Testing of endocrine active substances using an enhanced OECD test guideline 407: Experiences from studies on flutamide and ethinylestradiol

Groups of five male and five female Wistar rats were treated by gavage with 0, 1, 10, and 100 mg/kg body weight (b.w.) flutamide (FLU) or 0.01, 0.05, and 0.2 mg/kg b.w. of ethinylestradiol (EE2) for at least 28 days according to an enhanced Organization for Economic Cooperation and Development (OECD) test guideline (TG) 407 to investigate which of the current and/or additional parameters would detect effects on the endocrine system and to provide data on intralaboratory variability. Two identical studies were performed in parallel on each compound. Common enhancements were determination of thyroid hormones (T3, T4) and thyroid stimulating hormone (TSH), of the stage of the estric cycle to ensure necropsy of females in diestrus, of the number and morphology of epididymal sperm, and of additional organ weights (e.g., male accessory sex organs, MASO) and histopathology of additional organs (e.g., pituitary, vagina). Endocrine-mediated findings consistently observed in these studies were decreased relative weights of MASO at 100 mg/kg FLU and at 0.2 mg/kg EE2, histological changes in pituitary and testes at > or = 10 mg/kg and in MASO, epididymis and adrenals at 100 mg/kg in FLU-treated males, histological changes in the mammary gland at > or = 0.05 mg/kg and in testes, MASO and adrenals at 0.2 mg/kg in EE2-treated males, estrogenization of uterus and vagina (despite necropsy in diestrus) at > or = 0.01 mg/kg EE2, and changes in the ovary at 0.2 mg/kg EE2. Spermatology was insensitive (EE2) or revealed changes only at the maximum tolerated dose (MTD). Determination of T3, T4, and TSH did not contribute to the detection of the endocrine effects (FLU) or provided equivocal results. Doubling the group size to 10 animals by combining the studies run in parallel did not increase the sensitivity of detection of endocrine-mediated effects above the level obtained by histopathological examination of groups of five animals. Only some of the proposed enhancements evaluated were helpful in detecting the endocrine-mediated effects of FLU and EE2. Evaluation of studies according to an enhanced TG 407 on 10 compounds with different endocrine activities will identify the most appropriate enhancements.

Sensitive detection of the endocrine effects of the estrogen analogue ethinylestradiol using a modified enhanced subacute rat study protocol (OECD Test Guideline no. 407)

Groups of five male and female Wistar rats were treated by gavage with 0, 0.01, 0.05 or 0.2 mg/kg body weight of the known synthetic estrogen ethinylestradiol for 28-32 days according to a modified enhanced OECD Test Guideline no. 407 in order to investigate which of the current and/or additional parameters would detect effects on the endocrine system reliably and sensitively and to provide data on intra-laboratory variability. Two identical studies (A and B) were run concurrently. The modified enhanced protocol requests the additional determination of triiodothyronine, thyroxine and thyroid-stimulating hormone (TSH), of the stage of the estrous cycle to ensure necropsy of all females in diestrus, of the number and morphology of cauda epididymal spermatozoa, and of additional organ weights (ovaries, uterus, thyroid, and male accessory reproductive organs), and histopathology of additional organs (pituitary, epididymides, coagulation glands, pancreas, and vagina). There were no treatment-related mortalities, clinical signs or changes in behavioral parameters. In male rats, 0.2 mg/kg was the maximum tolerated dose (MTD) resulting in reduced body weight gain. The only treatment-related alteration in hematological parameter was prolonged blood clotting time in high-dose females of both studies. Changes in clinical chemistry observed in study A were elevated alkaline phosphatase activity (high-dose females) and triglyceride levels (mid- and high-dose females and high-dose males). Changes in thyroid hormones and TSH of treated animals showed high variability with no clear dose-dependency, and could not be clearly related to estrogenic activity. In accordance to a suppression of the hypothalamic-pituitary-gonadal axis, decreased relative organ weights of the male accessory reproductive organs were obtained in both studies at the high dose. Corresponding histological changes were degeneration of the testicular germinal epithelium and atrophy of Leydig cells and of all accessory sex glands. Atrophy of the coagulating gland (study A) and seminal vesicles (study B) was also seen at 0.05 mg/kg. A marked increase in relative adrenal weight in male rats, accompanied by decreased vacuolization of zona fasciculata cells observed in both studies at the high dose seems to reflect an activation of the hypothalamic-pituitary-adrenal axis. The male mammary gland was sensitively affected. Increased numbers of small basophilic over large acidophilic cells indicated an estrogen-mediated feminisation and were detected at the low (study A) or mid dose (study B). Co-mitogenic properties of estrogens in rat liver were reflected by increased relative liver weights in females at the mid and high dose of study A and also at the high dose in study B. No treatment-related changes in endocrine organ weights were observed in treated females. Histological changes in the ovaries were increased numbers of apoptotic corpora lutea (from mid dose, study B) and of early stage follicles at the high dose in both studies. Classical direct estrogenic effects on the uterus, i.e. an increased height of luminal and glandular epithelium and increased granulocytic infiltration of the endometrium, were observed even at the low dose in both studies. Uterine findings occurring with a greater variability were dilation, squamous metaplasia of glands and thickened walls. Although females were necropsied in diestrus, as diagnosed by vaginal cytology, typical signs of estrogenic action in the vagina such as keratinization (indicative of estrus in normally cycling rats), mucification (indicative of proestrus), or thickened epithelia were observed in both studies even at the lowest dose. This unexpected discrepancy between vaginal cytology and vaginal and uterine morphology of treated females was considered to be treatment-related as it was not observed in the controls. Studies on liver enzymes that were performed outside the scope of the enhanced protocol showed that ethinylestradiol at 0.2 mg/kg decreased the activity of the sex-specific testosterone-dependent liver enzyme CYP2C11 in male rats. A simulation of doubling group size (to ten animals) by combining both studies did not increase the sensitivity of detection of endocrine-mediated effects above the level already obtained by histopathological examination of groups containing five animals. Only some of the enhancements to the current OECD Test Guideline no. 407 evaluated in this study (additional organs weights and additional histopathological investigations) were helpful in detecting the endocrine-mediated effects of ethinylestradiol, while other enhancements did not contribute towards this aim. Spermatology was completely insensitive at the MTD and measurement of thyroid hormones and TSH did not contribute to increased sensitivity. Vaginal cytology appeared to be an unreliable procedure for estrous cycle staging in estrogen-treated animals. Ongoing investigations, according to the modified version of the enhanced OECD Test Guideline no. 407 protocol, into the interference of ten compounds with the endocrine system by different mechanisms will result in the identification of the most appropriate enhancements.

