Interaction of Glucocorticoid and Thyroxine in the Responses of Rats to Starvation-Refeeding

The interaction of glucocorticoid (GC) and thyroxine (T4) in the generation of the hepatic enzyme overshoot and lipid response to starvation-refeeding was studied. Male Sprague-Dawley rats were either left intact, or treated with propylthiouracil (PTU), or adrenalectomized (ADX), or ADX and/or PTU treated and treated with GC and/or T4. One-half of each of these treatment groups was fed a 65% glucose diet while the remaining rats were starved for 48 hours and refed the glucose diet for 48 hours. After decapitation, hepatic lipid and glucose-6-phosphate dehydrogenase (G6PD) activity were determined. Rats treated with only PTU had less of an enzyme overshoot than nontreated rats, and the full overshoot response was restored with T4 treatment. ADX rats did not have the typical enzyme overshoot response to starvation-refeeding. However, ADX rats had their overshoot response restored with GC. PTU-treated ADX rats had more of an overshoot response than did ADX rats. When T4 was administered to PTU-treated ADX rats there was less of an enzyme overshoot; however, when both T4 and GC were administered to the PTU-treated ADX rats, the overshoot response was fully restored. The liver lipid response to starvation-refeeding followed a similar pattern except that in PTU-treated rats the liver lipid levels were significantly higher in the starved-refed rats than in the ad libitum-fed rats. These results indicate that T4 and GC play a role in the G6PD and liver lipid response to starvation-refeeding.