Effects of ketoconazole on rat testicular steroidogenic enzymatic activities

Ketoconazole (K) is an antifungal imidazole derivative which has been shown to be a potent inhibitor of testosterone (T) biosynthesis in rodents and humans. To study the effect of K on rat testicular steroidogenesis we measured the activities of five testicular microsomal steroidogenic enzymes in K-treated rats and controls. Thirty male adult rats were given either 2 mg K or water every 12 hours by mouth during 5 days. Mean testicular weight was similar in both groups of animals. The K-treated group had a T serum concentration of 83 +/- 14 ng/dL whereas it was 94 +/- 16 ng/dL in the control group (NS). The K-treated animals had decreased activities of the 3 beta-hydroxysteroid dehydrogenase (830 +/- 48 vs 2,245 +/- 109 pmol/mg protein/min, P less than 0.001), 17-hydroxylase (243 +/- 5 vs 676 +/- 17 pmol/mg protein/min, P less than 0.001), 17-ketosteroid reductase (31 +/- 2 vs 169 +/- 7 pmol/mg protein/min, P less than 0.001), and aromatase enzymes (92 +/- 6 vs 123 +/- 7 pmol/mg protein/min, P less than 0.01). The 17,20-desmolase activity was similar in both groups of animals (210 +/- 4 vs 171 +/- 18 pmol/mg protein/min). We conclude that K given orally to rats inhibits the activity of several testicular steroidogenic enzymes.     

Direct effect of the luteinizing hormone releasing hormone analog D-Trp6-Pro9-Net-LHRH on rat ovarian steroidogenesis

The luteinizing hormone releasing hormone analog D-Trp6-Pro9-Net-LHRH (LHRHa) inhibits rat ovarian estradiol secretion. To determine whether LHRHa decreases serum estradiol concentrations solely by inhibiting gonadotropin secretion or, in addition, by influencing directly ovarian estradiol biosynthesis, we examined the effects of LHRHa on the activities of 5 key ovarian steroidogenic enzymes. Fifty hypophysectomized, gonadotropin-treated rats were given either LHRHa (1 microgram/day) or saline sc during 7 days. The LHRHa treated animals exhibited a significant decrease in serum estradiol when compared with the control group (461 +/- 30 vs 31 +/- 5 pg/ml, mean +/- SE, P less than 0.001). The changes in estradiol concentration were associated with decreases in ovarian weight (372 +/- 19 vs 185 +/- 11 mg, P less than 0.001) and in the microsomal enzyme activities of 3 beta-hydroxysteroid dehydrogenase (156 +/- 5 vs 53 +/- 4 nmol/mg prot/min, P less than 0.001), 17 hydroxylase (4.7 +/- 0.8 vs 3.7 +/- 0.7 nmol/mg prot/min, P less than 0.002), 17,20 desmolase (279 +/- 14 vs 50 +/- 7 pmol/mg prot/min, P less than 0.001), 17 keto-steroid reductase (132 +/- 11 vs 6 +/- 1 nmol/mg prot/min, P less than 0.001), and aromatase (19 +/- 1.5 vs 0.9 +/- 0.1 nmol/mg prot/min, P less than 0.001) in LHRHa treated animals. These findings indicate that LHRHa can inhibit directly rat ovarian estradiol biosynthesis.     

Low [3H]Cytochalasin B Binding in the Cerebral Cortex of Newborn Rat

The concentrations of glucose transporter in the cerebral cortex and brainstem of neonatal (4–7 days old) and adult rats were measured using [³H]cytochalasin B binding. There was significantly lower binding in neonatal cortex (1.9 ± 0.7 pmol/mg protein) compared to adult (8.9 ± 2.5 pmol/mg protein). Scatchard analysis indicates this difference is due to a lower B_max (neonate, 9.7 pmol/mg protein; adult, 18.6 ± 1.3 pmol/mg protein). Measurement of [³H]cytochalasin B binding in microvessels prepared from cortex of adult (28.1 ± 3.5 pmol/mg protein) and neonate (12.8 ± 1.9 pmol/mg protein) indicates a lower binding in the microvasculature of neonates, whereas no such difference was seen in the binding in microvessels prepared from adult and neonatal brainstem (adult, 11.8 ± 2.3 pmol/mg protein; neonate, 9.4 ± 2.7 pmol/mg protein). In both adult and neonate brain, there is an enrichment of glucose transporters in the microvasculature.     

