The effect of ovarian hormones on antioxidant enzyme activities in the brain of male rats

The brain is widely responsive to gonadal hormones. The functional significance of ovarian hormones in the brain is evident from biochemical studies indicating that estradiol or progesterone treatment of testectomized rats produces changes of antioxidant enzyme activities. The effect of estradiol benzoate (EB) and progesterone (P) in the control of antioxidant (AO) enzyme activities was studied in the brain of adult male Wistar rats. The activities of catalase (CAT), glutathione peroxidase (GSH-Px), glutathione-S-transferase (GST) and glutathione reductase (GR) were measured in appropriate subcellular fractions, prepared from brains of animals belonging to various experimental groups. These groups were designed with the intention to follow changes in enzyme activities 2 h or 24 h after systemic administration of 5 microg EB or 2 mg P to testectomized (TX) animals. The obtained results show that both EB and P increase CAT activity, whereas EB decreases GSH-Px, GST and GR activities. These findings clearly show the modulatory role of EB and P in the control of enzymes responsible for the protection of rat nerve cells against oxidative damage caused by free oxygen radicals.     

Effects of estradiol benzoate and progesterone on superoxide dismutase activity in the thymus of rats

The activity of mitochondrial superoxide dismutase (MnSOD) and cytosol superoxide dismutase (CuZnSOD) was measured in corresponding subcellular fractions prepared from the thymi of intact and chronically gonadectomized (GX) rats of both sexes, as well as of GX male and female rats injected subcutaneously with a single dose of 5 microg estradiol benzoate (EB) and/or 2 mg progesterone (P). Animals were sacrificed 2 h or 24 h following hormone treatment. In the females, the activity of MnSOD in the thymus was stable during the estrous cycle and did not change after ovariectomy. Treatment of GX females with estradiol benzoate resulted 2 h later in a significant elevation of MnSOD activity, whereas 24 h later the activity returned back to control values. On the other hand, treatment of GX females with progesterone had no effect on the MnSOD activity. However, combined hormone treatment, in which EB injection preceded progesterone injection by one hour, enhanced the effect on MnSOD activity similar to that of estradiol benzoate alone. The activity of CuZnSOD in cycling rats was increased in proestrus, whereas removal of the ovaries kept the values at low diestrus and estrus levels. Contrary to MnSOD, CuZnSOD activity did not change after EB treatment of GX females, while progesterone increased the enzyme activity at 2 h and 24 h after hormone treatment. However, combined EB+P treatment proved to be ineffective. In the males, neither MnSOD nor CuZnSOD activity was affected by the removal of testes or by progesterone treatment of GX animals. Only EB injection to GX rats significantly increased CuZnSOD activity 24 h later.     

Antioxidant enzymes in the liver of Chelidonichthys obscurus from the Montenegrin coastline

The activities of antioxidant defence enzymes — total, manganese and copper zinc containing superoxide dismutase (Tot SOD, Mn SOD, CuZn SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR) and biotransformation phase II enzyme glutathione-S-transferase (GST) — in the liver of longfin gurnard (Chelidonichthys obscurus) from the Montenegrin coastline (Adriatic sea) were investigated. The specimens were collected in winter (February) and late spring (May) at two localities: Platamuni (PL, potentially unpolluted) and the Estuary of the River Bojana (EB, potentially polluted). The obtained results show that the activities of Mn SOD, CAT, GSH-Px and GST in winter were significantly lower at EB than at PL. In spring, the activities of CAT and GST were decreased, while GR activity was increased at EB in comparison to PL. The activities of Mn SOD and GST at PL were decreased and GSH-Px, GR and GST activities at EB were increased in spring compared to winter. Our work represents the first study of liver antioxidant enzymes of longfin gurnard from the Montenegrin coastline and reveals that locality, as a variable, has a greater influence on antioxidant enzymes and biotransformation phase II enzyme GST activities compared to season.     

