ADRENOMEDULLIN REGULATION BY THYROID-HORMONE IN THE RAT

To investigate the effect of thyroid hormone on adrenomedullin (AM) ch anges during hyper- and hypothyroid states, we evaluated plasma AM con centrations and AM mRNA levels in lung tissue from hyper- and hypothyr oid rats. AM peptide concentrations were significantly higher in plasm a from hyperthyroid rats and lower in plasma from hypothyroid rats com pared with control rats. AM mRNA transcripts were significantly increa sed in lung tissue from hyperthyroid rats and significantly decreased in lung tissue from hypothyroid rats compared with normal rats. These changes are paralleled alterations in AM production in cultured rat va scular smooth muscle cells, in which AM is regulated at the transcript ional level by thyroid hormone. Thus, thyroid hormone positively regul ates AM production in vivo. (C) 1998 Elsevier Science Inc.