Lactate production by thrombin-activated platelets of patients with primary thrombocythemia.

INTRODUCTION: Platelet activation needs a high energy demand which is supplied by the degradation of glucose into lactate. Platelet response to agonists in patients with primary thrombocythemia is defective. We studied the production of lactate by the platelets of patients with this disease and defective platelet aggregation. MATERIAL AND METHODS: Ten patients suffering from primary thrombocythemia and ten controls were included in this study. The lactate generation was measured in resting and thrombin activated platelets in absence or presence of glucose. RESULTS: Resting platelets incubated for 30 min in phosphate-buffered saline (PBS) generated the same amount of lactate in patients (44.6+/-21.6 micromol/10(11) cells) and controls (41.0+/-17.3 micromol/10(11) cells). Addition of glucose led to similar increases in lactate formation by platelets in patients (82.2+/-26.4 micromol/10(11) cells) and controls (88.1+/-34.5 micromol/10(11) cells). The addition of thrombin in absence of glucose did not modify the lactate formation respective to PBS. Finally, the incubation of platelets with both glucose and thrombin caused further increases in the generation of lactate in both groups, patients (236.9+/-83.9 micromol/10(11) cells) and controls (228.6+/-63.5 micromol/10(11) cells) without differences between them. The production of lactate in both groups was also similar when platelets were incubated for 10 min or 20 min with both thrombin and glucose. However at 5 min, platelets of patients generated more lactate (97.8+/-23.7 micromol/10(11) cells) than controls (66.5+/-38.7 micromol/10(11) cells, p<0.05). CONCLUSIONS: These results suggest that thrombin is able to induce an initial hyperactivity of those pathways involved in the platelet energy production of patients with primary thrombocythemia.

Hyperammonaemia as a cause of psychosis in an adolescent.

UNLABELLED: Diseases that cause hyperammonaemia usually appear during the neonatal period or during the first months of life as severe neurological metabolic distress. In some cases, as the one reported here, the age of onset and initial symptoms are non-specific and the episodes of acute metabolic encephalopathy may be attributed to encephalitis, poisoning or psychiatric problems. Our patient had N-acetyl glutamate synthetase deficiency due to a lack of activation by L-arginine. Treatment with N-carbamylglutamate was successful in maintaining normal ammonia levels. CONCLUSION: We emphasise the importance of measuring ammonia levels in patients with neurological or psychiatric symptoms as part of their diagnostic work-up.