Oral activity of the growth hormone releasing peptide His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 in rats, dogs and monkeys

The purpose of this study was to evaluate the growth hormone (GH) releasing activity of orally administered His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GHRP-6, SK&F 110679) in rats, dogs and monkeys. Rats were administered GHRP-6 orally by gavage or parenterally through femoral artery catheters. Blood was collected before and after GHRP-6 administration for estimation of plasma GH and comparison of GH changes resulting from enteral and parenteral administration of the peptide. GHRP-6 was administered to dogs intravenously (i.v.) through cephalic vein catheters, intragastrically (i.g.) through esophagostomy tubes or intraduodenally (i.d.) through vascular access ports, and blood was collected before and after peptide administration for estimation of plasma GH. Cynomolgus monkeys were administered GHRP-6 i.g., and blood was collected from abdominal aorta for estimation of changes in plasma GH. Enteral activity of GHRP-6 was observed in all 3 species tested. In rats, ED50's for enteral and parenteral administration of GHRP-6 were 4 mg/kg and 28 micrograms/kg, respectively. Thus in rats, enterally administered GHRP-6 was 0.7% as bioactive as the parenterally administered peptide. In dogs GHRP-6 was slightly less potent than in rats, with ED50's for i.g. and i.v. administration approximately 15 mg/kg and 125 micrograms/kg, respectively. However, enteral potency of GHRP-6 in dogs was 0.8% of parenteral potency, and thus, comparable to that in rats. Additionally, comparison of plasma GH levels following i.g. vs i.d. administration in dogs suggested greater activity by the i.d. route. Monkeys were the species most sensitive to enterally administered GHRP-6, with plasma GH increased in those receiving i.g. doses as low as 0.3 mg/kg and an ED50 of 0.75 mg/kg compared to 4 and 15 mg/kg in rats and dogs, respectively. The results of this study demonstrate that GHRP-6 releases GH when administered directly into the gastrointestinal tract. Although enteral activity is approximately 1% of parenteral activity, GHRP-6 is potent, especially in primates which require relatively low doses to provoke GH release. These data suggest that orally active GHRP-6 may provide a practical therapeutic alternative to parenterally administered peptides such as GHRH, especially if enteral activity is enhanced with appropriate formulation.     

Influence of honey on orally and intravenously administered diltiazem kinetics in rabbits

Effect of honey on plasma concentration of diltiazem after oral and intravenous administration in rabbits, has been studied. For oral study, single dose of diltiazem (5 mg/kg, p.o.) along with saline was administered to New Zealand white rabbits (n=8). Blood samples were collected at 0, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6 and 8 hr after drug administration from marginal ear vein. After a washout period of one week, diltiazem was administered with honey (2.34 ml/kg; p.o.) and the blood samples were collected as above. To the same animals honey (2.34 ml/kg; p.o.) was continued once daily for 7 days. On 8th day, honey and diltiazem were administered simultaneously and blood samples were collected at similar time intervals as mentioned above. For intravenous study the pharmacokinetic was done in each animal on two occasions. The first study was done after single dose administration of diltiazem (5 mg/kg; i.v.) along with saline (2.34 ml/kg; p.o.). Blood samples were collected at 0, 0.083, 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4 and 6 hr after i.v. diltiazem administration. The same animals were treated with honey (2.34 ml/kg; p.o.) for seven days. On day 8, the second study was carried out with single dose i.v. administration of diltiazem along with honey (2.34 ml/kg; p.o.) and blood samples were collected. In the oral study, single dose administration of honey decreased the AUC and Cmax of diltiazem associated with significant increase in clearance and volume of distribution when compared to saline treated group. After one week administration of honey, diltiazem kinetic data showed further reduction in AUC and Cmax and increase in clearance and volume of distribution. In the i.v. study also, multiple dose administration of honey significantly reduced the AUC and increased the clearance value of diltiazem. The results suggest that honey may decrease the plasma concentration of diltiazem after its oral or i.v. administration in rabbits.     