Ovarian steroidogenic enzyme activities during the rat estrous cycle

We have correlated the concentrations of serum LH, estradiol and progesterone with the activities of 2 ovarian steroid biosynthetic enzymes during the rat estrous cycle. Ovarian 3 β-hydroxysteroid dehydrogenase isomerase (3-βHSD) activity decreased from 29 ± 6 nmol/mg protein/ min (mean ± SEM) in diestrus, to 7 ± 0.4 nmol/mg protein/min in late proestrus (p < 0.005), and subsequently increased to 36 ± 9 nmol/mg protein/min in metestrus (p < 0.01). Ovarian 17-hydroxylase (17-OH) activity decreased from early to late proestrus (3.3 ± 0.2 vs 2.2 ± 0.2 nmol/mg protein/min, p <0.0025), and subsequently increased to 3.9 ± 0.2 in metestrus (p<0.001). Serum LH, estradiol and progesterone peaked during proestrus, and reached a nadir during estrus. We conclude that the activities of 3-βHSD and 17-OH in the rat ovary vary markedly during the estrous cycle. These changes may underlie the pattern of steroid secretion characteristic of this process.     

Treatment with tetrahydrobiopterin reduces blood pressure in male SHR by reducing testosterone synthesis

Treatment with tetrahydrobiopterin (BH(4)) reduces blood pressure in spontaneously hypertensive rats (SHR). In the present study, we tested the hypothesis that chronic BH(4) reduces blood pressure in male SHR by reducing testosterone biosynthesis mediated by increasing nitric oxide (NO). Male SHR, aged 17-18 wk, intact or castrated, were treated for 1 wk with BH(4) (20 mg.kg(-1).day(-1) ip). After 1 wk, mean arterial pressure (MAP), serum testosterone, and nitrate/nitrite excretion (NO(x)) were measured. MAP was significantly higher in intact males than castrated males (179 +/- 2 vs. 155 +/- 4 mmHg, P < 0.001). In intact males, BH(4) caused a 17% reduction in MAP (148 +/- 2 mmHg), had no effect on NO(x), and reduced serum testosterone by 85% (24.09 +/- 2.37 vs. 3.72 +/- 0.73 ng/dl; P < 0.001). In castrated males, BH(4) had no effect on MAP (152 +/- 5 mmHg) but increased NO(x) by 38%. When castrated males were supplemented with testosterone, MAP increased to the same level as in intact males (180 +/- 7 mmHg), and BH(4) had no effect on MAP (182 +/- 7 mmHg) or NO(x). NO has been shown to decrease testosterone biosynthesis. Chronic sodium nitrite (70 mg.kg(-1).day(-1) x 1 wk) decreased MAP in intact males (150 +/- 4 mmHg) but had no effect on serum testosterone (21.46 +/- 3.08 ng/dl). The data suggest that BH(4) reduces testosterone synthesis and thereby reduces MAP in male SHR, an androgen-dependent model of hypertension. The mechanism(s) by which BH(4) reduces serum testosterone levels are not clear, but the data do not support a role for NO as a mediator.     

