Epidermal growth factor and prolactin in rat anterior pituitary after chronic treatment with estradiol and triiodothyronine.

: Adult male rats were treated for 20 days either with estradiol benzoate (EB; 10 mg/kg twice a week i.m.) or triiodothyronine (T3; approx. 500 micrograms/kg daily mixed to the food) or both and the concentration of epidermal growth factor (EGF) and prolactin (PRL) in the anterior pituitary (AP) was estimated. In a preliminary experiment no difference in EGF content in the AP of male and female rats was found. The administration of EB was followed by highly significant increase in AP weight and a significant decrease in EGF content per mg of the AP, but not per whole AP. The concentration of rPRL was significantly increased in AP and serum of EB treated animals. After T3 treatment the mean concentration of EGF in the AP was slightly elevated as compared with controls. The administration of T3 together with EB prevented the increase of AP weight as observed after EB alone. However, the content of EGF as expressed per mg of the AP was not different from that in control group, though it was elevated when expressed per whole gland.