An annual shrub, found in the southern United States as a cover crop, called Crotalaria spectabilis, bears stems, foliage, and seeds containing the pyrrolizidine alkaloid monocrotaline which produces experimental pulmonary hypertension. A diet of C spectabilis seeds leads to pulmonary hypertension with medial hypertrophy of small pulmonary arteries, right ventricular hypertrophy, and congestive heart failure with organ congestion in young rats. Evidence of pulmonary hypertension includes direct measurements of right atrial and ventricular pressures.
Through a series of fascinating experiments, the authors put together a chain of evidence with a skill which parallels the sequential arguments of a trial lawyer. The evidence that C spectabilis induces pulmonary hypertension is generously convincing. The mechanism is not known and probably is not due to mast cell increase which occurs paralleling the exudative pulmonary changes and seems to have nothing to do with serotonin, although the hypothesis was attractive. Although this is a