Excretion into gastrointestinal tract of irinotecan lactone and carboxylate forms and their pharmacodynamics in rodents.

PURPOSE: To investigate the excretion of irinotecan hydrochloride (CPT-11) and its active metabolite, SN-38, into the gastrointestinal lumen via the biliary and/or intestinal membrane route after dosing with lactone and carboxylate forms of CPT-11, and to evaluate the toxic and antitumor effects of the two forms. METHODS: The excretions of CPT-11 and SN-38 were investigated by the in situ perfusion technique using rats. The incidence of delayed diarrhea was evaluated after i.v. dosing (60 mg/kg) with CPT-11 lactone and carboxylate forms for 4 days. Antitumor activity and changes in body weight were investigated in mice with Meth A tumors. RESULTS: The excretion of CPT-11 into bile was greater in dosing with CPT-11 carboxylate than that with its lactone form, whereas the exsorption across intestinal membrane was greater in dosing with CPT-11 lactone than that with its carboxylate form. Dosing with CPT-11 lactone dose-dependently inhibited the increase in tumor weights in Meth A tumor mice, whereas the dosing with its carboxylate form reduced the antitumor effect. CONCLUSIONS: The decreased antitumor effect caused by dosing with the CPT-11 carboxylate form could be due to less accumulation in the tissue including tumor cells resulting from the rapid elimination of the form in the body.

Adrenomedullin increases phosphatidylcholine secretion in rat type II pneumocytes.

Adrenomedullin, a novel hypotensive peptide, has been reported to be produced in the lung as well as in the adrenal medulla. However, the effect of adrenomedullin on lung function is still poorly understood. In this study, we detected the expression of both adrenomedullin mRNA and putative adrenomedullin receptor mRNA in primary cultures of rat type II pneumocytes. Adrenomedullin increased the secretion of phosphatidylcholine, the predominant component of pulmonary surfactant, by type II pneumocytes. The increase was partly inhibited by pretreatment with the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP-(8-37). Furthermore, the increased phosphatidylcholine secretion was significantly inhibited by several protein kinase C inhibitors, such as sphingosine, 2-[1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl]3-(1H-indol-3-yl) maleimide (Gö6983), 3-[1-(3-amidinothio)-propyl-1H-indoyl-3-yl]3-(1-methyl-1H-++ +indoyl-3-yl ) maleimide methane sulfonate (Ro-31-8220), and staurosporine. Our results suggest that adrenomedullin can be considered a candidate autocrine modulator of surfactant secretion in type II pneumocytes.

Drug exsorption from blood into the gastrointestinal tract.

Drugs are exsorbed from the blood across the gastrointestinal membranes by passive or active processes. In the case of a passive transport mechanism, the exsorption of drugs depends on the concentration gradients between the serosal and mucosal sides. The extent of secretion (exsorption) is determined by numerous factors such as extent of binding to serum proteins, distribution volume, lipophilicity, pKa and molecular size of drugs, and the blood flow rate in the gut. Specific transport systems such as P-glycoprotein (P-gp), organic cation and organic anion transporters are found to be involved in active intestinal secretion of drugs. Intestinal secretory transport systems reduce the extent of drug absorption sometimes resulting in low oral bioavailability. It is, therefore, important to know whether poor drug absorption is due to the involvement of specialized secretory transport systems. Modulation of intestinal secretory transport can be a means to enhance absorption of drugs with low oral bioavailability if exsorption of drugs is based on active secretion pathways that are open for control from the "outside".

Protective effects of betamipron on renal toxicity during repeated cisplatin administration in rats and protective mechanism.