n-6/n-3 多不饱和脂肪酸营养失衡对小鼠精子发生的影响

目的:探讨n-6/n-3多不饱和脂肪酸营养失衡对小鼠精子发生的影响。方法:健康的30只C57/B6雄鼠随机分为对照组(CON)、高脂组(HF)、花生四烯酸组(HF+AA)。喂食16周,做合笼实验并记录致孕率,通过精子动力分析仪检测小鼠精子活力和数量的变化,用Elisa试剂盒测血清中睾酮和甘油三酯水平。通过病理组织染色观察小鼠睾丸组织的形态学变化。利用Realtime-PCR的方法检测小鼠睾丸中Dazl基因表达水平的变化。结果:高脂组、花生四烯酸组与对照组相比精子活力[(16±0.01;12.33±2.83 vs72.2±12.73)%,P0.001],精子数量[(7.5±1.13;6±0.14 vs 13.87±0.35)million/m L,P0.001],致孕率[(28.57;14.29 vs 78.57)%,P0.001]及血清睾酮含量[(0.35±0.14;0.27±0.07 vs 3.51±0.7)ng/m L,P0.001]均显著性降低。高脂组、花生四烯酸组与对照组相比,血清中甘油三酯的含量显著增高[(0.74±0.04;0.74±0.04 vs 0.45±0.04)mmol/L,P0.001]。病理组织染色观察到花生四烯酸组小鼠睾丸组织出现了明显异形,曲细精管内部的初级精母细胞明显缺失,管腔中从初级精母细胞到精子的发生过程出现了变异,精子的数量也显著性下降。参与精子生成过程中的减数分裂前的有丝分裂增殖期、精原细胞的发育等过程的Dazl基因在高脂组和花生四烯酸组小鼠睾丸中的表达量与对照组相比显著降低(0.87±0.05;0.65±0.03 vs 1.07±0.04,P0.05)。结论:膳食中n-3/n-6多不饱和脂肪酸失衡会导致雄鼠精子发生发育的障碍     

Stimulatory guanine nucleotide-binding protein and adenylate cyclase activities in Bio 14.6 cardiomyopathic hamsters at the hypertrophic stage

The Bio 14.6 cardiomyopathic Syrian hamster is an animal model of human idiopathic cardiomyopathy. The pathogenesis of the disease in this animal has not yet been clearly elucidated. It is well known that α- and β-adrenergic receptors are increased in the myocardium of this animal, but that isoprenaline does not produce an augmented response. We examined the activity of cardiac stimulatory GTP-binding protein (Gs), which couple with β-adrenergic receptors to stimulate adenylate cyclase, in Bio 14.6 cardiomyopathic hamsters at 90 and 160 days of age. The cardiac norepinephrine concentration was significantly increased in Bio 14.6 hamsters compared with control hamsters (F1B) at 90 days of age (1,739±120 vs 1,470±161 ng/g wet tissue weight, p<0.05). Cardiac forskolin-stimulated adenylate cyclase activities at 90 and 160 days of age were lower in the cardiomyopathic hamsters than in the F1B controls (90 days old: 98±24 vs 122±29 pmol/min/mg protein, p<0.05; 160 days old: 74±13 vs 124±28 pmol/min/mg protein, p<0.01). Cardiac Gs activities at 90 and 160 days of age were significantly lower in Bio 14.6 hamsters than those in F1B hamsters (90 days old: 204±42 vs 259±49 pmol/min/mg protein, p<0.05; 160 days old: 156±39 vs 211±60 pmol/min/mg protein, p<0.05). We thus demonstrated functional defects in cardiac Gs protein and adenylate cyclase activity in the Bio 14.6 cardiomyopathic hamsters at 90 to 160 days of age (the hypertrophic stage of cardiomyopathy). Such defects could be one possible mechanism preventing an enhanced response to β-adrenergic stimulation in this animal and could also contribute to myocardial decompensation in the late stage of cardiomyopathy.     

Effects of age and luteinizing hormone antiserum on human chorionic gonadotropin-stimulated testosterone secretion in young male rats

