Table 1.
Deiodinase enzyme activities in growth plate tissue extracts and chondrocytes
| ATDC5 2, 7, 14, 21 day extracts and intact cells n = 4 in duplicate | Growth plate tissue 3, 6, 12 week rat extracts 6–12 rats/age/experiment n = 2 in duplicate | 1° chondrocytes 3 week rat extracts 12 rat s/experiment n = 2 in duplicate | 1° chondrocytes 6, 12 week rat extracts 6 rats/age/experiment n = 2 in duplicate | |
|---|---|---|---|---|
| D1 (fmol/min/mg) | 0 | 0 | N/D | N/D |
| D2 (fmol/min/mg) | 0 | 0 | 0 | 0 |
| D3 (fmol/min/mg) | ||||
| Con | 0 | 0 | 2.9 | 0 |
| Dex 1 μM | 0 | 0 | 1.2 | 0 |
| T3 100 nM | 0 | 0 | 0.6 | 0 |
| T4 100 nM | 0 | 0 | 1.9 | 0 |
| cAMP 1 mM | 0 | 0 | 4.6 | 0 |
| TPA 0.1 μM | 0 | 0 | 4.3 | 0 |
D1 enzyme activities were not determined in samples from primary chondrocytes because of limiting amounts of cell extract. Positive control adult human liver extracts deiodinated 100% of substrate in each 120 min D1 assay; COS-1 cell extracts transfected with human D2 possessed 12.06 fmol/min/mg D2 activity; ECC1 cell and human fetal liver extracts possessed D3 activities of 9.83 and 208 fmol/min/mg, respectively.