Inhibition of Estrogen-Induced Sexual Receptivity by Androgens: Role of the Androgen Receptor

Both naturally occurring and synthetic androgens have been shown to inhibit estrogen-induced sexual receptivity when administered to ovariectomized (OVX) rats. The mechanisms by which androgens exert these effects, however, remain unclear. Experiments were conducted to determine the role of the androgen receptor in the inhibition of estrogen-induced sexual receptivity in OVX rats by using flutamide, an androgen receptor antagonist. In each experiment, OVX Long–Evans rats received 6 consecutive days of estradiol benzoate (EB; 2.0 μg/day) followed by 15 days of EB concurrent with flutamide (10.0 mg/kg; twice daily) or the vehicle and one of the following androgens or the vehicle: dihydrotestosterone propionate (7.5 mg/kg), 3α-androstanediol (3.75 mg/kg), 17α-methyltestosterone (7.5 mg/kg), stanozolol (7.5 mg/kg), or nandrolone decanoate (7.5 mg/kg). On Day 15, all female rats received progesterone (P; 1.0 mg/rat) 4 h before testing. Tests for sexual receptivity were conducted on Days 3, 6, 14, and 15 of androgen/flutamide treatment. Each androgen inhibited sexual receptivity as expected, and concurrent treatment with flutamide reversed the inhibitory effects of all androgens on sexual receptivity on all test days. High levels of sexual receptivity were displayed in response to P on Day 15, regardless of experimental treatment. These results suggest that naturally occurring and synthetic androgens act at the androgen receptor to inhibit estrogen-induced sexual receptivity in OVX rats.     

NGF restores decrease in catalase activity and increases superoxide dismutase and glutathione peroxidase activity in the brain of aged rats.

The effects of ageing on the activity of copper-zinc superoxide dismutase (SOD), selenium-dependent and independent glutathione peroxidase (GSH-Px) and catalase in several areas of the brain in 3-, 12-, and 24-month-old rats were studied. In addition, the effects of a subacute intracerebroventricular treatment of NGF (1 microgram daily for 28 consecutive days) on SOD, GSH-Px, and catalase activity in the same areas of the brain were assessed. The effects of ageing on the activities of antioxidant enzymes varied considerably in the different brain areas studied. Copper-zinc SOD was alone in being unaffected by ageing. Intraventricular infusion of NGF significantly increased SOD activity in the prefrontal cortex, hypothalamus, caudate nucleus, and mesencephalon of 24-month-old rats. Selenium-dependent GSH-Px activity did not significantly change in 12-month-old rats but it increased in the lower brain stem of 24-month-old animals. In comparison to vehicle-treated rats, NGF significantly increased selenium-dependent GSH-Px activity in all brain areas studied in 12- and 24-month-old rats. Catalase activity decreased significantly in the majority of the brain areas studied in 12- and 24-month-old rats. NGF completely restored the fall in catalase activity in 12- and 24-month-old animals to levels similar to those occurring in young rats. In conclusion, the present experiments show, for the first time, that long-term intraventricular administration of NGF significantly increases in old animals the activity of key enzymes involved in the metabolic degradation of superoxide radicals and hydrogen peroxide.     

Reversal of progesterone-induced sequential inhibition by progesterone metabolites

Previous reports have shown that intrabrain administration of progesterone (P) ring A-reduced metabolites into the medial preoptic area (MPOA) and ventromedial hypothalamus (VMH) induces facilitation of female sexual behaviour in ovariectomized (ovx) rats pretreated with estrogen. Present studies were designed to explore the possibility that ring-A reduced progesterone metabolites might play a role in controlling the duration of estrous behavior. To this aim ovariectomized (ovx) Sprague Dawley rats implanted with guide cannulae directed towards the VMH or the MPOA were submitted to a systemic hormonal treatment to provoke P-induced sequential inhibition (estradiol benzoate (EB) at time 0 + P at 44 h + P at 68 h). The second dose of P was administered simultaneously with the ic implantation of one of the following P metabolites: 3β-hydroxy-5β-pregnan-20-one (5β,3α P), 3α-hydroxy-5β-pregnan-20-one (5β,3α P) or 3β-hydroxy-5βpregnan-20-one (5α,3β P) into the MPOA or VHM. Lordosis behavior was evaluated by the lordosis quotient (LQ = number of lordosis/10 male mount × 100) and by the percentage of responding subjects. Results show that 5β,3βP implanted into the VMH or MPOA counteracted the sequential inhibitory effect induced by systemic administration of P. 5α,3β P was also able to counteract sequential inhibition, but with less potency and only in the VMFI. Results show that P-induced sequential inhibition can be counteracted by intrabrain administration of ring-A reduced progestins in both the VMH and MPOA. Data are discussed in terms of a putative physiological role of naturally occurring P metabolites in P-mediated female sexual behavior expression.     

