Effect of chronic oral pentoxifylline administration on murine erythrocyte deformability.

BACKGROUND: Pentoxifylline has been reported to increase radiation sensitivity in vivo. We sought to evaluate whether this effect is mediated by changes in murine erythrocyte flexibility. METHODS: Pentoxifylline was administered via liquid or solid diet to young adult male CF-1 mice for 1-6 weeks. After 1, 3, and 6 weeks of drug administration, plasma levels of pentoxifylline and major derivatives were measured and erythrocyte deformability was assessed by rheoscopy, a technique which permits direct measurement of individual cellular dimensions. RESULTS: Contrary to prior reports, we found no discernible effect of the drug on erythrocyte deformability. CONCLUSIONS: The beneficial effect of pentoxifylline administration on radiation sensitivity in tumor-bearing mice is mediated by other mechanisms.

Testicular circulatory isolation: not a cause of immune-mediated testis injury in the rat.

BACKGROUND: Testicular circulatory isolation (TCI), a regional drug exclusion approach designed to prevent chemotherapy-induced male infertility, can reduce testicular drug exposure and preserve fertility. The immunological sequelae of this surgical procedure were investigated. METHODS: Forty Sprague-Dawley rats received unilateral TCI for 45 min and were killed at intervals of up to 43 days later. Testicular histology was evaluated qualitatively using hematoxylin and eosin stain, a direct immunofluorescent technique for detection of antigen-antibody complexes, and an indirect immunofluorescent technique to detect circulating antitestis antibodies. RESULTS: No immune-mediated injury was evident up to 43 days after TCI. CONCLUSION: The current work, taken together with previously published data, indicate that TCI produces no immunological damage in the rat testis. Because TCI is well tolerated in humans, this work also supports the institution of human clinical trials of this technique in men about to receive fertility-threatening chemotherapy.

In vitro and in vivo expression of opioid and sigma receptors in rat C6 glioma and mouse N18TG2 neuroblastoma cells.

Mouse N18TG2 neuroblastoma and rat C6 glioma cell lines were injected into male nude mice, and the tumors were passaged serially. At each generation, tumors were analyzed for delta opioid binding using [3H][D-Ala2,D-Leu5]enkephalin and for sigma 1 and sigma 2 binding with 1,3-[3H]di-o-tolylguanidine in the presence and absence of 1 microM pentazocine. Receptor density (Bmax) and affinity (KD) were estimated by homologous competition binding assays. Opioid and sigma Bmax values in the solid tumors were significantly lower than their original levels in vitro. KD values for opioid/sigma ligands were similar in vitro and in vivo. With successive passages in the murine host, delta opioid and sigma 1 binding of the neuroblastoma-derived solid tumors became undetectable. In contrast, sigma 2 receptor Bmax values were unchanged with successive passages of the neuroblastoma-derived tumors and doubled in the nude mouse-borne gliomas. When neuroblastoma-derived solid tumors that were devoid of delta opioid binding were returned to culture, opioid receptors appeared to be up-regulated as compared with their original in vitro levels. Serial passaging of these recultured cells in vivo again resulted in a rapid decline in opioid receptor content. The opioid data are consistent with our prior findings on opioid binding diminution in human brain tumors. The pattern of change for sigma binding was more complex, with the sigma 2 response in late passages of the glioma being reminiscent of the formerly observed increase in number of sigma sites in transformed human meninges, kidney, and colon tissue.

Serum levels of pentoxifylline and its metabolites in non-tumor-bearing mice after chronic oral pentoxifylline administration.

Pentoxifylline lowers blood viscosity and increases erythrocyte flexibility in patients with atherosclerosis, thus increasing tissue oxygen delivery. Since tumor neo-vessels are associated with tissue hypoxia, which contributes to failure of radiation therapy, pentoxifylline might also be useful as a radiation sensitizer. Such drugs are often evaluated in the murine model, but serum levels of pentoxifylline and its metabolites have not been determined in the mouse after chronic oral dosing. We investigated this by administering pentoxifylline via liquid diet or solid diet to young adult male CF1 mice for one to six weeks and assaying plasma for the parent drug and its metabolites. At one, three, and six weeks, plasma levels of pentoxifylline and major derivatives were consistently detectable. Mice remained healthy during this period, indicating that ingestion of large amounts of this drug is well tolerated.

