Preservation of bioprosthetic valves may play a role in valvularcalcification. Subcutaneous implants in rats were used to test the effectof different preservation solutions. Fifty male Sprague-Dawley rats weredivided into five groups. Fresh bovine pericardium was treated in one offive ways: group A: 99.5% glycerol for 1 week; group B: as group A, thennormal saline wash and 0.25% formaldehyde storage for 24 h; group C: asgroup A, then normal saline wash and 4% formaldehyde storage for 24 h;group D: as group A, then normal saline wash and 0.625% glutaraldehydestorage for 24 h; group E: 0.625% glutaraldehyde and 4% bufferedformaldehyde storage. Treated bovine pericardium was cut into 1-cm2 piecesand washed for 30 min with normal saline before implantation. In eachanimal, three pieces were implanted in the subcutaneous tissue of the back.After 70 days, retrieved specimens were examined grossly, and X-raydensitometry, calcium analysis, and histological examinations were carriedout. The results showed that glycerol-treated tissue (group A) had lesscalcification (calcium 6.92 +/- 4.46 micrograms/mg dry weight) than othergroups: group B (calcium 323.12 + 63.56 micrograms/mg dry weight); group C(calcium 240.65 + 13.47 micrograms/mg dry weight); group D (calcium 232.29+ 13.01 micrograms/mg dry weight). These differences were markedlysignificant (p less than 0.0001). It appears that aldehydes play animportant role in the calcification of bioprosthetic valves. Experiencewith glutaraldehyde- and glycerol-treated pericardium in valvularapplications in sheep support these observations.