Estrogen (EB) and EB + progesterone (P) induced changes in pituitary sodium, potassium adenosine triphosphatase activity (ATPase).

Estradiol-benzoate (EB) injected into previously ovariectomized (OVX) rats, increased pituitary ATPase activity 69% over controls, within one hour of treatment. Twelve hours after injection, ATPase activity was not significantly different from controls. Progesterone [(P): 5mg/100gBW] administered in conjunction with EB elicited an analogous response. AT at time of EB and EB+P induced increments in pituitary ATPase activity, plasma LH levels were dramatically reduced to normal, intact diestrous control levels. Post-castrational elevations in FSH were also suppressed after one hour of treatment with EB, but not following EB+P administration. The results suggest that the inhibitory actions of EB and EB+P on post-castrational LH levels may be related to modulation by these steroids of pituitary membrane ATPase activity.     

Mu-, delta-, and kappa-opioid receptor agonists selectively modulate sexual behaviors in the female rat: differential dependence on progesterone.

Previous studies suggested that opioid receptor agonists infused into the lateral ventricles can inhibit (through mu receptors) or facilitate (through delta receptors) the lordosis behavior of ovariectomized (OVX) rats treated with estrogen and a low dose of progesterone. The present study investigated the behavioral and hormonal specificity of those effects using more selective opioid receptor agonists. Sexually experienced OVX rats were implanted stereotaxically with guide cannulae aimed at the right lateral ventricle. One group of rats was treated with estradiol benzoate (EB, 10 micrograms) 48 hr and progesterone (P, 250 micrograms) 4 hr before testing, whereas the other group was treated with EB alone. Rats were infused with different doses of the selective mu-receptor agonist DAMGO, the selective delta-receptor agonist DPDPE, or the selective kappa-receptor agonist U50-488. The females were placed with a sexually vigorous male in a bilevel chamber (Mendelson and Gorzalka, 1987) for three tests of sexual behavior, beginning 15, 30, and 60 min after each infusion. DAMGO reduced lordosis quotients and magnitudes significantly in rats treated with EB and P, but not in rats treated with EB alone. In contrast, DPDPE and U50-488H increased lordosis quotients and magnitudes significantly in both steroid-treatment groups. Surprisingly, measures of proceptivity, rejection responses, and level changes were not affected significantly by mu or kappa agonists, although proceptivity and rejection responses were affected by DPDPE treatment. These results suggest that the effects of lateral ventricular infusions of opioid receptor agonists on the sexual behavior of female rats are relatively specific to lordosis behavior. Moreover, the facilitation of lordosis behavior by delta- or kappa-receptor agonists is independent of progesterone treatment, whereas the inhibitory effect of mu-receptor agonists on lordosis behavior may require the presence of progesterone.     

Monosialoganglioside increases catalase activity in cerebral cortex of rats

Monosialoganglioside (GM1) is a neuroprotective agent that has been reported to scavenge free radicals generated during reperfusion and to protect receptors and enzymes from oxidative damage. However, only a few studies have attempted to investigate the effects of GM1 on enzymatic antioxidant defenses of the brain. In the present study, we evaluate the effects of the systemic administration of GM1 on the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px), and on spontaneous chemiluminescence and total radical-trapping potential (TRAP) in cerebral cortex of rats ex vivo. The effects of GM1 on CAT activity and spontaneous chemiluminescence in vitro were also determined.