The steroidogenic capacity of young male rats of different ages was studied. Two days prior to sacrifice at 5, 10, 15, 20, 25 and 30 days of age, the rats in treatment groups were given intramuscularly either human chorionic gonadotropin (HCG) at 20 I.U. twice daily/rat or luteinizing hormone (LH) antiserum (AS) at 0.25 ml twice daily/rat. Either saline or normal sheep serum (NSS) was given to control rats. The serum and testicular testosterone concentrations in the control rats averaged 0.85 +/- 0.03 ng/ml and 1.35 +/- 0.06 ng/mg testicular protein, respectively. At day-15 the serum and testicular testosterone concentrations in the HCG-treated rats had significantly increased to 9.30 +/- 0.85 ng/ml and 11.92 ng/mg of testicular protein, respectively. At the same age, the HCG-induced higher levels of serum and testicular testosterone concentrations were significantly reduced to 2.80 +/- 0.70 ng/ml and 6.02 +/- 1.00 ng/mg protein by concomitant administration of LH/AS and HCG. Our results suggest that the testosterone production in response to HCG stimulation is age-related. It was also determined that neutralization of circulating gonadotropin in LH/AS-treated rats decreased the sensitivity of Leydig cells to gonadotropin stimulation. This in vivo model should provide an excellent opportunity for the investigation of the testicular function in developing young males.     

Acute starvation affects rat adrenal steroidogenesis

To determine how starvation affects adrenal steroidogenesis we measured the activities of 3 adrenal enzymes involved in corticosterone biosynthesis in a group of adult female rats. The animals were either starved for 7 days or fed ad libitum for the same period. Relative adrenal weight and plasma corticosterone levels were increased in the experimental group of animals compared to the control group (40 +/- 2 vs 27 +/- 1 mg/100 g body weight, P less than 0.001, and 45 +/- 4 vs 30 +/- 5 ng/dl, P less than 0.05 respectively). There were no differences in plasma ACTH levels between the groups (34 +/- 5 vs 26 +/- 4 pg/ml). 11-Hydroxylase activity was increased in the starved group of animals (18 +/- 3 vs 8 +/- 2 nmol/mg protein/min, P less than 0.01). 3 beta-Hydroxysteroid dehydrogenase and 21-hydroxylase activities were not different between the groups (19 +/- 2 vs 16 +/- 1 nmol/mg protein/min, and 100 +/- 10 vs 110 +/- 10 pmol/mg protein/min respectively). These results suggest that acute starvation in rats produces an increase in adrenal 11-hydroxylase activity.     

Enhanced expression of group II phospholipase A2 in human hepatocellular carcinoma

Enzyme activity, protein contents, and mRNA contents of group II phospholipase A₂ (PLA₂) in hepatocellular carcinoma (HCC) surgically obtained from 8 patients were compared with those in either its neighboring liver tissues or control liver tissues. The PLA₂ specific activity towards the mixed micelles of 1-palmitoyl-2-oleoyl-phosphatidylglycerol and cholate was significantly greater in the tumor tissues (6.62 ± 1.46 nmol/min/mg) than those in the surrounding liver tissues (1.33 ± 0.22 nmol/min/mg) and controls (0.43 ± 0.04 nmol/min/mg). The results of immunoblot analysis using a specific anti-human group II PLA₂ antibody and of Northern blot analysis using a human group II PLA₂ cDNA as a probe demonstrated that group II PLA₂ was responsible for the increased enzyme activity. The contents of immunoreactive group II PLA₂ in the tumor tissues (8.81 ± 1.24 ng/mg) were significantly higher than those in the surrounding liver tissues (1.77 ± 0.27 ng/mg); those in the control tissues were below the analytical range of the method used. The group II PLA₂ mRNA was also significantly increased in the tumor tissues, compared with that in the surrounding liver tissues, whereas it was not detectable in th controls. This indicates that group II PLA₂ in HCC is induced at the pretranslational level.     

Hypercalcemia in association with a Leydig cell tumor in the rat: A model for tumor-induced hypercalcemia in man

