Thyroid hormone modulation of rat sulphotransferase mRNA expression

Abstract

1. Thyroid hormones modulate sulphotransferase (SULT) enzyme expression. Specific substrates are not available for the study of the SULT isoforms, so the regulation of hepatic SULT mRNA expression by thyroid hormones was examined by Northern blot analysis with oligonucleotide probes specific for each SULT mRNA, including maledominant phenol SULT(1A1,1C1,1E2), female-dominant hydroxysteroidSULT(20} 21, 40} 41, 60), and a non-sex-dependent SULT, 1B1. The male and female rat were either untreated, thyroidectomized (TX), or TX and given thyroid hormones (thyroxine [T₄, 20 μg kg⁻¹ day⁻¹] and 3,5,3′-triiodothyronine [T₃, 5 μg kg⁻¹ day ⁻¹]). 2. With regard to phenol SULTs, expression of SULT1A1 or SULT1B1 mRNA was not altered in either sex by TX. TX increased SULT1E2 mRNA expression 3-fold in the male and 2.5-fold in the female rat. The increase in SULT1E2 mRNA was partially reversed by infusion of T₃/T₄ in the male, and was not reversed in the female. 3. With regard to hydroxysteroid SULTs, TX decreased expression of SULT20/21 mRNA in the male rat by 70 and 60% in the female, and these decreases were reversed by T₃/T₄ infusion. SULT40/41 mRNA expression increased in the male rat 3-fold and decreased in the female TX rat by 25%. SULT60 mRNA expression increased 3-fold by TX in the female rats.The effects of TX on SULT40/41 and SULT60 mRNA expression were reversed by infusion of T₃/T₄. 5. Thus, phenol sulphotransferases were not markedly affected by thyroid hormones except for SULT1E2, but each hydroxysteroid sulphotransferase isoform was affected by thyroidectomy. Therefore, thyroid hormones regulate SULT gene expression in an isoform-specific manner.