Animals received two injections of GM1 (50 mg/kg, i.p.) or saline (0.85% NaCl, i.p.) spaced 24 h apart. Thirty minutes after the second injection the animals were sacrificed and enzyme activities and spontaneous chemiluminescence and TRAP were measured in cell-free homogenates. GM1 administration reduced spontaneous chemiluminescence and increased catalase activity ex vivo, but had no effect on TRAP, SOD or GSH-Px activities. GM1, at high concentrations, reduced CAT activity in vitro. We suggest that the antioxidant activity of GM1 ganglioside in the cerebral cortex may be due to an increased catalase activity.     

Effects of diosgenin on myometrial matrix metalloproteinase-2 and -9 activity and expression in ovariectomized rats

Diosgenin, a traditional Yam extraction, has been used in hormone replacement for menopausal women. We aimed to investigate the influences of diosgenin administration upon the MMP-2 and -9 activity and expression and reproductive hormones of ovariectomized (OVX) rats, a model of menopausal status. Seven-week old female Wistar rats with bilateral OVX or sham operation (controls) were divided and administered different dosages of diosgenin (0, 10, 50, or 100 mg/kg/day) for 8 weeks. Serum was then sampled for progesterone (P4) and estradiol (E2) assay and uterine horns harvested. Myometrial MMP-2 and -9 activity and expression were surveyed and myometrial collagen expression was also assayed. The results show higher body weight in OVX rats across the 8 weeks post surgery and no significant differences were noted among OVX or Sham rats with diosgenin supplements. There were lower P4 and E2 concentrations in OVX rats compared to Sham rats, and higher P4 concentration of Sham rats post diosgenin supplement. MMP-2 and -9 mRNA expression and activity was lower in OVX rats, although higher MMP-2 and lower MMP-9 activity/mRNA expression was observed in OVX rats post diosgenin supplementation. Collagen mRNA expression was higher in OVX rats compared to Sham controls, and diosgenin administration decreased collagen mRNA expression in OVX rats. In conclusion, diosgenin is associated with gelatinase expression and collagen metabolism in OVX rats. Diosgenin administration can partially reverse the effects of OVX upon MMP functions and hormone status. Adequate diosgenin supplement might modulate myometrial gelatinase expression and collagen metabolism in menopausal subjects.     

Exercise training with ageing protects against ethanol induced myocardial glutathione homeostasis

Glutathione plays a central role in the maintenance of cellular antioxidant defense. The alterations in the glutathione and associated recyclic enzymes caused by both exercise training and ethanol are well documented; however, their interactive effects with age are not well understood. Therefore, the influence of ageing and the interactive effects of exercise training and ethanol on the myocardial glutathione system in 3 months and 18 months old rats were examined. The results showed a significant (p<0.01) reduction in GSH content, Se and non-Se GSH-Px, GR and GST activities in the myocardium of rat with age. A significant increase (p<0.05) in the activities of these enzymes was observed in both age groups of rats in response to exercise training. This exercise-induced elevation of Se and non-Se GSH-Px and GR activities was more pronounced in the 18 months old rats when compared to 3 months old rats. Ethanol consumption significantly (p<0.05) reduced the GSH content, Se and non-Se GSH-Px and GR activities in both age groups of rats. In contrast, ethanol consumption significantly (p<0.05) increased the activity of GST. The combined action of exercise plus ethanol significantly (p<0.05) elevated the GSH content, Se and non-Se GSH-Px, GR and GST activities when compared to the ethanol treated rats in both age groups, indicating the suppression of ethanol-induced oxidative stress by exercise training. In conclusion, there was a compensatory myocardial response lessening ethanol-induced oxidative stress by exercise training, which seemed to result from the higher activity of glutathione recycling and utilizing enzymes, which may be critical for preventing chronic oxidative damage to the myocardium during ageing and even due to ethanol consumption.     