Feasibility and potential gains of enhancing the subacute rat study protocol (OECD test guideline no. 407) by additional parameters selected to determine endocrine modulation. A pre-validation study to determine endocrine-mediated effects of the antiandrogenic drug flutamide

Groups of five male and five female Wistar rats were treated by gavage with 0, 1, 10, and 100 mg flutamide/kg body weight for at least 28 days to investigate whether proposed enhancements to the current subacute rodent OECD test guideline no. 407 could be included into the testing routine, which of the current and/or additional parameters would detect endocrine-mediated effects of flutamide reliably and sensitively, and to provide information on intra-laboratory variability. Two identical studies were performed concurrently. The enhanced protocol requests the additional determination of the specific hormones triiodothyronine, thyroxine, thyroid stimulating hormone, follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol, prolactin, testosterone, corticosterone; of oestrus cyclicity and necropsy of all females in the dioestrus stage; of the number of homogenization-resistant testicular spermatids and the number, motility, viability, and morphology of cauda epididymal spermatozoa; of additional organ weights (pituitary, ovaries, uterus, thyroid, male accessory reproductive organs); and of the histopathology of additional organs (pituitary, epididymides, coagulation glands, pancreas, vagina). From a technical standpoint, it was possible to conduct a study according to the enhanced protocol, however, with substantial additional effort, an increase in costs by some 67%, and logistic problems. In line with the specific pharmacological effect of flutamide, treatment-related changes were mainly found in male rats, while females were hardly affected by 100 mg/kg. In male rats, 100 mg/kg was the maximal tolerated dose resulting in reduced body weight gain, but no or little other effects on clinical, haematological, clinico-chemical, or behavioral parameters, and 1 mg/kg was the no-observed-adverse-effect level. Antagonism of peripheral androgen receptors by flutamide resulted in decreased relative organ weights of male accessory reproductive organs, changes that were reliably detected in both studies at 100 mg/kg, but only in one of both studies at 10 mg/kg. Corresponding histopathological changes were also detected reliably at 100 mg/kg. Antagonism of central androgen receptors by flutamide increased LH and FSH levels. LH stimulation of testicular Leydig cells in turn increased testosterone and estradiol levels. Again, all these changes were detected reliably at 100 mg/kg, but only in one of both studies at 10 mg/kg. Corresponding histopathological alterations (increase of LH- and FSH-secreting cells, Leydig cell hypertrophy) were detected reliably and sensitively at 10 mg/kg. Studies on liver enzymes performed outside the scope of the enhanced protocol showed that flutamide at 100 mg/kg generally induced hepatic enzyme activities, but decreased the activity of the sex-specific testosterone-dependent liver enzyme CYP2C11 in male rats. The laboratory methods employed yielded reliable results, i.e., 93.6% of the quantitative measurements obtained in both studies were in agreement. Doubling the animal number from five to ten per sex and dose does not increase the sensitivity of detection of endocrine-mediated effects above the level already provided by histopathological examination of groups of five animals. Some of the proposed enhancements evaluated (additional organgravimetry and histopathology) were helpful in detecting the endocrine-mediated effects of flutamide reliably, while others did not contribute towards this aim (spermatology resulted in doubtful effects, female cyclicity was not affected, hormone determinations provided mechanistic information). Ongoing testing according to the revised version of the enhanced OECD test guideline no. 407 protocol and using ten compounds interfering with the endocrine system by different mechanisms will result in the identification of the most appropriate enhancements.