The etiology of tumor-induced hypercalcemia was investigated in a transplantable Leydig cell tumor of the Fischer rat. In this model, serum calcium rose from a baseline of 10.4 ± 0.3 m mg/dl to 12.5 ± 0.4 mg/dl at day 10 and 16.4 ± 1.3 mg/dl (p<0.001) at day 13 post transplant. Urinary calcium also increased from 1.52 ± 0.17 mg/d to 3.52 ± 0.72 mg/d (Day 12, p<0.01). Serum phosphate decreased from a baseline of 7.5 ± 0.3 mg/dl to 5.5 ± 0.6 mg/dl at day 13 (p<0.05). At day 13 serum immunoreactive parathyroid hormone levels fell 76% from baseline (p<0.01). Calcitonin increased from 59 ± 2 pg/ml to 88 ± 9 pg/ml (p<0.01). The plasma prostaglandin E metabolite, 13, 14-dihydro-15-keto-PGE₂ increased from 407 ± 103 pg/dl to 647 ± 62 pg/ml (p<0.05) and the active Vit D compound 1, 25(OH)₂D increased from 94.8 ± 5.2 pg/ml to 162.3 ± 11.8 pg/ml (p<0.01). Urinary cyclic AMP did not decrease in parallel with the parathyroid hormone level and, in fact, increased from 146 ± 3 nmol/d to 172 ± 27 nmol/d (NS). Administration of the cyclooxygenase inhibitor indomethacin (20 mg/Kg/d) or hydrocortisone (50 mg/Kg/d) did not prevent the development of hypercalcemia. This model is similar to many patients with humoral hypercalcemia of malignancy who demonstrate suppression of parathyroid hormone with elevated urinary cyclic AMP excretion and may prove useful in the understanding of the responsible mechanisms.     

Characterization of the Binding of the GABA Agonist [3H]Piperidine-4-Sulphonic Acid to Bovine Brain Synaptic Membranes

Abstract: The binding of radioactive piperidine-4-sulphonic acid ([³H]P4S) to thoroughly washed, frozen, and thawed membranes isolated from cow and rat brains has been studied. Quantitative computer analysis of the binding curves for four regions of bovine brain revealed the general presence of two binding sites. In these brain regions less satisfactory computer fits were obtained for receptor models showing one or three binding sites or negative cooperativity. With the use of Tris-citrate buffer at 0°C the two affinity classes for P4S in bovine cortex membranes revealed the following binding parameters: K_D= 17 ± 7 nM (B_max= 0.15 ± 0.07 pmol/mg protein) and K_D= 237 ± 100 nM (B_max= 0.80 ± 0.20 pmol/mg protein). Heterogeneity was also observed for association and dissociation rates of [³H]P4S. The slow binding component (k_on= 5.6 × 10⁷ or 8.8 × 10⁷ M^-1 min^-1, k_Off= 0.83 min^-1, and K_D= 14.7 or 9.4 nM, determined by two different methods in phosphate buffer containing potassium chloride) corresponds to the high-affinity component of the equilibrium binding curve (K_D= 11 nM, B_max= 0.12 pmol/mg protein in the same buffer system). The association and dissociation rates for the subpopulation of rapidly dissociating sites, apparently corresponding to the low-affinity sites, were too rapid to be measured accurately. The binding of [³H]P4S appears to involve the same two populations of sites with B_max values similar to those for [³H]GABA binding to the same tissue, although the kinetic parameters for the two ligands are somewhat different. Furthermore, comparative studies on the inhibition of [³H]P4S and [³H]GABA binding by various GABA analogues, strongly suggest that P4S binds to the GABA receptors. The different effects of P4S and GABA on benzodiazepine binding are discussed.     

Neuroleptics Up-Regulate Adenosine A2a Receptors in Rat Striatum: Implications for the Mechanism and the Treatment of Tardive Dyskinesia

