Cortisone and thyroxine modulate intestinal lactase and sucrase mRNA levels and activities in the suckling rat.

Glucocorticoids and thyroxine modulate postnatal intestinal sucrase and lactase activities. Whether changes in enzyme activity are accompanied by changes in enzyme mRNA levels were determined in day 6 rats given thyroxine, cortisone, or thyroxine plus cortisone and killed 3 days later. Cortisone induced precocious expression of jejunal sucrase activity which was enhanced when cortisone plus thyroxine was administered; sucrase mRNA changed in parallel. Jejunal lactase activity was unaffected by thyroxine and was increased after cortisone, but not after thyroxine plus cortisone. Jejunal lactase mRNA levels increased equally after cortisone or after cortisone plus thyroxine. Thus, cortisone induces coordinated increases in sucrase and lactase activities and in corresponding mRNA levels. Thyroxine only enhances cortisone induced sucrase expression and antagonizes cortisone by depressing lactase activity post-translationally.