Distribution and metabolism of pentoxifylline in non-tumor-bearing mice.

Pentoxifylline increases tissue oxygen delivery in patients with atherosclerotic arterial disease by several mechanisms, including lowering blood viscosity and increasing erythrocyte flexibility. Since tumor neo-vessels are also abnormal and associated with intra-tumoral hypoxia and, thus, with radiation failure, pentoxifylline might also be useful as a radiation sensitizer. The mouse is frequently used to study such drugs, but the pharmacokinetics of pentoxifylline in the mouse have not been determined. We investigated this in three separate experiments by administering pentoxifylline intraperitoneally, subcutaneously, or orally. Plasma was assayed for the parent drug and its metabolites by capillary gas chromatography. High plasma levels of pentoxifylline and both major derivatives occurred within several minutes after intraperitoneal or subcutaneous injection, but plasma levels were low after oral administration.

Testicular cytotoxicity of intravenous procarbazine in rats.

Although the testicular cytotoxicity of procarbazine has been evaluated in the rat, previous models have utilized routes other than the intravenous one, and have generally employed multiple-dose regimens. In this report, we describe testicular toxicity in the Sprague-Dawley rat following a single intravenous bolus of procarbazine (0-700 mg kg body weight), with necropsy 59 +/- 2 days later. Testicular toxicity was evaluated qualitatively by histology and quantitatively by testicular weight, sperm head count, repopulation index and epididymal index. Effects of procarbazine on heart, lung, liver and kidney histology were evaluated qualitatively. Progressive dose-dependent testicular atrophy and oligospermia occurred at low and intermediate dosages of procarbazine. Marked testicular atrophy, oligospermia and germinal hypoplasia were observed at high dosages (500 and 700 mg kg-1 body weight). LD50 at day 59 for procarbazine appears to be approximately 600 mg kg-1 body weight using this regimen. This model will facilitate the study of techniques to avoid drug-induced testicular damage.

Preservation of fertility following doxorubicin administration in the rat.

Several hundred thousand men receive chemotherapy each year; many are sterilized by this treatment. Testicular circulatory isolation (TCI), a regional drug exclusion approach to circumvent chemotherapy-related infertility, lessens doxorubicin-induced testicular injury in the rat. We evaluated the effect of TCI on doxorubicin-induced infertility in this study. Thirty-two eight-week-old male Sprague-Dawley rats were used. Eight rats received TCI for 45 min. Eight received doxorubicin (i.v. bolus) plus sham surgery. Eight received i.v. doxorubicin given immediately after institution of TCI. Eight controls received sham surgery alone. Mating studies began 2 months later. Six of the 8 males receiving TCI alone were fertile. In the doxorubicin-treated, sham-operated group, 0 of 7 animals were fertile. In the doxorubicin-treated group which also received TCI, 2 of 7 males were fertile. In the sham-operated group, all 8 rats were fertile. This is the first evidence that regional drug exclusion technique can improve fertility in this model.

Distribution and metabolism of doxorubicin in rats undergoing testicular circulatory isolation.

Several hundred thousand men receive chemotherapy each year; many are sterilized by this treatment. Temporary testicular circulatory isolation (TCI), a regional drug delivery approach to circumvent this, decreases doxorubicin-induced testicular injury in the rat and provides partial protection from doxorubicin-related infertility. We evaluated the distribution of doxorubicin and its metabolites (doxorubicinol and doxorubicin aglycone) in rats treated with TCI. In each of 56 male Sprague-Dawley rats, the left spermatic cord and gubernaculum were mechanically clamped for 45 minutes. Immediately after clamp application, these rats received doxorubicin (6 mg/kg, intravenous bolus) and were killed at seven time points after doxorubicin administration, ranging from 30 minutes to 48 hours. Twenty-one control rats were treated identically but did not receive TCI. Doxorubicin and its metabolites were extracted from tissue (left testis, right testis, left kidney, heart, left lung, liver) and serum and analyzed by high-performance liquid chromatography. In the TCI group, the distribution of the parent drug and doxorubicinol in tissue and serum closely approximated levels from doxorubicin-treated controls not receiving TCI in all organs except left testis. No anthracycline was detected at any time point in the left testis of the TCI group. These results indicate that TCI completely protects the testis from doxorubicin exposure in this model and that TCI does not affect distribution of doxorubicin in other organs.