Abstract: Neuroleptics, which are potent dopamine receptor antagonists, are used to treat psychosis. In the striatum, dopamine subtype-2 (D₂) receptors interact with high-affinity adenosine subtype-2 (A_2a) receptors. To examine the effect of various neuroleptics on the major subtypes of striatal dopamine and adenosine receptors, rats received 28 daily intraperitoneal injections of these drugs. Haloperidol (1.5 mg/kg/day) increased the density of striatal D₂ receptors by 24% without changing their affinity for [³H]sulpiride. Haloperidol increased the density of striatal A_2a receptors by 33% (control, 522.4 ± 20.7 fmol/mg of protein; haloperidol, 694.6 ± 23.6 fmol/mg of protein; p < 0.001) without changing their affinity for [³H]CGS-21680 (control, 19.2 ± 2.2 nM; haloperidol, 21.4 ± 2.3 nM). In contrast, haloperidol had no such effect on striatal dopamine subtype-1 (D₁) and adenosine subtype-1 (A₁) receptors. Binding characteristics and the pharmacological displacement profile of the increased [³H]CGS-21680 binding sites confirmed them as A_2a receptors. Comparing different classes of neuroleptics showed that the typical neuroleptics haloperidol and fluphenazine (1.5 mg/kg/day) increased D₂ receptor densities, whereas the atypical neuroleptics sulpiride (100 mg/kg/day) and clozapine (20 mg/kg/day) did not (control, 290.3 ± 8.7 fmol/mg of protein; haloperidol, 358.1 ± 6.9 fmol/mg of protein; fluphenazine, 381.3 ± 13.6 fmol/mg of protein; sulpiride, 319.8 ± 18.9 fmol/mg of protein; clozapine, 309.2 ± 13.7 fmol/mg of protein). Similarly, the typical neuroleptics increased A_2a receptor densities, whereas the atypical neuroleptics did not (control, 536.9 ± 8.7 fmol/mg of protein; haloperidol, 687.9 ± 28.0 fmol/mg of protein; fluphenazine, 701.1 ± 31.6 fmol/mg of protein; sulpiride, 563.3 ± 27.2 fmol/mg of protein; clozapine, 550.9 ± 40.9 fmol/mg of protein). There were no differences in affinities for [³H]CGS-21680 or [³H]sulpiride among the various treatment groups. This study demonstrates that typical neuroleptics induce comparable up-regulation in both striatal D₂ and A_2a receptors. Thus, A_2a receptors might be a pharmacologic target for the development of novel therapeutic strategies to minimize the adverse effects of antipsychotic treatment.     

Diurnal variations of androgens in sexually mature male Bolivian squirrel monkeys (Saimiri sciureus) during the breeding season

To assess diurnal fluctuations of serum androgens and cortisol in adult male Bolivian squirrel monkeys, these steroids were measured at predetermined times (0300, 0900, and 2300 hours) during two separate 24-hour periods in the breeding season (January 1983 and late November 1983). A significant diurnal change in serum cortisol was noted, with a nadir of 99.9 ± 11.9 μg/dl (x? ± SEM) at 2300 hours and a peak of 168.9 ± 7.8 μg/dl at 0900 hours. Conversely, a nadir in serum testosterone was noted at 0900 hours (117 ± 26.5 ng/ml) increasing to a peak of 328.5 ± 57.9 ng/ml at 0300 hours. Serum androstenedione and dehydroepiandrosterone followed a pattern similar to testosterone, with a serum androstenedione (176.4 ± 34.9 ng/ml) and dehydroepiandrosterone (11.7 + 1.8 ng/ml) nadir at 0900 hours and a plasma androstenedione (494.5 ± 55.4 ng/ml) and dehydroepiandrosterone (32.5 ± 4.1 ng/ml) peak at 0300 hours. Parallel changes of testosterone, androstenedione, and dehydroepiandrosterone suggest a significant contribution of all three androgens from a common site, the testes. In contrast to old world primates and humans, serum androstenedione levels exceeded serum testosterone levels in this species.     

Serum T4, T3 and reverse T3 in ethanol fed rats.

To investigate the influence of chronic ethanol consumption on circulating thyroid hormone levels, male and female rats were given 20% ethanol as the only drinking solution daily for 8 weeks. Blood ethanol levels ranged 30–45 mg/L. In male rats serum T₄ decreased from the initial mean ± SD value of 5.2±1.4 to3.0 ±0.7 μg/dl; T₃ decreased from initial value of 97±14 to 66±11 ng/dl and rT₃ decreased from initial value of 19±9 to 10±1 ng/dl after 8 weeks of ethanol ingestion. Under similar experimental conditions, female rats showed a significant decrease in serum T₄ and rT₃ levels; however, T₃ levels decreased slightly but not significantly as compared to initial values. The results indicate adverse effect of chronic ethanol intake on serum thyroid hormone levels in rats.     