MDL-646, a new synthetic E1-prostaglandin with local protective effects on the gastric mucosa

The gastric protection, diarrheogenic and arterial hypotensive effects of MDL-646, a PGE₁ derivative, have been studied in rats. The compound administered p.o. or i.v. was able to inhibit the maroscopic damage to gastric mucosa produced by noxious stimuli (ethanol and indomethacin). In the stomach perfusion test with the anesthetized rat, intravenously administered MDL-646 reduced histamine- or pentagastrin-stimulated gastric secretion. After intraduodenal administration (i.d.) doses at least 40–50 times greater were necessary for an antisecretory effect. In conscious rats with chronic gastric fistulas, intragastrically administered (i.g.) MDL-646 affected both acid concentration and volume of unstimulated gastric secretion. In experimental models for gastric lesions, DML-646 was much more potent after oral (p.o.) (15–30 times) than after i.v. administration. (ED₅₀ μg/kg: vs. alcohol lesions, 0.05 p.o. and 0.7 i.v.; vs. indomethacin ulcers, 7.0 p.o. and 195 i.v.). Our data would fit the hypothesis that it was a local effect on the gastric mucosa. The mechanism of this effect is not known. The supposed local activity coupled with the antisecretory effects and the good tolerability make it interesting to test MDL-646 as an anti-ulcer agent in man.     

Renal tissue injury and proliferative response after successive treatments with anticancer platinum derivatives and tobramycin

The administration of anticancer platinum derivatives such as cisplatin, or aminoglycoside antibiotics is frequently associated with tubular necrosis which can eventually lead to acute renal failure. Previously, we have shown that renal tissue injury induced by these drugs elicits a process of tissue repair involving the stimulation of cell proliferation. The present study was undertaken to examine the morphological alterations and the proliferative response resulting from tobramycin administration to animals previously challenged with the platinum derivatives cisplatin and carboplatin. Female Sprague-Dawley rats were treated i.p. with cisplatin (8 mg/kg delivered in four daily injections) or carboplatin (40 mg/kg given in one injection) and sacrificed 21 or 60 days after drug administration. Tobramycin was administered i.p. twice a day at a daily dose of 10 mg/kg over the ten days preceding sacrifice. At 1 h before sacrifice, each animal received i.p. 200 μCi of [³H] thymidine for the measurement of DNA synthesis and cell proliferation (determined by histoautoradiography). Successive treatments with cisplatin and tobramycin appeared to produce an increase in the severity of histopathological alterations such as tubular necrosis and cystic degeneration. Moreover, cisplatin pretreatment dramatically increased the severity of tobramycin-induced lysosomal phospholipidosis. Histopathological alterations were followed by an important proliferative response partly associated with tubular regeneration but also due to fibroblastic proliferation which led to peritubular fibrosis. Surprisingly, the additive effect of cisplatin and tobramycin on renal injury became particularly striking with increasing time intervals between treatments. In contrast, successive treatments with carboplatin and tobramycin did not cause significative changes of the degree of renal injury, compared with either drug given alone. In these groups we observed a moderate increase in cell proliferation which decreased with increasing intervals of time between treatments. In conclusion, the administration of tobramycin, even 2 months after cisplatin exposure, may still be hazardous. In contrast, successive treatments with carboplatin and tobramycin only seems to involve some, albeit moderate, nephrotoxic risk when the time interval between treatments is short.     

The hen's fertile egg screening test (HEST): A comparison between the acute toxicity for chick embryos and rodents of 20 drugs

The possibilities of using developing chick embryos for evaluating drug activities and toxicities were studied by determining LD₅₀ values for 20 drugs with 14 different pharmacological activities. Fifteen-day old chick embryos received drugs through the air cell and deaths were measured at 48 hr after the treatments. The LD₅₀ values were determined and compared to the i.v., i.p., s.c. and p.o. values from mice listed in the Registry of Toxic Effects of Chemical Substance. The systemic toxicity of 15-day-old chick embryos to drugs were similar to those of mice with the following exceptions. The chick embryos seemed to be more sensitive than mice to antineoplastic or antibiotic agents such as actinomycin D and doxorubicin, whereas, LD₅₀ values of cholinergic and cholinergic blocking drugs by this method were 10 to 20 fold of LD₅₀ (i.v.) of mice. These observations are important for applying the hen's fertile screening test (HEST) to the determination of drug activities other than that of embryo toxicity or teratogenic activity.Abbreviations i.v. intravenous administration - i.p. intraperitoneal administration - s.c. subcutaneous administration - p.o. oral administration - LD₅₀ acute median lethal dosage     