Cations of cisternal cerebrospinal fluid in humans and the effect of different doses of nimodipine on CSF calcium after stroke

Cisternal samples of cerebrospinal fluid (CSF) were analyzed for protein, albumin, sodium (Na), potassium (K), and calcium (Ca) content in 21 control subjects and 64 patients who had experienced acute stroke. A second cisternal CSF sample was taken in 37 of the stroke patients after 2-3 weeks treatment with the calcium antagonist nimodipine. Increased permeability of the blood-brain barrier was reflected by the significantly higher CSF/serum ratio of albumin in stroke patients than in control subjects (0.0046 vs. 0.0028,p = 0.0012). Serum and CSF concentrations of Na, K, and Ca did not differ between control subjects and stroke patients. In control subjects and in stroke patients, concentration of calcium in cisternal CSF ([Ca]) was smaller than values reported by others in lumbar samples. In stroke patients, the pH of CSF was lower than that of simultaneously taken blood (7.38 vs. 7.44, p < 0.001). No differences between stroke patients and control subjects were found for the cisternal CSF/serum ratios of Na (1.0 and 0.99), K (0.61 and 0.63), and Ca (0.25 and 0.24). When patients and controls were pooled together, CSF total [Ca] correlated weakly with serum total [Ca] (Spearman r = 0.28, p = 0.014) and with serum ionized [Ca] (Spearman r = 0.27, p = 0.016). After 2-3 weeks of nimodipine treatment, CSF [Ca] was significantly lower in the subgroup treated with 60 mg nimodipine four times daily (240 mg/d) than with 30 mg four times daily. A nimodipine dosage of 30 mg four times daily (120 mg/d) did not affect CSF [Ca]. A 240 mg daily dosage, but not a 120 mg daily dosage, of nimodipine may affect the Ca transport system in humans at the choroid plexus.

Serotonin (5-HT1A-receptor) agonist-induced collecting duct vacuolation and renal papillary necrosis in the rat

General anxiety in humans is treated with azaspirodecanedions, which act through a reduction of serotonin transmission. Ipsapirone also represents a serotonin (5-HT1A) receptor agonist and was under development as an anxiolytic drug. Histopathologic evaluation of animal experiments revealed cellular swelling and/or vacuolation of renal papillary and medullary collecting duct (MCD) epithelium in rats but not in dogs or mice. The changes ensued already after 1 wk of dosing and were first localized in the inner MCDs. Longer treatment periods showed that these changes proceeded from proximal to distal, approaching the papillary collecting ducts. The changes were most likely the result of altered hemodynamics in the papillary tip. Swelling resulted in partial or total papillary necrosis in some cases. Furthermore, rats treated with ipsapirone showed a sharp and transient rise in urinary endothelin excretion. Concomitantly, urinary PGE2 levels were elevated. In contrast, no elevated levels of endothelin were detected in urine samples of patients from a volunteer study, leading to the conclusion that the human kidney is not susceptible to the ipsapirone-induced alterations seen in the collecting ducts of rats.

Monoclonal antibody to tumor necrosis factor--alpha prevents lethal endotoxin sepsis in adult rhesus monkeys

In a rhesus monkey endotoxin sepsis model established by intravenous administration of 300 mg/kg D-galactosamine and 0.1 microgram/kg lipopolysaccharide from Salmonella abortus equi, hemodynamic, respiratory, metabolic and hematologic variables; levels of blood gases; monkey leukocyte elastase levels, and blood plasma concentrations of tumor necrosis factor--alpha (TNF) were monitored for 6 hours after administration, and again after 24 hours. Thirty minutes after administration of lipopolysaccharide, either 15 mg/kg anti-TNF monoclonal antibody (MoAB; n = 6) or vehicle placebo (saline solution; n = 4) were given intravenously. During this short-term experiment the organ functions were not different between the treatment groups. However, anti-TNF MoAb afforded morphologic protection from heart, lung, liver, and kidney damage after lipopolysaccharide challenge. Coagulation responses (platelet count and levels of fibrinogen, antithrombin III, and thrombin-antithrombin III complex) were smaller in anti-TNF MoAB-treated monkeys. Plasma TNF levels (WEHI cell cytotoxicity assay) reached a peak (350 pg/ml) 60 minutes after lipopolysaccharide administration in vehicle control subjects but no TNF was detected in the anti-TNF MoAB-treated monkeys. All control animals died 67 +/- 30 hours after lipopolysaccharide administration from multiorgan failure. On the contrary, all anti-TNF MoAB-treated animals survived 14 days (p > 0.005 vs placebo group mortality). Thus in short-term monkey experiments our study indicates protection against lipopolysaccharide-induced endotoxin sepsis by anti-TNF MoAB, which may have clinical relevance for the treatment of human septicemia.