Biodistribution and excretion of radioactivity after the administration of 166Ho-chitosan complex (DW-166HC) into the prostate of rat.

PURPOSE: The objective of this study was to determine the fate of the 166Ho-chitosan complex (DW-166HC) in rats by examining its absorption, distribution and excretion after administration into the prostate. METHODS: About 100 microCi of DW-166HC [containing 0.1875 mg of Ho(NO3)3.5H2O and 0.25 mg of chitosan] was administered intraprostatically. The level of radioactivity in blood, urinary and faecal excretion, and radioactivity distribution were examined. To determine the effect of chitosan in DW-166HC, 166Ho nitrate alone [0.1875 mg of Ho(NO3)3.5H2O] was administered into the prostate of male rats, and radioactivity distribution was examined using whole-body autoradiography. RESULTS: After administration of DW-166HC into the prostate, cumulative urinary and faecal excretion over the period 0-72 h was 0.35% and 0.11%, respectively. The radioactivity at the administration site was extremely high at all time points up to 144 h (>98% of injected dose). The small amount of radioactivity which did transfer from the administration site distributed mainly to the liver, spleen, kidney cortex and bone. Compared with the DW-166HC group, the group that received 166Ho nitrate alone displayed three- to fourfold higher levels of radioactivity in the main tissues, including liver, spleen, kidney cortex and bone, at 24 h after administration (P < 0.05). CONCLUSION: The results of this study show clearly that most of the administered DW-166HC remained at the administration site. It is concluded that the chitosan complex may be used to retain 166Ho within a limited area in cancer of the prostate.

Effects of habitual chitosan intake on bone mass, bone-related metabolic markers and duodenum CaBP D9K mRNA in ovariectomized SHRSP rats.

We have demonstrated that the habitual intake of chitosan can decrease bone mass in ovariectomized (OVX) SHRSP rats fed a low-Ca diet (0.1%). In the present study, we examined both the etiology of bone loss induced by dietary chitosan and the preventive effect of vitamin C supplementation. Rats were OVX and maintained on one of the following diets for 6 wk: 10% cellulose (CE). 10% chitosan (CH) or 10% chitosan with sodium ascorbate (CHVC). CH caused a significant reduction in bone mineral density (BMD) and stiffness in femurs and the fourth lumbar vertebrae (L4). There was no significant difference in intestinal Ca absorption between CH and CE, whereas CH intake significantly reduced intestinal P absorption. The bone loss in CH rats was accompanied with an increase in urinary Ca excretion and a decrease in serum Ca as well as a significant increment In serum PTH and 1,25(OH)2D3. The vitamin D receptor and calcium binding protein D9K mRNAs were also significantly increased in the duodenum of CH rats. Vitamin C supplementation to CH caused an increase in the Ca and P contents of femurs as well as BMD of the L4, with a decrease in urinary Ca excretion. These results indicate that dietary chitosan with low Ca intake possibly induces the loss of bone mass by enhancing urinary Ca excretion rather than by inhibiting Ca absorption, and that vitamin C supplementation could prevent bone loss caused by chitosan through the increment of retained Ca followed by suppression of urinary Ca excretion.

Subacute toxicity of chitosan oligosaccharide in Sprague-Dawley rats.

A subacute oral toxicity study of chitosan oligosaccharide was performed in Sprague-Dawley rats of both sexes. Each 36 male and female rats were administered by gavage with 500, 1,000 and 2,000 mg/kg/day for 4 weeks (7 days/week), respectively. Examinations regarding clinical signs, body weights, hematological and biochemical parameters, and histopathological examinations were carried out. There were no significant differences in behavior or external appearance, body weight and food consumption between control and treated rats. In addition, no significant differences in urinalysis, hematology, blood biochemistry, relative organ weights and histopathological findings were found in both control and treated rats. In conclusion, it was suggested that subacute toxicity of chitosan oligosaccharide was low and the no-observed adverse effect level was considered to be over 2,000 mg/kg in rats.

Preparation of CM-chitin microspheres by complexation with iron(III) in w/o emulsion and their biodisposition characteristics in mice.