The protective effects of betamipron (BP, N-benzoyl-beta-alanine) against nephrotoxicity induced by repeated cisplatin injections were examined. The ratio of the kidney weight to body weight and the lipid peroxide level after treatment with cisplatin plus BP tended to be larger and lower than those after treatment with cisplatin plus alkaline solution, respectively. The blood urea nitrogen, serum creatinine and glutathione levels in the animals treated with cisplatin plus BP differed significantly from those in the animals treated with cisplatin plus alkaline solution. Furthermore, the mechanism of the preventive effects of BP was analyzed for cisplatin-induced nephrotoxicity. The concentration of cisplatin in the renal cortex significantly decreased with concomitant BP. BP inhibited the uptake of cisplatin into the renal cortex in a competitive manner in the same way as an anionic transport inhibitor, probenecid. The treatment with BP appears to be useful for the renal toxicity induced by repeated cisplatin administration.

p53-dependent regulation of MDR1 gene expression causes selective resistance to chemotherapeutic agents.

Loss of functional p53 paradoxically results in either increased or decreased resistance to chemotherapeutic drugs. The inconsistent relationship between p53 status and drug sensitivity may reflect p53's selective regulation of genes important to cytotoxic response of chemotherapeutic agents. We reasoned that the discrepant effects of p53 on chemotherapeutic cytotoxicity is due to p53-dependent regulation of the multidrug resistance gene (MDR1) expression in tumors that normally express MDR1. To test the hypothesis that wild-type p53 regulates the endogenous mdr1 gene we stably introduced a trans-dominant negative (TDN) p53 into rodent H35 hepatoma cells that express P-glycoprotein (Pgp) and have wild-type p53. Levels of Pgp and mdr1a mRNA were markedly elevated in cells expressing TDN p53 and were linked to impaired p53 function (both transactivation and transrepression) in these cells. Enhanced mdr1a gene expression in the TDN p53 cells was not secondary to mdr1 gene amplification and Pgp was functional as demonstrated by the decreased uptake of vinblastine. Cytotoxicity assays revealed that the TDN p53 cell lines were selectively insensitive to Pgp substrates. Sensitivity was restored by the Pgp inhibitor reserpine, demonstrating that only drug retention was the basis for loss of drug sensitivity. Similar findings were evident in human LS180 colon carcinoma cells engineered to overexpress TDN p53. Therefore, the p53 inactivation seen in cancers likely leads to selective resistance to chemotherapeutic agents because of up-regulation of MDR1 expression.

Betamipron reduces cisplatin nephrotoxicity in rodents without modifying its antileukemic activity in mice.

Protective effects of betamipron (BP, N-benzoyl-beta-alanine), one of a series of N-acyl amino acids, on cisplatin-induced nephrotoxicity were examined. Since the damage observed in the kidney is localized to the proximal tubule cells, we investigated the influence of BP on urinary enzymes and excreta. Male Wistar rats and ddY mice were injected i.p. with 6 mg/kg and 16 mg/kg, respectively, of cisplatin combined with an i.p. 250 mg/kg BP dose. The toxicity of cisplatin as indicated by body weight gain, blood urea nitrogen, and serum creatinine levels was significantly (p < 0.05) suppressed by administration of BP after cisplatin treatment. The increase in urinary N-acetyl-beta-D-glucosaminidase activity, increase and subsequent decrease in gamma-glutamyl transferase activities, and increase in beta 2-microglobulin level observed after treatment with cisplatin were suppressed by administration of BP after cisplatin treatment. The combination of cisplatin and BP had no apparent effect on the efficacy of cisplatin against P388 leukemic cells in mice.

Effects of betamipron on cisplatin nephrotoxicity and its pharmacokinetics in rats.

The protective effects of betamipron (BP, N-benzoyl-beta-alanine) on the nephrotoxicity of cisplatin were examined as indicated by body weight gain, ratio of kidney weight to body weight, blood urea nitrogen and serum creatinine levels in tumor-bearing rats. The results showed clearly that administration of BP 1 h after cisplatin treatment affords protection against the nephrotoxicity of cisplatin. Furthermore, the addition of BP to cisplatin had no apparent effect on the efficacy of cisplatin against Walker 256 carcinosarcoma cells in rats. In addition, no observed significant difference in plasma cisplatin concentration between cisplatin with alkaline solution and cisplatin with BP may be partly attributed to the decrease in the cisplatin exsorption to the intestine and its excretion to bile, and to an increase in cisplatin excretion to the urine.

Protective effects of N-benzoyl amino acids on cisplatin nephrotoxicity in rats.

