia is associated with severe ischemia and the major route fo AMP degradation is probably through adenosine. -- . RELEASE OF ADENOSINE FROM THE ISCHEMIC HUMAN HEART. 201 Alf Sollevi, Lennart Kaijser, Bertil B. Fredholm. Department of Pharmacology, Karolinska Institutet, Stockholm, Sweden. Adenosine is released from the mammalian heart during ische- mia. Yet, it has proven difficult to demonstrate adenosine release follo\ring coronary sinus (cs) catheterization in pacing- induced angina. In this study, dipyridamole (Dip, an inhibitor of adenosine uptake) was used to facilitate detection of adenosine release during myocardial ischemia. Methods: Seven patients with ischemic heart disease (IHO) and five healthy volunteers were studied by arterial (a) and cs catheterization, after informed consent and approval from the Ethics Commit&. Atrial pacing to angina or heart rate (HR) 150 (in volunteers) were performed be- fore and during continuous dipyridamole infusion (5 g/kg/min). Cs blood flow (CSBF, thermodilution technique), a-ccdifferences for adenosine and hypoxanthine (by high pressure liquid chromato- graphy), lactate and 0 were measured before, during and after pacing. Results: ~acinz increased CSBF (53% in IHO and 60% in volunteers) and O2 uptake. IHD released lactate and hypoxanthine but not adenosine. Dipyridamole (1-1.5 M in plasma) did not affect HR, BP or O2 uptake but increas& resting CSBF (18:;) in all subjects. During pacing, CSBF was enhanced in volunteefs but not in IHD, in comparison to control pace. The a-cs difference for adenosine (-0.17+0.06 M, p<0.05) was different from pre- pacing (p<0.01) in IRD. ~Goxanthinerelease tended to be even higher than during and after the control pacing, while the a-cs difference for adenosine and hypoxanthine were unaffected in vo- lunteers. In conclusion, angina causes release of adenosine. ACUTE ATTACK OF GOUT TRIGGERH) BY Maria L. Sorgi, A. Giacomello, A. Zoppini Acute attack of gout triggered by.allopurino1 has been studied by a retrospective analysis of 134 pa- tients with gout treated with this drug. The results suggest that: a) mobilization of tophaceous deposits in the joints play an important part in the pathogenesis af the acute attack of gout triggered by allopurinol. b) acute gouty attacks after the initiation of allopi rinol therapy are more frequent and occur earlier in patients not receiving than in those receiving prophylactic colchlcine or indomethacin. The acute attack of gout triggered by allopurinol is proposed as an "ex ingravescentibus" diagnostic criteria when the patient is seen i n an intercritical period. INTRACELLULAR PURINE AND PYRIMIDINE NUCLEOTIDE POOLS OF HUMAN T AND B LYMPHOCYTES OF DIFFERENT 203 tUTURATION STAGES. Leo J.M. Spaapen, John G.M. Scharenberg, Ben J.M. Zegers. Ger T. Rijkers, Marinus Duran, Sybe K. Wadman. University Children's Hospital. Dept. of Immunology, Utrecht, The Netherlands. It is well established that the activities of various enzymes of the purine and pyrimidine metabolic pathways vary between T and B lymphocytes And with the maturational stage of the lymphoid cells of both lineages. In the present study we investigated by HPLC analysis whether these differences are re- flected in differences in intracellular purine and pyrimidine nucleotide pools. The intracellular nucleotide pools, expressed as the ratio of total purine nucleotides over total pyrimidine nucleotides do increase with the maturational development of T and B lymphocytes: thymocytes<cord blood T cells (adult peripheral T cells; cord blood B cells <adult peripheral B cells. Moreover it was found that this ratio decreased upon mitogenic stimulation of peripheral blood T cells, whereas it increased upon mitogenic stimulation of B cells. These data should be useful as reference levels e.g. in the interpretation of purine/ pyrimidine nucleotide pool ratio's of leukaemic cells representing different stages of lymphocyte development. 204 STEADY-STATE KINETICS OF THE REACTION CATALYZED BY GMP REDUCTASE. A. Spadaro, A. Giacomello, C. Salerno Institutes of Rheumatology and Biological Chemistry, University of.Rome, and C.N.R. Centre for Melocular Biology, Rome, Italy. GMP reductase (EC 1.6.6.8) has been purified from human erythrocytes. The steady-state kinetics of the reaction catalyzed by GMP reductase are consistent with a model in which substrates bind the enzyme in an ordered sequence, first GMP and then NADPH. NADP is released from the enzyme-substrate complex by a Theorell-Chance mechanism. Ammonia and IMP are then sequentially liberated in an ordered fashion. Dead- end complexes between the enzyme and ammonia have been observed. GTP (10-200 uM) increases the apparent second-order rate constant for GMP binding and thus decreases the inhibition constant of this substrate. Neither Vmax nor Km for NADPH are affected by GTP up to 200 uM.