6-O-Carboxymethylchitin (CM-chitin) was partially deacetylated by alkaline treatment, and the 30% deacetylated product was named CM-DA30 and used for the preparation of microspheres. An aqueous solution of CM-DA30 was added to hexane containing 1% (w/w) sorbitan sesquioleate and emulsified by stirring and sonication, and iron(III) chloride was added. The formed microspheres (CM-MS) were washed with methanol and lyophilized after addition of polyethylene glycol. The mean particle diameter was less than a few microm, and longer sonication time tended to decrease the mean particle size. Sixty min of sonication enabled the production of CM-MS consisting of only the particles with a diameter of less than several microm. Iron(III) content and recovery of CM-DA30 were not markedly affected by the sonication time. CM-MS was spherical as was observed by scanning electron microscopy. Fluorescein moieties-containing microspheres (CM-MS-FTC) were prepared in the same manner but using fluorescein-isothiocyanate-labeled CM-DA30 (FTC-CM-DA30) instead of CM-DA30. After i.v. injection of CM-MS-FTC, its body distribution and urinary excretion of FTC-CM-DA30 were examined. CM-MS-FTC was located to some extent in the lung for an initial short time (= 1 h), soon cleared from the lung, and was retained for long in the liver and spleen. CM-MS-FTC was quickly eliminated from the blood circulation, and 60% of the dose was excreted into urine at 3 h after injection. From 3 h after injection, the urinary excretion rate markedly decreased, and the total excreted amount was 66% of the dose at 12 h after injection, which was not significantly different from that at 3 h after injection. The present preparation technique permits producing small microspheres of CM-chitin as a drug carrier possibly useful for the liver targeting.

Evaluation of N-succinyl-chitosan as a systemic long-circulating polymer.

The water-soluble, low toxic and less biodegradable chitosan derivative N-succinyl-chitosan (Suc-chitosan) was investigated for body distribution and urinary excretion on a long-time scale (24-72 h after i.v. injection) using a fluorescein-labeling technique. Fluorescein isothiocyanate (FITC)-labeled Suc-chitosan (Suc-chitosan-FTC) was characterized for molecular weight, succinylation degree and FTC content. Systemic retention and tissue distribution of Suc-chitosan-FTC were examined after i.v. administration to normal and Sarcoma 180 tumor-bearing mice. Suc-chitosan-FTC was sustained at a high level in the circulation over 72 h; that is, the plasma half-life in normal mice was 100.3 h and that in tumor-bearing mice was 43.0 h, which was longer than those of other long-circulating macromolecules reported to date. As to the tissues except blood circulation, Suc-chitosan-FTC was distributed very little in tissues other than the tumor. Although the total amount of Suc-chitosan-FTC residing in tested tissues decreased gradually, urinary excretion did not increase from 24 h after injection. These observations suggested that Suc-chitosan-FTC may be eliminated by mechanisms other than in the urine or moved to tissues other than those tested. The ratio of tumor accumulation reached a plateau at 48 h after injection, and the accumulation level, approximately 10%, was similar to those observed for other reported long-circulating macromolecules.

Biodisposition characteristics of N-succinyl-chitosan and glycol-chitosan in normal and tumor-bearing mice.

Two water-soluble chitosan derivatives, N-succinyl-chitosan (Suc-chi; average MW 3x10(5)) and glycol-chitosan (Gly-chi; average MW 1.5x10(5)), were examined concerning their biodisposition characteristics in order to evaluate their possible use as water-soluble drug carriers. Their body distribution and urinary excretion were investigated by i.v. administration of FITC-labeled Suc-chi (FTC-Suc-chi) and FITC-labeled Gly-chi (FTC-Gly-chi) to normal and Sarcoma 180 solid tumor-bearing mice. In normal mice, both polymers showed good retention in blood circulation; especially, FTC-Suc-chi exhibited a long half-life of 51 h, and its distribution to other tissues was very small. FTC-Gly-chi was distributed into the kidney to a relatively high extent. In tumor-bearing mice, FTC-Suc-chi and FTC-Gly-chi were eliminated faster from the blood circulation than in normal mice, that is, with half-lives of 11 and 7 h, respectively. FTC-Suc-chi was less partitioned to the tumor tissue but accumulated more easily into it compared with FTC-Gly-chi. This suggested the enhanced permeability and retention (EPR) effect of Suc-chi and explained the previous result that a water-soluble Suc-chi-mitomycin C conjugate injected intravenously exhibited a good effect against Sarcoma 180 solid tumor. FTC-Gly-chi showed greater distribution to the kidney than in normal mice. Urinary excretion studies indicated the faster excretion of both polymers in tumor-bearing mice. The molecular weight of the products excreted into urine indicated that both polymers should be pretty resistant to the hydrolytic enzyme, lysozyme. Taking toxicities into account, Suc-chi is considered to be available as a drug carrier showing long systemic retention and tumor accumulation.

