The effect of hypophysectomy on the uterine response to estradiol

Following estradiol (E₂) administration early increases (within 4 h) in uterine wet weight and the synthesis of 2-deoxyglucose-6-phosphate (2-DGP) from 2-deoxyglucose (2-DG) are similar in ovariectomized (OVX) and ovariectomizedhypophysectomized (OVX-HX) rats. Most late uterine responses occurring 24 h after hormone treatment, however, are greatly diminished in OVXHX animals relative to OVX animals. The diminished responses include increases in uterine wet weight, dry weight, RNA content, protein content and the incorporation of thymidine into uterine DNA. These late uterine responses are not diminished in OVXSham HX rats relative to OVX rats. The diminished responses observed in OVX-HX rats are not due to a shift in the dose-response curve for E₂, but result from a decrease in the magnitude of the maximum uterine response. These diminished responses are not due to alterations in the content, structure or binding affinity of uterine E₂ receptors in OVX-HX rats relative to OVX rats. One late response, the synthesis of 2-DGP from 2-DG 24 h after E2 treatment, is not significantly diminished in OVX-HX rats. These results suggest that a pituitary factor(s) is directly or indirectly required for the complete uterine response to E₂ to occur normally in OVX rats.