Pharmacokinetics of oestrone-3-O-sulphamate

The sulphatase pathway is thought to be the major route of oestrogen synthesis in breast tumours in postmenopausal women. There is currently considerable interest in developing a potent steroid sulphatase inhibitor to block oestrogen synthesis by this route. One of the most potent inhibitors discovered so far is oestrone-3-O-sulphamate (EMATE) which is active in vivo. In this study we report the preparation of a formulation for the administration of EMATE by the oral route. A method, using high-performance liquid chromatography (HPLC), was also established to measure concentrations of EMATE in rat plasma after its oral or i.v. administration. Using the oral formulation and HPLC assay, EMATE was readily detected in rat plasma after oral administration. Plasma EMATE concentrations were related to the dose of drug administered orally over the 10–40 mg/kg range. To examine the pharmacokinetics of EMATE, the compound (40 mg/kg, single dose) was administered either orally (in the formulation) or i.v. (in propylene glycol) with plasma samples being collected for up to 6 h. After oral administration, EMATE was rapidly absorbed, with the peak plasma concentration being detected at 30 min, after which plasma concentrations rapidly decreased. After i.v. administration a plasma EMATE concentration was detected at 1 h similar to that after oral administration. The clearance of EMATE from plasma followed a bi-phasic curve, showing an initial half-life of 30 min, followed by a slower half-life of 4 h 30 min. Little evidence was obtained for any metabolism of EMATE to oestrone. Rat liver sulphatase activity was almost completely inhibited (>99%) within 30 min of oral or i.v. administration of EMATE.     

MDL-646, a new synthetic E1-prostaglandin with local protective effects on the gastric mucosa

The gastric protection, diarrheogenic and arterial hypotensive effects of MDL-646, a PGE1 derivative, have been studied in rats. The compound administered p.o. or i.v. was able to inhibit the macroscopic damage to gastric mucosa produced by noxious stimuli (ethanol and indomethacin). In the stomach perfusion test with the anesthetized rat, intravenously administered MDL-646 reduced histamine- or pentagastrin-stimulated gastric secretion. After intraduodenal administration (i.d.) doses at least 40-50 times greater were necessary for an antisecretory effect. In conscious rats with chronic gastric fistulas, intragastrically administered (i.g.) MDL-646 affected both acid concentration and volume of unstimulated gastric secretion. In experimental models for gastric lesions, MDL-646 was much more potent after oral (p.o.) (15-30 times) than after i.v. administration. (ED50 micrograms/kg: vs. alcohol lesions, 0.05 p.o. and 0.7 i.v.; vs. indomethacin ulcers, 7.0 p.o. and 195 i.v.). Our data would fit the hypothesis that it was a local effect on the gastric mucosa. The mechanism of this effect is not known. The supposed local activity coupled with the antisecretory effects and the good tolerability make it interesting to test MDL-646 as an anti-ulcer agent in man.     

Rejection of tumor metastases in Fischer 344 rats following the administration of killed Corynebacterium parvum

Summary Fischer 344 rats received subcutaneous grafts of syngeneic 13762 mammary adenocarcinoma cells. Thereafter, at 20 days, each animal of a group received either daily (×2) permeating intratumor injections of killed Corynebacterium parvum (1.0 mg) saline, and weekly (×4) intravenous (i.v.) or intraperitoneal (i.p.) C. parvum or saline. In addition, a group each (4 groups) of rats were treated with surgical extirpation of the growing tumor nodule and i.v. and i.p. C. parvum or saline administered at weekly (×4) intervals. The results revealed that following intratumor injection of C. parvum there was rejection of tumor by all animals which exhibited long-term survival for 29 months (intratumor saline: 0% survival). The groups of rats treated with surgical extirpation of the tumor and parenteral administration of C. parvum exhibited 70–75% survival for 20 months (saline treated: 20–35% survival). The surviving animals exhibited tumor-specific protection to subsequent tumor cell challenges. Macrophages separated from the lung, peritoneum, and spleen of rats from the intratumor C. parvum group exhibited respectively, 46.2%, 62.9%, and 29.4% cytotoxicity towards target 13762 tumor cells as measured by ⁵¹ Cr release. Similar studies using macrophages from the group treated with surgery and parenteral C. parvum revealed similar tumor cytotoxicity (pulmonary: 49.2%; peritoneal: 65.7%; spleen: 34.4%). The splenic lymphocytes from the intratumor and parenteral C. parvum groups exhibited, respectively, 16.9% and 14.7% ⁵¹ Cr release following incubation with target tumor cells.This study was supported in part by Grant No. CA18582-01 from the National Cancer Institute     