Testosterone dehydrogenase activity in koala liver: characterisation of cofactor and steroid substrate differences

We have studied the hepatic microsomal 17β-hydroxysteroid dehydrogenase (17β-HSD) capacity of koala (Phascolarctos cinereus) and tammar wallaby (Macropus eugenii). A detailed comparison of the activity in hepatic fractions from koala and rat was made. Hepatic microsomal NADP-supported 17β-HSD activity was significantly higher in koala (11.64±3.35 nmoles/mg protein/min), (mean±S.D.) than in tammar wallaby liver (1.52±0.79 nmoles/mg protein/min). However, when NAD was utilised as cofactor the activity was similar in both marsupial species (2.83±2.03 nmoles/mg protein/min, koala; 0.70±0.71 nmoles/mg protein/min, tammar wallaby). Data for rat indicated a cofactor preference for NAD rather than NADP (17.94±6.40 nmoles/mg protein/min, NAD; 2.18±1.04 nmoles/mg protein/min, NADP). Michaelis–Menten parameters for the kinetics of 17β-HSD testosterone oxidation by NADP and NAD were determined in the koala. The Km for testosterone was of the order of 10.0–24.0 μM (n=6) irrespective of the cofactor used, whilst the Km for NADP was 0.28–0.43 μM (n=2) and for NAD was 13.9–18.5 μM (n=2). 17β-estradiol was found to be an inhibitor of both NAD- and NADP- supported 17β-HSD activity. These findings indicate that NADP-mediated, but not NAD-mediated testosterone dehydrogenation is a major pathway of steroid biotransformation in koala liver; the reaction is less extensive in fractions from wallaby, human and rat. Such species-related differences in cofactor preference may contribute along with species differences in gene expression to observed rates of 17β-HSD activity in mammals.     

Effects of insulin infusion on glucose kinetics in normal and burned guinea pigs

The effects of a constant infusion of insulin (12 mu/kg·min for 90 min) on glucose turnover (determined by means of the primed-constant infusion of 6-³H-glucose) was evaluated in normal and burned (50% BSA) guinea pigs (gp). In burned, untreated gp, the mean plasma glucose level (gl) was increased from 129±8.2 to 205±13.7 mg/dl 90 min after burning, whereas gl was 140±14.5 mg/dl in the burned + insulin-infused animals at 90 min. The insulin infusion reduced gl from 120±5.6 to 69±5.8 mg/dl in unburned gp; the rate of glucose appearance (R_a) was reduced and the metabolic clearance rate (MCR) was increased. In the B+I gp, the insulin effectively minimized the increase in R_a which followed burning in the burned, untreated gp. However, insulin did not increase the MCR of the burned + insulin-infused group above that of the burned, untreated group. On the day following the burn, the insulin infusion decreased gl in the burned gp to the same extent as in the unburned animals and also increased MCR. We concluded that whereas there was a lack of peripheral responsiveness to the insulin infusion in the first 90 min after burning (during the shock phase), no such lack of responsiveness was evident on the second day.     

Effect of storage time and temperature on steroid and protein hormone concentrations in porcine plasma and serum

