PLACENTAL IODOTHYRONINE DEIODINASE-III AND DEIODINASE-II RATIOS, MESSENGER-RNA EXPRESSION COMPARED TO ENZYME-ACTIVITY

Iodothyronine deiodinases In and II (D3 and D2) specific enzyme activi ties in human placenta both decrease with gestational age. The relatio n of the enzyme activities with their respective mRNA expression was i nvestigated by semi-quantitative RT-PCR on human placenta mRNA. To inv estigate if RT-PCR is a useful tool to detect iodothyronine deiodinase mRNA, several tissues were screened using this technique. In all tiss ues with iodothyronine deiodinase enzyme activity, the corresponding R T-PCR product is present. Similar to D3 specific enzyme activity, the amount of D3 mRNA in placenta declines with gestational age. The ratio s of the D3/D2 enzyme activity and mRNA. expression in placenta do not correlate. D3 enzyme activity shows an average 300-fold excess compar ed to D2 activity. However, semi-quantitative PCR analysis of D3 and D 2 mRNA shows a D3/D2 ratio varying from 0.05 to 52. These results sugg est that the placental D2 mRNA amplified is not translated into placen tal D2 enzyme activity. (C) 1998 Elsevier Science Ireland Ltd. All rig hts reserved.