Influence of intracerebroventricular (ICV) injection of ACTH (1-24) on plasma gonadotropin in female rats: dose-response study

The intracerebroventricular (ICV) injection of ACTH (1-24) (0.1, 1.0 and 2.5 micrograms) to adult conscious ovariectomized (OVX) rats caused a dose-related inhibition of plasma LH at 10 min postinjection. The ICV injection of ACTH (1-24) (2.5 micrograms) to OVX rats in the absence or presence of a single dose of estradiol benzoate (OVX + EB): a) Decreased significantly plasma LH levels in OVX rats at 10 and 30 min postinjection. b) Decreased significantly plasma LH levels in (OVX + EB) rats at 10 min but not at 30 min postinjection. c) Did not change plasma FSH levels at 10 or 30 min postinjection in both (OVX) or (OVX + EB) rats. d) Did not change plasma ACTH levels at 10 or 30 min postinjection in (OVX) rats. Our observation suggest that ACTH (1-24) inhibited plasma LH, possibly through brain sites of action.     

Uterine glutathione reductase activity: modulation by estrogens and progesterone

The aim of this study was to determine whether glutathione reductase activity in uterine tissue is regulated by sex hormones. In spayed rats uterine glutathione reductase was significantly increased by exogenous estrogen (P< 0.01), progesterone (P< 0.01) or estrogen plus progesterone (P<0.01). When enzyme activity is expressed per mg protein, daily administration of estrogen or progesterone induces a progressive increase of this enzyme between 24 to 48 h or 24 to 72 h of treatment, respectively. Whereas the combination of both steroids causes an earlier and higher increase in glutathione reductase activity at 24 h of treatment. Estradiol singly or in combination with progesterone induced the highest protein concentration in the uterus. Whereas uterine DNA concentration is only significantly affected by estradiol. Our results suggest that uterine glutathione reductase is regulated by estradiol and progesterone and may be involved in maintaining levels of reduced glutathione in the uterus. This compound may be required for control of the redox state of thiol groups and in detoxification reactions involving H2O2 and electrophylic substances. The antioxidant action of estrogens is partially due to the stimulation of glutathione reductase.     

Monosialoganglioside Increases Catalase Activity in Cerebral Cortex of Rats

Monosialoganglioside (GM1) is a neuroprotective agent that has been reported to scavenge free radicals generated during reperfusion and to protect receptors and enzymes from oxidative damage. However, only a few studies have attempted to investigate the effects of GM1 on enzymatic antioxidant defenses of the brain. In the present study, we evaluate the effects of the systemic administration of GM1 on the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px), and on spontaneous chemiluminescence and total radical-trapping potential (TRAP) in cerebral cortex of rats ex vivo. The effects of GM1 on CAT activity and spontaneous chemiluminescence in vitro were also determined.

Animals received two injections of GM1 (50?mg/kg, i.p.) or saline (0.85% NaCl, i.p.) spaced 24?h apart. Thirty minutes after the second injection the animals were sacrificed and enzyme activities and spontaneous chemiluminescence and TRAP were measured in cell-free homogenates. GM1 administration reduced spontaneous chemiluminescence and increased catalase activity ex vivo, but had no effect on TRAP, SOD or GSH-Px activities. GM1, at high concentrations, reduced CAT activity in vitro. We suggest that the antioxidant activity of GM1 ganglioside in the cerebral cortex may be due to an increased catalase activity.     

Role of ovarian secretion in the development of dysfunction in the regulation of luteinizing hormone secretion in female rats exposed to constant illumination.

Female rats in constant illumination (LL) fail to show the facilitation of LH release following steroid administration that is characteristic of animals in normal lighting. To determine whether this effect is mediated through changes in ovarian function, rats were spayed either at the time of placement into different lighting schedules (LL or a 14:10 light-dark (LD) schedule) or 10 weeks later, and their plasma LH responses to steroids were compared after an additional 3-week exposure to the experimental lighting conditions. To test the LH response, estradiol benzoate (EB) was injected at 12.00 h and followed 72 h later by injection of progesterone (P) or a second injection of EB. Neither steroid regime revealed differences in LH release between animals ovariectomized at the time of placement into LL and those spayed 10 weeks later. The duration of castration in animals in LD affected the LH response to a priming dose of EB, but not to a second dose of EB or to P. It is concluded that altered ovarian activity is not the factor which mediates the loss of a facilitatory response of LH release following administration of gonadal steroids to rats under constant illumination.     