The effect of storage time and temperature of porcine blood prior to quantitation of hormone concentrations by radioimmunoassay (RIA) was evaluated. Blood from each of four luteal phase gilts was used to determine cortisol (CS) and progesterone (P) concentrations, while blood from each of four ovariectomized gilts and each of four lactating sows was used to determine luteinizing hormore (LH) and prolactin (PRL) concentrations, respectively. Blood was collected via jugular puncture from each animal within a 30-sec time period and placed into 18 heparinized and 18 nonheparinized tubes. One sample with and without heparin was stored in ice water (4°C) or at 28°C for 0.25, 2, 4, 6, 8, 12, 24, 36 or 48 hours. After storage, blood was centrifuged at 4°C and plasma or serum was collected and stored at ?20°C until quantitated by RIA. There were no differences (P>0.05) between plasma and serum concentrations (X ± SE, ng/ml) of CS (26.9 ± 0.8 vs 28.5 ± 0.8), P (24.7 ± 0.7 vs 24.8 ± 0.8), LH (2.1 ± 0.1 vs 2.2 ± 0.1) or PRL (53.2 ± 2.3 vs 52.6 ± 2.1). Similarly, storage temperature (4 vs 28°C) did not affect the concentrations of P (25.7 ± 0.8 vs 23.9 ± 0.7), LH (2.2 ± 0.1 vs 2.2 ± 0.1) or PRL (53.7 ± 2.1 vs 53.2 ± 2.3). Howver, CS concentrations decreased (P<0.05) from 28.5 ± 0.5 (4°C) to 26.9 ± 0.8 ng/ml (28°C). There was an animla x time interaction for CS concentration when plasma and serum were stored at both 4°C (P<0.001) and 28°C (P<0.003). There was also and animal x time interaction (P<0.03) for LH concentrations. The P and PRL concentrations decreased linearly by 0.0615 ng/hr (P<0.001) and 0.0625 ng/hr (P<0.004), respectively, with increased storage time.     

Protective Effect of Selenium on Aflatoxin B1-Induced Testicular Toxicity in Mice

Aflatoxins have been considered as one of the major risk factors of male infertility, and aflatoxin B1 (AFB1) is the most highly toxic and prevalent member of the aflatoxins family. Selenium (Se), an essential nutritional trace mineral for normal testicular development and male fertility, has received extensive intensive on protective effects of male reproductive system due to its potential antioxidant and activating testosterone synthesis. To investigate the protective effect of Se on AFB1-induced testicular toxicity, the mice were orally administered with AFB1 (0.75 mg/kg) and Se (0.2 mg/kg or 0.4 mg/kg) for 45 days. We found that that Se elevated testes index, sperm functional parameters (concentration, malformation, and motility), and the level of serum testosterone in AFB1-exposed mice. Moreover, our results showed that Se attenuated the AFB1-induced oxidative stress and the reduction of testicular testosterone synthesis enzyme protein expression such as steroidogenic acute regulatory protein (StAR), P450 side-chain cleavage (P450scc), and 17β-hydroxysteroid dehydrogenase (17β-HSD) in AFB1-exposed mice. These results demonstrated that Se conferred protection against AFB1-induced testicular toxicity and can be attributed to its antioxidant and increased testosterone level by stimulating protein expression of StAR and testosterone synthetic enzymes.     

Ovulation rate and serum LH levels in rats treated with indomethacin or prostaglandin E2

Serum LH levels were determined by radioimmunoassay at the normal time of the proestrous LH peak (17.30 – 18.00) and ovulatory performance was examined on the morning of estrus in rats treated with indomethacin, an inhibitor of prostaglandin synthesis. When the drug was administered at 14.30 on the day of proestrus, only 21% of the rats ovulated and the total number of ova shed was reduced to 4% of that found in the untreated control group, but there was no significant change in peak serum LH level (1122 ± 184 vs. 975 ± 240 ng/ml ± S.E., treated vs. control). Prostaglandin E₂ (PGE₂) given late on the day of proestrus (25 to 750 μ g/rat at 24.00) was effective in overcoming this antiovulatory action of indomethacin: 71–90% of the rats ovulated, though the number of eggs shed was low (24–55% of control value). Indomethacin was still effective in blocking ovulation when given at 20.00, that is after completion of the proestrous LH surge, but not at 24.00. Administration of PGE₂ (2 × 750 μ g/rat) in the early afternoon of proestrus elicited a rise in serum LH levels in rats in which the cyclic LH surge had been blocked with Nembutal (470 ± 87 vs. 106 ± 17 ng/ml ± S.E.) and induced ovulation in two-thirds of these animals.The results confirm, by direct measurement, that indomethacin does not block LH release but interferes with a late phase of the ovulatory process. PGE₂ reverses this action of indomethacin on the ovary. In addition, PGE₂ has a central effect causing LH release.