Precocious induction of pepsinogen in the stomach of suckling mice by hormones.

Effects of hormones on pepsinogen activity in mouse stomach were investigated by enzyme assay and electron microscopy. Administration of hydrocortisone alone to mice on days 5--10 increased the enzyme activity in the stomach to as much as 4.5-fold that of untreated mice and the increase was dose dependent. Thyroxine also evoked precocious differentiation of the stomach. The effects of thyroxine and hydrocortisone were additive. Injections of insulin had little effect when given alone, or in combination with other hormones. Injection of hydrocortisone alone or plus thyroxine also caused morphological differentiation of the chief cells in the stomach mucosa. Administration of thyroxine to mice on days 15--20 induced as much enzyme activity as that induced by hydrocortisone, but neither of these hormones had any effect when injected after day 23. These results suggest that besides hydrocortisone, thyroxine is also involved in differentiation of the stomach in mice for the first 20 days after birth and that the normal increase of pepsinogen activity in the stomach of mice during the late suckling period is brought about by serum glucocorticoids, possibly with thyroxine.