Systemic ICI 182,780 alters the display of sexual behaviors in the female rat

The present study investigates the effects of the antiestrogen ICI 182,780 (ICI) on the display of sexual behaviors in female rats. ICI 182,780 is a pure anti-estrogen and when given systemically, ICI is thought to act only in the periphery, and is not believed to cross the blood brain barrier. The present study examines the effects of ICI on sexual receptivity and on paced mating behavior following treatment with estradiol benzoate (EB) and progesterone (P) (Experiment 1) or with EB alone (Experiment 2). In Experiment 1, ICI (250.0 microg) did not affect the display of receptivity or paced mating behavior induced by EB and P. In contrast, in Experiment 2 female rats receiving EB alone displayed a decrease in the level of sexual receptivity following treatment with 500.0 and 750.0 microg ICI (but not 250.0 microg ICI). In addition, in Experiment 2 EB-treated female rats receiving 250.0 microg ICI spent more time away from the male rat following an intromission and were more likely to exit from the male compartment following a mount. Last, ICI had potent antiestrogenic effects on vaginal cytology (Experiment 2) and on the uterus (Experiments 1 and 2). The present study supports a role for peripheral estrogen receptors in sexual receptivity and paced mating behavior and suggests that estrogen receptor activation may decrease the aversive sensation associated with sexual stimulation.     

Paced mating behavior in female rats in response to different hormone priming regimens

A female rat will display a repertoire of behaviors during a sexual encounter with a male rat including sexually receptive (the lordosis response) and proceptive (hopping, darting) behaviors. In addition, when given the opportunity, a sexually receptive female rat will approach and withdraw from the male rat, controlling the timing of the receipt of mounts, intromissions, and ejaculations, a behavior known as paced mating behavior. The present experiments tested the hypotheses (1) that progesterone regulates paced mating behavior, and (2) that multiple hormone regimens used previously to induce sexual receptivity have the same effect on paced mating behavior. Paced mating behavior was assessed in sexually receptive ovariectomized female rats after treatment with: (1) estradiol benzoate (EB; 30.0 mg/kg) followed by a range of doses of progesterone (P; 1.0-8.0 mg/kg), (2) two pulses of unesterified estradiol (E2; 2.0 microg/rat) followed by 1.0 mg/rat of P, and (3) EB alone (5.0 microg/rat) for 6 days. No differences in sexual receptivity or in paced mating behavior were observed across doses of P (1.0-8.0 mg/kg). In contrast, the number of hops and darts per min increased with the dose of P administered. E2 + P administration resulted in slightly, but significantly, lower levels of sexual receptivity along with significantly longer contact-return latencies following an intromission in relation to the other treatment conditions. In addition, female rats exhibited fewer hops and darts per min in response to E2 + P than in response to EB + 8.0 mg/kg of P. The administration of EB alone for 6 days induced levels of receptivity and paced mating behavior indistinguishable from EB + P, while eliciting significantly fewer hops and darts per min than the EB + 8.0 mg/kg P treatment condition. Hormone priming regimen had no effect on the percentage of exits displayed during the paced mating tests in any experimental phase. Dose of P had no effect on paced mating behavior in sexually receptive rats. In addition, P does not appear to be necessary for the display of paced mating behavior following long-term treatment with EB. In contrast, the pulsatile administration of E2 + P induced a different pattern of paced mating behavior in sexually receptive rats.     