Orally administered <Emphasis Type="Italic">Bifidobacterium</Emphasis> triggers immune responses following capture by CD11c<Superscript>+</Superscript> cells in Peyer’s patches and cecal patches

We have investigated the immunomodulatory mechanisms of Bifidobacterium pseudocatenulatum JCM7041 (Bp) as model of probiotics following oral administration to mice. This study was conducted with the aim of clarifying the mechanism of immunomodulation induced by oral administration of probiotic bacteria through elucidation of the detailed mechanism of transfer of orally administered bacterial cells within the body and the interaction between bacterial cells and cells of the immune tissues. We observed the localization of Bp in mice following oral administration, showing that Bp was surrounded by CD11c⁺ cells in Peyer’s patches (PP) and cecal patches (CP). These results indicated that Bp might induce CD11c⁺ cell-mediated immune responses directly. Furthermore, IL-10 and IL-12p40 production by Thy1.2⁻ cells, including CD11c⁺ cells, increased significantly. Production of IL-10 and IL-12p40 by bone marrow-derived dendritic cells (BMDC) was significantly increased by Bp stimulation. These results suggest that oral administration of Bp induces immune responses directly following capture by CD11c⁺ dendritic cells (DCs). Subsequently, we observed oral administration of Bp for 1 week induced IgA and IgA-associated cytokine production by CP and PP cells, suggesting that Bp induced DC-mediated immune responses on CP as well as PP.     

Renal tissue injury and proliferative response after successive treatments with anticancer platinum derivatives and tobramycin

The administration of anticancer platinum derivatives such as cisplatin, or aminoglycoside antibiotics is frequently associated with tubular necrosis which can eventually lead to acute renal failure. Previously, we have shown that renal tissue injury induced by these drugs elicits a process of tissue repair involving the stimulation of cell proliferation. The present study was undertaken to examine the morphological alterations and the proliferative response resulting from tobramycin administration to animals previously challenged with the platinum derivatives cisplatin and carboplatin. Female Sprague-Dawley rats were treated i.p. with cisplatin (8 mg/kg delivered in four daily injections) or carboplatin (40 mg/kg given in one injection) and sacrificed 21 or 60 days after drug administration. Tobramycin was administered i.p. twice a day at a daily dose of 10 mg/kg over the ten days preceding sacrifice. At 1 h before sacrifice, each animal received i.p. 200 microCi of [3H] thymidine for the measurement of DNA synthesis and cell proliferation (determined by histoautoradiography). Successive treatments with cisplatin and tobramycin appeared to produce an increase in the severity of histopathological alterations such as tubular necrosis and cystic degeneration. Moreover, cisplatin pretreatment dramatically increased the severity of tobramycin-induced lysosomal phospholipidosis. Histopathological alterations were followed by an important proliferative response partly associated with tubular regeneration but also due to fibroblastic proliferation which led to peritubular fibrosis. Surprisingly, the additive effect of cisplatin and tobramycin on renal injury became particularly striking with increasing time intervals between treatments. In contrast, successive treatments with carboplatin and tobramycin did not cause significative changes of the degree of renal injury, compared with either drug given alone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Oral—parenteral immunization leads to the appearance of IgG auto-anti-idiotypic cells in mucosal tissues

The appearance of plasma cells, specific for antigen or autologous idiotypic antibody, in rabbits immunized systemically, orally, or orally-systemically was determined using immunofluorescence techniques. Oral or parenteral immunizations alone did not lead to the appearance of anti-idiotypic cells in mucosal tissues, although IgA antigen-binding cells were observed in these sites after the oral administration of antigen. However, when rabbits were primed with orally administered antigen, followed by a regimen of concurrent oral—parenteral immunizations, IgG anti-idiotypic plasma cells were demonstrated in mucosal lymphoid tissues.     

