DISTINCT REGULATION OF 2 HYDROXYSTEROID SULFOTRANSFERASES, ST2A1 AND ST2A2, BY GROWTH-HORMONE - A UNIQUE TYPE OF GROWTH-HORMONE REGULATION IN RATS

In the present study, changes in the mRNAs of two major forms of hydro xysteroid sulfotransferases (STs), ST2A1 and ST2A2, have been determin ed in different growth hormone (GH) states, Hepatic ST2A1 mRNA was det ected in both sexes of mature Sprague-Dawley rats. The level was 5 tim es higher in the females than in the males. ST2A1 mRNA was undetectabl e in GH-deficient animals, such as hypophysectomized rats and spontane ous dwarf rats. Continuous infusion of GH (mimicking the female secret ory pattern) increased hepatic levels of ST2A1 mRNA in both GH-deficie nt animals. ST2A2 mRNA was detected only in the livers of mature femal e rats and in both sexes of GH-deficient animals, Intermittent injecti on of GH (mimicking male secretory pattern) strongly suppressed hepati c levels of ST2A2 mRNA in both GH-deficient animals. These results ind icate that pituitary GH independently regulates both ST2A1 and ST2A2 a t the pretranslational levels, These differences in GH responses betwe en ST2A1 and ST2A2 are in good agreement with their female-dominant an d female-specific modes of expression in normal rats, Furthermore, the present study demonstrates a unique response of ST2A2 to the secretor y pattern of GH among the drug-metabolizing enzymes in rat livers, in which ST2A2 mRNA levels are suppressed by the male secretory pattern b ut not by the female secretory pattern of GH.