Nifedipine-mediated mobilization of intracellular calcium stores increases spontaneous neurotransmitter release at neonatal rat motor nerve terminals.

The modulation of spontaneous release of acetylcholine by specific Ca2+ channel blockers was studied at neonatal rat neuromuscular junction. During early postnatal periods (0-4 days), blockers of N- and P/Q-type Ca2+ channels did not affect miniature endplate potential (MEPP) frequency. Unexpectedly, treatment with the L-type Ca2+ channel antagonist nifedipine, although not when treated with isradipine, nitrendipine, or calciseptine, resulted in strong increase in MEPP frequency. The potentiation effect of nifedipine was dose-dependent with a 56-fold maximum effect with 15 microM. The effect decreased during the first two postnatal weeks and disappeared by the third. The effect of nifedipine was not dependent on extracellular Ca2+ and was not altered by the presence of other Ca2+ channel blockers. In contrast, it was abolished by depleting intracellular Ca2+ stores with 2 microM thapsigargin and was partially inhibited by 10 microM ryanodine. In conclusion, we report a new ryanodine receptor-mediated effect of nifedipine on neonatal neuromuscular junction that may indicate the developmental expression of a specific receptor channel that interacts with intracellular Ca2+ stores. This effect of nifedipine should also be considered when using this drug as either a therapeutic or a research tool.

[Bronchiolitis obliterans with organizing pneumonia associated with idiopathic thrombocytopenic purpura]. / Bronquiolitis obliterante con neumonía organizada asociada a púrpura trombocitopénica idiopática.

We report a case of a 35 year-old woman with idiopathic thrombocytopenic purpura (ITP) who, under treatment with immunosuppressive drugs, developed bilateral interstitial pulmonary disease. Previously she had been splenectomized and treated with corticosteroids and cyclosporin. During the clinical course, the patient developed alterations of the hepatogram and presented a positive serology for Epstein-Barr virus. The lung biopsy showed the histologic pattern of obliterative bronchiolitis, interstitial inflammatory infiltration and intraalveolar pneumonia (BOOP). We could not find in the literature a previous report in which ITP was associated with BOOP. Of interest was the spontaneous remission of the pulmonary disease after suppression of cyclosporin and positive serology for Epstein-Barr virus.