Tissue platinum after clinical treatment with cisplatin or carboplatin in tumor-bearing patients

Tissue platinum (Pt) levels were measured in tumor-bearing patients treated with either cisplatin or carboplatin. Cisplatin was given by intra-arterial, intraperitoneal, and intravenous (iv) administrations. After death, vertebrae and intervertebral disks were removed from eight human subjects, and livers and kidneys were removed from the half of them. When cisplatin was administered intraperitoneally, Pt of the liver was higher than that of the kidney, and a high content of Pt was detected in the vertebra by comparing with the other administration methods. At the intra-arterial administration of cisplatin, Pt was mainly accumulated in the kidney. At the iv administration of cisplatin, a high level of Pt was found in the vertebra and intervertebral disk, especially at the highest value at 10.31 μg/g in the intervertebral disk of one case, whereas a low level of Pt was detected in the liver. On the contrary, it was found that the iv administration of carboplatin did not result in high accumulations of Pt in the liver, kidney, intervertebral disk, and vertebra. Therefore, Pt is accumulated in different organs, depending on the way cisplatin is administered, but Pt is accumulated least in them by the administration of carboplatin.     

Pharmacological Effects of Carboplatin-Liposomes (CPL) in Mice: A Reviev of Present Knowledge

Abstract

Carboplatin was encapsulated in reverse phase evaporation vesicles (REV) consisting of hydrogenated egg phosphatidylcholine and cholesterol (HEPC:CH) in a molar ratio of 1 : 0.25. Both antitumor effects, influence on hematopoiesis and cytokine levels were measured in mice after i.p. or i.v. injection in comparison to the free drug. In the syngeneic murine P 388 leukemia and the Meth A sarcoma liposomal encapsulation resulted in a loss of antitumor activity. On contrary, in 3/6 breast carcinomas xenografted to nude mice CPL had a superior tumor inhibiting effect compared to free carboplatin, which could be further improved by using the combination of free and liposomal drug. As reported earlier CPL induced a five- or tenfold, at least 30 days lasting increase in peripheral white blood cells after only one single i.v. or i.p. injection, respectively. A second administration in a 7–10 weeks distance was able to a repeated stimulation. The colony forming activity and the percentage of cells in S-phase were elevated in spleen cells three days after treatment of mice with CPL while these parameters remained unchanged in the bone marrow. Serum taken from CPL-treated nude or normal mice induced significantly colony formation of bone marrow cells in a soft agar culture. Concerning side effects, CPL led to a 15 days lasting blockade of RES (measured by carbon clearance), to a 7 days lasting increase of serum glutamate oxalacetate transaminase and a diminuation of body weight while the blood urea levels as parameter of kidney toxicity were in normal range. A combination of CPL with either cyclophosphamide or free carboplatin prevented the cytostatic-induced leukopenia.     

Development of a plasma high-performance liquid chromatographic assay for LY303366, a lipopeptide antifungal agent, and its application in a dog pharmacokinetic study

An HPLC assay for plasma analysis of LY303366 (I), a semi-synthetic lipopeptide antifungal related to echinocandin B (ECB), was developed to support the selection and subsequent preclinical development of I. The method involved extraction of I from plasma with the aid of solid-phase extraction (SPE) cartidges followed by reversed-phase HPLC with UV detection at 300 nm. The method is simple, selective and is applicable to dog, rat, mouse and rabbit plasma. Validation studies using dog plasma showed that the values obtained for parameters of linearity, precision and accuracy were within acceptable limits. Based on analysis of 0.3 ml of plasma, the lower limit of quantitation was 20 ng/ml. The method has been successfully applied to determine the pharmacokinetic parameters of I in the dog following intravenous (i.v.) and oral administration. Compared to first generation ECB antifungal agents, the results of the i.v. dog study indicated a 50% reduction in clearance of the drug from plasma (0.1 l/h/kg) and an 18-fold increase in the volume of distribution at steady state (1.8 l/kg). When administered orally, compound I had an absolute bioavailability of 9%; however, plasma levels remained above the MIC for C. albicans (0.005 μg/ml) through 48 h. Given the excellent potency of I and its broad spectrum of activity relative to first generation ECB antifungal agents, the assay results for I indicate the potential for its use as a broad spectrum i.v. and oral antifungal agent.     

