Effects of orchidectomy and hormone replacement on rat hepatic hexose monophosphate pathway enzymes
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abstract
This study was designed to determine if the attenuated starvation-refeed (SRF) over shoot response of hepatic G6PDH and 6PGDH observed in adult female rats is due to the presence of high levels of estrogen or lower levels of testosterone in the female. Male rats were castrated as weanlings, then allowed to reach adulthood before initiation of the remainder of the study. Ten days prior to the dietary study, when the rats were 9 weeks old, they began to receive daily injections of one of the following preparations: carrier only, 17--estradiol or testosterone propionate. Next, the rats were starved for 2 days and refed either a nonpurified diet or a purified 65% carbohydrate diet (sucrose, fructose, glucose or cornstarch) for 3 days. Castration suppressed the magnitude of the SRF overshoot response by 40% compared to that observed in intact males. Testosterone injections did not restore the SRF response. In fact, the enzyme activities of testosterone- injected, castrated rats were indistinguishable from those of castrated, carrier-injected controls. Estrogen injections doubled basal G6PDH and 6PGDH activities, but decreased the SRF overshoot response by 60% compared to castrated carrier injected rats. These results suggest that estrogen promotes higher basal enzyme activities and suppresses the magnitude of the SRF overshoot response in adult female rats.