Desipramine modulation of sigma and opioid peptide receptor expression in glial cells.

Exposure of C6 glial cell cultures to desipramine induced the appearance of opioid receptors and up-regulated sigma receptors. Opioid binding was demonstrated with 3H-etorphine and 3H-dihydromorphine (DHM), but was not observed with the mu, delta and kappa ligands 3H-DAMGE, 3H-DADLE or 3H-(-)ethylketocyclazocine in the presence of specific blockers, respectively. Competition experiments with 3H-DHM and either (-)naloxone or (+)naloxone indicated the presence of authentic opioid receptors. In similar studies with beta-endorphin, its truncated form (1-27) or their N-acetyl derivatives, beta-endorphin proved to have the highest affinity. Opioid receptors in glial cell aggregates were primarily kappa, with few mu and delta sites. Desipramine increased Bmax values for kappa but not mu and delta.

Implantation of tumor xenografts in nude mice: an improved methodology.

Xenografting of neoplasms is a common technique in cancer research. Implantation of non-uniform tumor tissue fragments often yields tumor nodules of irregular size and shape, which is disadvantageous. We therefore developed a device to standardize size and shape of such implants. This instrument is effective, inexpensive to fabricate, and simple to use.

Long-term outcome following testicular ischemia in the rat.

Male germ cells are quite sensitive to interruption in blood flow. Eight weeks after subjection to 45 minutes of testicular ischemia, the spermatogenic epithelium of the rat remains significantly damaged, though other cell types are well preserved. The authors evaluated the testicular recovery of the rats at 8 and 72 weeks after the 45-minute period of warm ischemia. Twenty-eight rats were studied: 14 underwent 45 minutes of total left testicular ischemia; 14 received no treatment. Four rats from each group were necropsied at 8 weeks to document the ischemic injury. At 72 weeks, the 18 surviving rats were necropsied to evaluate the long-term outcome of the treatment. At 8 weeks, significant left testicular injury was documented. However, at 72 weeks there was no difference in testicular weight or sperm head count between the groups: in all 36 testicles, the repopulation index was 1.00, the epididymal index was 3+, the modified Johnsen index was 14, and the spermatic cord score was 7 (all are maximum obtainable scores). Neither contralateral orchiopathy nor injury to spermatic cord structures was observed. Our work shows that ischemia-induced testicular injury is fully reversible with time in this model.

Effect of cyclosporine on carcinogenesis induced in rats by N-methyl-N'-nitro-N-nitrosoguanidine.

Cyclosporine administration has been associated with the development of lymphomas in human transplant patients as well as animals. Its effect on the genesis of common epithelial carcinomas is unknown. To investigate this N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was administered in drinking water to Wistar rats. Seventy-five young healthy male animals were divided into six groups and received cyclosporine alone, cyclosporine followed by MNNG, MNNG alone, cyclosporine during MNNG administration, MNNG followed by cyclosporine, and no treatment. Cyclosporine seemed to have minimal overall health effects and no cancers were encountered in the group receiving this agent alone. Animals in all carcinogen-treated groups developed gastric and upper intestinal carcinomas by Week 39. No statistically significant differences among carcinogen-treated groups were evident with respect to tumor incidence, histology, or distribution. There appeared to be trends (not statistically significant) toward a greater incidence of small bowel carcinomas in animals receiving cyclosporine plus MNNG as compared to those receiving MNNG alone; greater multiplicity of small intestinal carcinomas in animals receiving cyclosporine after MNNG as compared to all other groups; and greater incidence of small bowel tumors greater than 1 cm3 in animals receiving cyclosporine after MNNG as compared to all other groups. The median total tumor volume in the animals receiving cyclosporine following carcinogen was significantly greater than in any other group. This study does not support a policy of aggressive surveillance for gastrointestinal carcinoma in the human population receiving cyclosporine.