Pharmacokinetics of bestatin and oral activity for treatment of experimental metastases

Summary Bestatin is a low molecular weight aminopeptidase inhibitor originally isolated from culture filtrates of Streptomyces olivoreticuli. The serum pharmacokinetics in mice are dependent on route of administration, with a short t1/2 (1.69 min t1/2 and 12.8 min t1/2), but a high initial serum level following i.v. administration. When administered via the i.p., s.c., i.m., or p.o. routes of administration, bestatin had serum t1/2s of 8.56, 16.91, 19.25, or 15.4 min, respectively. The maximum area under the curve (concentration×time) occurred following i.v. and i.m. administration, with a lower level following p.o. or i.p. administration. Bestatin had therapeutic activity for experimental metastases, not only following i.v., i.p., and i.m. routes of administration but also following oral administration. Because of its brief serum t1/2, bestatin's therapeutic activity depends on aggressive (either daily or twice daily injection, especially following p.o. administration) and high-dose administration. Thus, the rate-limiting aspect of bestatin's therapeutic activity appears to be associated with its pharmacokinetics.This research was supported by the National Cancer Institute, DHHS, under contract No. N01-23910 with Program Resources, Inc. The contents of this publication do not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government     

Influence on Turnover and Level of Hypothalamic Noradrenaline by a New Antihypertensive Agent (GYKI 11679)

Abstract— In an attempt to delineate the possible importance of the concentration of noradrenaline at hypothalamic noradrenergic receptor sites in a hypotensive response to a drug, the action of a new antihypertensive agent, 1-(6-morpholino-3-pyridazynyi)-2-(1-[tert-butoxycarbonyi]-2-propylidene)-diazane (GYKI 11679), on the turnover rate and the endogenous level of noradrenaline (NA) in rat hypothalamus was examined. An effective, antihypertensive i.p. dose of the compound (10 mg/kg) produced a significant but relatively short-lasting reduction in the hypothalamic noradrenaline content, whereas no change was observed in the cardiac catecholamine level. The NA turnover determinations, carried out in GYKI 11679-pretreated rats by measuring the disappearance of labeled NA at 1, 2, 3, and 5 h after the injection of the radioactive amine, showed that a 10 mg/kg i.p. dose of the compound, given 1 h prior to the i.c.v. administration of the labeled NA, increased the turnover rate of noradrenaline to a great extent. The estimated half-lives of NA in the hypothalamus of the treated and of the non-treated animals were calculated as 1.72 and 3.62 h, respectively. In vitro studies showed that the spontaneous outflow of noradrenaline from hypothalamic slices was accelerated by GYKI 11679 in a dose-dependent manner in a concentration range of 10^?5 to 10^?7m . In a 10-fold higher range, GYKI 11679 produced inhibition of both the hypothalamic and the adrenal tyrosine hydroxylase activity but did not alter DOPA-decarboxylase, dopamine-β-hydroxylase, or monoamine oxidase activities. Direct in vivo measurements of catecholamine synthesis by determining the ³H-catecholamines (CA) formed from [³H]tyrosine in the hypothalamus after an i.c.v. administration of the labeled precursor showed a moderate increase in [³H]CA formation following a 10 mg/kg dose of the compound. When GYKI 11679 was administered in a 75 mg/kg i.p. dose to rats, the transformation was reduced by –50%. Adenylate cyclase activity measurements did not show stimulatory or inhibitory actions of the drug on the NA-stimulated adenylate cyclase of the rat hypothalamus, in accordance with previous results. This suggests that the increased NA turnover (utilization) caused by an effective, antihypertensive dose of GYKI 11679 is the direct consequence of an increased outflow, which occurs primarily in the hypothalamus. The increased activity of the noradrenergic neurons in this brain region might lead to a reduced sympathetic activity in the periphery and thus to a significant decrease in blood pressure.     

Treatment of experimental Pneumocystis carinii pneumonia with 1,3-di(4-imidazolino-2-methoxyphenoxy)propane lactate.

