Alterations in plasma prolactin and glucose levels induced by surgical stress in hyperprolactinemic female rats.

The effects of hyperprolactinemia on plasma prolactin (PRL) and glucose were investigated in female rats submitted to surgical stress (laparotomy under ether anesthesia). Wistar rats weighing 250-280 g received pituitary grafts under the kidney capsule three weeks before the experiments (N = 15) while a control group underwent sham transplantation (N = 14). The sham-operated rats presented a three-fold increase of PRL levels as early as after 5 min of surgical stress (P < 0.01); the PRL levels reached a peak at about 15 min and returned to baseline at 40 min. The PRL levels of the grafted rats were increased 3.5-fold compared to the sham-operated controls before stress (20.2 +/- 5.6 ng/ml vs 5.8 +/- 0.9 ng/ml, respectively; P < 0.05), but did not change significantly during the experimental period. Plasma glucose was already significantly increased at 5 min in sham-operated control and grafted rats (P < 0.01) and reached maximal concentrations at about 15 min. The grafted rats presented higher glucose levels than sham-operated controls before stress (122.2 +/- 3.3 vs 100.5 +/- 4.2 mg/dl; P < 0.01) and at 40 min (182.6 +/- 13.6 vs 146.7 +/- 8.4 mg/dl; P < 0.05). The hyperprolactinemic rats showed impaired surgical stress-induced PRL release and higher glucose levels both at rest and during the first postoperative hour. These results indicate that chronic hyperprolactinemia inhibited PRL secretion and enhanced the hyperglycemic stress response in the female rat.