Reversal of impaired calcium homeostasis in the rat diaphragm subjected toMonocrotaline-induced pulmonary hypertension

Monocrotaline (MCT) pneumotoxicity is known to alter the structure of pulmo nary vascular wall and impairs endothelial cell function resulting in pulmo nary hypertension. Its effect on the diaphragm muscle has not yet been eluc idated. This study examines the effect of MCT pneumotoxicity on calcium tra nsport in the rat diaphragm. Pulmonary hypertension induced by MCT pneumoto xicity caused a significant increase (P<0.001) in calcium accumulation in s trips isolated from rat diaphragms. Treatment of rats having received MCT w ith Indapamide reduced calcium uptake by diaphragmatic strips to levels tha t are not significantly different from the control (P > 0.05). Treatment wi th Indapamide alone did not elicit any change in calcium accumulation in th e diaphragmatic strips. Treatment of the animals with MCT, Indapamide or bo th did not produce any significant change (P > 0.05) in the cell volume of the diaphragmatic strips. Pulmonary hypertension increased calcium uptake b y the muscle cells in the rat diaphragm which may alter diaphragmatic contr actility; an effect that was prevented by Indapamide. (C) 1999 Elsevier Sci ence Ireland Ltd. All rights reserved.