An analogue of pentamidine, 1,3-di(4-imidazolino-2-methoxyphenoxy)propane (DMP) lactate, was tested against rat Pneumocystis carinii pneumonia (PCP). The drug was found to be highly active in the treatment of rat PCP at a dose of 1.75 mg/kg (parent molecule) when administered by intravenous (i.v.) injection (daily for 2 wk). The compound was also active against PCP when given orally, however, significantly higher doses of DMP were necessary when compared to the i.v. dosing regimen. Prophylactic doses (i.v.) of the drug also proved highly effective in preventing PCP.     

Comparison of the discriminative stimulus effects of midazolam after intracranial and peripheral administration in the rat.

Rats were trained in a two-lever drug discrimination paradigm to discriminate midazolam (0.32 mg/kg, i.p. or 1.0 mg/kg, i.p.) from the no-drug condition. After completion of i.p. and s.c. midazolam generalization gradients (0.032-1.0 mg/kg), rats were surgically implanted with unilateral cannulae into the lateral ventricles. Intracerebroventricular (i.c.v.) doses of 1.1-44.2 micrograms midazolam were delivered to unrestrained rats. Midazolam produced dose-dependent increases in drug-appropriate responding by all three routes of administration, but was 2.4- to 4.3-fold more potent when given i.c.v. than when given s.c. or i.p. Midazolam, over the dose range tested, did not produce substantial decreases in response rate by any route of administration. The discriminative-stimulus effect of i.c.v. midazolam was blocked by peripherally administered flumazenil, and such antagonism was surmounted by a 2- to 5-fold increase in the i.c.v. midazolam dose. Taken together, these data suggest that the discriminative-stimulus effects of midazolam are mediated via central benzodiazepine (BZ) receptors.     

Comparative effects of single intraperitoneal or oral doses of sodium arsenate or arsenic trioxide during in utero development.

Numerous studies have suggested that single-day intraperitoneal (IP) injection of inorganic arsenic results in failure of neural tube closure and other malformations in rats, hamsters, and mice. Most of these studies involved treatment of limited numbers of animals with maternally toxic doses of arsenic (generally As(V)), without defining a dose-response relationship. In the present Good Laboratory Practice-compliant study, sodium arsenate (As(V)) was administered IP and arsenic trioxide (As(III)) was administered either IP or orally (by gavage) on gestational day 9 to groups of 25 mated Crl:CD(R)(SD)BR rats. Only at dose levels that caused severe maternal toxicity, including lethality, did IP injection of arsenic trioxide produce neural tube and ocular defects; oral administration of higher doses of arsenic trioxide caused some maternal deaths but no treatment-related fetal malformations. In contrast, IP injection of similar amounts of sodium arsenate (based on the molar amount of arsenic) caused mild maternal toxicity but a large increase in malformations, including neural tube, eye, and jaw defects. In summary, neural tube and craniofacial defects were observed after IP injection of both As(V) and As(III); however, no increase in malformations was seen following oral administration of As(III), even at maternally lethal doses. These results demonstrate that the frequently cited association between prenatal exposure to inorganic arsenic and malformations in laboratory animals is dependent on a route of administration that is not appropriate for human risk assessment.     

The influence of temperature on antiproliferative effects, cellular uptake and DNA platination of the clinically employed Pt(II)-drugs

Cellular uptake of a drug is one of the most important factors influencing its pharmacodynamics and pharmacokinetics. Our laboratory has previously studied platinum uptake following cisplatin, carboplatin and oxaliplatin treatment at sub-lethal doses of selected tumour cell lines. Here we report on the influence of temperature on dose-dependent antiproliferative effects, cellular uptake and DNA platination of these platinum-based drugs tested on MCF-7 human mammary carcinoma cell line. Inductively coupled plasma-mass spectrometry (ICP-MS) technique has been chosen to perform Pt determinations on cells treated with drug concentrations similar with those usually found in vivo in human plasma. The high sensitivity and analytical rapidity of this technique made possible to carry out a very large amount of Pt determinations (about 300) necessary for this study. Hyperthermia (43 degrees C) proved a synergistic effect with cisplatin on cell growth inhibition, while only an additive effect was demonstrated for carboplatin and oxaliplatin. This behaviour might be explained by the higher DNA platination ratio between data at 43 and 37 degrees C of cisplatin with respect to those of carboplatin and oxaliplatin.