[Hepatic dysfunction in myoglobinuric acute renal failure (rhabdomyolysis)--experimental study in rats]. / Lesão hepática na insuficiência renal mioglobinúrica (rabdomiólise)--estudo experimental em ratos.

Liver damage as a consequence of rhabdomyolysis (RM) has not been well established on clinical and experimental grounds. Hepatic dysfunction was then investigated in rats 24 h after induction of acute renal failure with glycerol. Forty male Wistar rats (220-270 g) were dehydrated for 24 h and were divided in two group: GI experimental group (n = 14)-50% glycerol was injected (10 ml/Kg, one-half of the dose in each hindlimb muscle) and GII control group (n = 26)-animals received injection of saline solution. Twenty-four hours after the glycerol or saline injection all the animals were killed. Serum urea, creatinine, transaminases (AST, ALT) and CK were measured and significantly high values were obtained in experimental animals. Arterial blood pressure was measured and remained within normal levels in both groups. Hepatocyte mitochondrial respiratory function was estimated polarographically with determination of oxygen consumption without ADP (Basal respiration-State 4) and in the presence of ADP (Activated respiration-State 3). In experimental group (GI) there was significant low values of oxygen consumption in state 3, decrease of respiratory control rate and in ADP/O ratio (p < 0.05). Histological studies of the liver revealed a periportal necrosis and centrilobular degeneration. These studies suggested that hepatic dysfunction is an additional complication of glycerol-induced rhabdomyolysis. The pathogenesis and clinical implications of these abnormalities are discussed.

Estrogens modulate the circadian rhythm of hypothalamic beta-endorphin contents in female rats.

The aim of the present study was to evaluate the changes in the diurnal rhythm of the hypothalamic beta-endorphin (beta-EP) contents in female rats as a function of circulating estrogens. With this purpose we evaluated the diurnal hypothalamic beta-EP changes (1) during the estrous cycle, and (2) in ovariectomized rats with and without acute and chronic estrogen replacement. Ovariectomized rats were treated either acutely with 10 micrograms of estradiol benzoate (EB) or chronically with 2 micrograms/day of EB for 15 days. beta-EP concentrations were measured in acid extracts of medial basal hypothalamus by a specific radioimmunoassay. During the estrous cycle, hypothalamic beta-EP concentrations showed a significant nocturnal increase, with no difference between the 4 days of the cycle. On the day of estrus, beta-EP concentrations between 12.00 and 18.00 h resulted significantly lower than in the other days of the cycle. After ovariectomy, the night-related changes in hypothalamic beta-EP disappeared. The acute administration of EB induced a significant increase in hypothalamic beta-EP after 21 h (18.00 h). On the other hand, the chronic replacement restored the nocturnal peak of hypothalamic beta-EP (18.00, 21.00, 24.00 h). The present data emphasize the role of central beta-EP in regulating the reproductive functions. Moreover, the effect of estrogen in modulating the circadian changes in hypothalamic beta-EP supports the important role of estrogens in brain function.

Norgestimate increases pituitary and hypothalamic concentrations of immunoreactive beta-endorphin.

Progesterone is a potent hormone acting on the female reproductive tract and influencing a series of other functions. Recent studies revealed a correlation between progesterone and brain neurotransmitters and neuropeptides. Our study evaluated the possible effect of norgestimate, a new progestin, on hypothalamic and pituitary beta-endorphin (B-EP) concentration in castrated female rats. Ovariectomy was performed under ethyl ether anesthesia. Treatment was started 3 weeks after surgery. Norgestimate, estradiol benzoate or norgestimate plus estradiol benzoate were administered. The two steroids were dissolved in sesame oil and injected (s.c.) every day for 2 weeks. Pituitary and hypothalamus B-EP concentrations were measured by radioimmunoassay. Our studies showed that norgestimate increases the pituitary and hypothalamic B-EP concentration in female rats, reaching values higher than controls and estrogen-treated rats. Because B-EP has an important role in reproductive function, both modulating gonadotropin secretion and sexual behavior, the present results lead to the hypothesis that norgestimate affecting B-EP concentrations may influence central functions.