Biodegradation and distribution of water-soluble chitosan in mice.

Randomly 50% deacetylated chitin, called Chi, was examined on the biodegradability, body distribution and urinary excretion after the intraperitoneal (ip) administration to mice. These characteristics were investigated using fluorescein isothiocyanate (FITC)-labeled Chi (FTC-Chi). The in vitro biodegradability was investigated by incubation with lysozyme and murine plasma and urine. The degradation of Chi or FTC-Chi was accelerated by lysozyme, plasma and urine. The molecular weight was checked by gel-chromatography. The degradation product showed a fairly small molecular weight and contained no FTC-Chi of a large one. The body distribution and urinary excretion of FTC-Chi were investigated at 1, 14 and 24 h after the ip injection to mice. FTC-Chi moved fast to the kidney and urine, and was scarcely distributed to the liver, spleen, abdominal dropsy and plasma. Most of FTC-Chi was excreted into urine after 14 h, and the molecular weight of the excreted FTC-Chi was as small as that of the product obtained by the long in vitro incubation. Therefore, Chi is considered to be highly biodegradable and easily excreted in urine, and further it is suggested to have no problem on accumulation in the body; however, at the same time, Chi is found not to operate as a polymer support showing long retention in the body.

Biodistribution and kinetics of holmium-166-chitosan complex (DW-166HC) in rats and mice.

UNLABELLED: The fate of 166Ho-chitosan complex, a radiopharmaceutical drug for cancer therapy, was determined by studying its absorption, distribution and excretion in rats and mice. METHODS: Holmium-166-chitosan complex [0.75 mg of Ho(NO3)3 x 5H2O and 1 mg chitosan/ head] was administered intrahepatically to male rats. Radioactive concentrations in blood, urinary and fecal excretion and radioactive distribution in tissues were examined. To determine the effects of chitosan in 166Ho-chitosan complex, 166Ho alone [0.75 mg of Ho(NO3)3 x 5H2O/head] was intrahepatically administered to male rats, and radioactive concentrations in blood, urinary and fecal excretion and radioactive distribution were examined. In B16 melanoma-transplanted nude mice, radioactive distribution after intratumoral administration of 166Ho-chitosan complex [0.075 mg of Ho(NO3)3 x 5H2O and 0.10 mg chitosan/head] was investigated also. RESULTS: After administration of 166Ho-chitosan complex, the radioactive concentrations in blood were low, and cumulative urinary and fecal excretions over a period of 0-72 hr were 0.53% and 0.54%, respectively. The radioactive concentrations in tissues and the whole-body autoradiography images showed that most of the administered radioactivity was localized at the administration site, and only slight radioactivity was detected from the liver, spleen, lungs and bones. On the other hand, results of intrahepatic administration of 166Ho alone showed high radioactive concentrations in the blood, and the whole-body autoradiographs showed that the administered radioactivity was distributed in many organs and tissues. These results strongly suggest that 166Ho is retained at the administration site only when it forms a chelate complex with chitosan. Autoradiographs after intratumoral administration of 166Ho-chitosan complex showed that radioactivity was localized at the site of administration without distribution to the other organs and tissues. CONCLUSION: Administered 166Ho-chitosan complex is retained at the administration site after either intrahepatic or intratumoral administration to rats or tumor-transplanted nude mice.