Differential effects of the perinatal steroid environment on three sexually dimorphic parameters of the rat brain

Gonadectomy of male rats was performed at 0, 6-7 (6h), 12-13 (12h), or 24 h postnatally in order to examine the influence of testosterone exposure on sexual differentiation of the brain. The indices examined were: the volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) and luteinizing hormone (LH) and follicle-stimulating hormone (FSH) titers following estradiol benzoate (EB) and progesterone (P) administration. Control animals were sham-operated at 0 h and gonadectomized at 29 days of age (sham). A decrease in the percentage of males with elevated plasma LH levels following P was found with increasing delay before gonadectomy. Significant (P less than 0.001) differences existed in the amplitude of plasma LH titers 5 h following P administration between sham, 0 h, and 6 h groups. Follicle-stimulating hormone was also elevated in all neonatally gonadectomized male groups following P administration, but there was no difference between the groups. Volume of the SDN-POA was significantly (P less than 0.001) smaller in all gonadectomized males when compared to that of sham-operated males, but no differences existed between males gonadectomized at the different hours postpartum. In female rats gonadectomized at 0 h (F0h), LH levels were elevated 5 h following P, but only to a magnitude of 36% of that of sham-operated controls (P less than 0.001). Volume of the SDN-POA of the F0h group was significantly reduced (P less than 0.05) when compared to that of sham females. Thus, in males, the presence of the tests prenatally may be responsible for the initiation of masculinization of LH release mechanisms and the SDN-POA, but both require further androgen exposure for their completion. In addition, the LH and FSH regulating systems show a differential sensitivity to the steroid hormone environment during development that shapes the animal's response to steroid as an adult.     

Progesterone inhibition of estrogen-induced maternal behavior in hysterectomized-ovariectomized virgin rats.

Hysterectomized-ovariectomized virgin rats were tested for maternal behavior following treatment with 100 μg/kg EB immediately at surgery and either oil, 0.5 or 5.0 mg progesterone either 0, 24 or 44 hr following surgery. Stimulus pups were presented 48 hr postoperatively which is counted as Day 0 of testing. EB + oil-treated females displayed short-latency maternal behavior beginning on Day 0. The injection of 5.0 mg progesterone at 0, 24, or 44 hr significantly inhibited the onset of maternal care while the effect of the lower dose of progesterone depended upon the timing of its administration in relation to that of EB. At a dose of 0.5 mg, progesterone given 24 hr following EB, inhibited the appearance of maternal behavior but had no effect given at 44 hr, and resulted in only a partial delay when given at the same time as the EB. Possible mechanisms by which progesterone interfered with the display of maternal behavior were discussed.     

The effects of cold acclimation and nitric oxide on antioxidative enzymes in rat pancreas

Alterations of pancreatic antioxidative defense (AD) and possible nitric oxide (NO) role in AD organization of adult rats receiving l-arginine.HCl (2.25%) or N(omega)-nitro-l-arginine methyl ester (L-NAME.HCl, 0.01%) as drinking liquids and maintained at room (22+/-1 degrees C) or low (4+/-1 degrees C) temperature for 45 days were studied. For that purpose, copper, zinc- and manganese superoxide dismutase (CuZnSOD, MnSOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione S-transferase (GST) and glutathione reductase (GR) activities were determined. Cold-induced decrease of CuZnSOD was inhibited with L-NAME, while l-arginine produced the same effect as cold in both supplemented groups. Cold acclimation elevated GSH-Px activity. l-Arginine and L-NAME expressed no effect on GSH-Px in rats kept at room temperature. L-NAME additionally elevated cold-induced GSH-Px activity, l-arginine expressing a similar trend. Cold-induced increase in GST activity was inhibited by L-NAME, while l-arginine inhibited this enzyme in both supplemented groups. Cold acclimation increased GR activity in control and L-NAME-treated group and l-arginine expressed a similar trend. Neither of the treatments affected MnSOD and CAT activities. Cold-induced changes of pancreatic AD were additionally affected by the alterations in l-arginine-NO-producing pathway. Some AD changes in the same direction with l-arginine or L-NAME point to the complexity of nitrogen compounds metabolism and function, accompanied by tissue-specific response.