The protective effects of N-benzoyl amino acids (NAAs) and piperacillin (PIP), anionic transport inhibitors, against the nephrotoxicity of cisplatin were examined in rats. Male Wistar rats were injected i.p. with 6 mg/kg of cisplatin combined with i.p. NAAs or PIP. Rats were sacrificed on day 5 after cisplatin injection to weigh the kidney and liver, and to determine blood urea nitrogen (BUN) and serum creatinine (serum Cr) levels. Treatments with NAAs were an effective means of protection against cisplatin-induced nephrotoxicity. The combination of cisplatin with NAAs containing a short and straight chain significantly suppressed (p < 0.05) the changes in body, kidney and liver weights, BUN and serum Cr. Further, betamipron (BP) at a 2000 mg/kg dose showed no apparent effect on the body, kidney and liver weights, BUN and serum Cr levels in rats. The combination of cisplatin with PIP caused a loss in body weight. The protective effects of PIP against cisplatin toxicity are inferior to those of BP when compared at 250 mg/kg doses.

Protective effect of N-benzoyl-beta-alanine against cisplatin nephrotoxicity in rats.

Prophylactic effects of N-benzoyl-beta-alanine (betamipron, BP), one of a series of N-acyl amino acids, were examined against cisplatin-induced nephrotoxicity. Male Wistar rats were injected i.p. with 6 mg/kg of cisplatin combined with an i.p. BP dose given at various times and various doses. Rats were sacrificed 5 days after cisplatin injection to weigh the kidney and liver, and to determine blood urea nitrogen (BUN) and serum creatinine (serum Cr) levels. Preliminary results suggest that treatment with BP is an effective means of protection against cisplatin-induced nephrotoxicity. Combination with BP reduced the weight loss following treatment with cisplatin. The ratios of the kidney and liver weights to the body weight in the animals treated with cisplatin followed later with BP are significantly different (p < 0.05) from those in the animals that received only cisplatin. The BUN and serum Cr levels in the animals treated with cisplatin followed from -1 to 4 hr, and from -4 to 4 hr later with 250 mg/kg BP dose and followed 1 hr later with from 250 to 1000 mg/kg, and from 250 to 2000 mg/kg BP doses differed significantly (p < 0.05) from those in the animals that received only cisplatin. Histological analysis of the kidneys confirmed the protective effect of BP.

Abnormal expression of apoptosis-related antigens, Fas and bcl-2, on circulating T-lymphocyte subsets in primary Sjögren's syndrome.

OBJECTIVE: To clarify the pathological role of the apoptosis-related molecules expressed on peripheral blood (PB) lymphocyte subsets in primary Sjögren's syndrome (SS). METHODS: The levels of apoptosis-regulating proteins, Fas and bcl-2, were determined in the PB lymphocyte subsets from 21 patients with SS and 14 healthy controls by 2-color flow cytometry. RESULTS: In the PB from SS patients, lymphocytopenia, especially CD4+ cell-lymphocytopenia, was prominent. As observed in previous studies, the percentages of CD4+ CD45RA+ cells were lower in the SS patients than in the controls, while activated (DR+) cells were increased in CD4+ cells from the patients. Fas+ cells were also increased in the patients' CD4+ cells and CD8+ cells, but not in their B cells or natural killer cells. Furthermore, we observed several positive correlations among the percentages of activated cells (DR+ cells or CD45RA-cells) and Fas+ cells recognized in the CD4+ and/or CD8+ cells from the patients. On the other hand, intra-cellular bcl-2 proteins measured as mean fluorescence intensity were significantly diminished in the CD4+ cells, CD8+ cells, CD19+ cells, CD45RO+ cells and Fas+ cells from 14 SS patients compared with 12 healthy controls. In addition, the numbers and/or percentages of CD4+ cells and Fas+ cells positively correlated with their expression of bcl-2 in SS patients. CONCLUSION: The abnormal balance between Fas and bcl-2 expression detected in the PB lymphocyte subsets from SS patients relates, at least partially, to the lymphocytopenia observed in the patients.

[Effects of cytarabine ocfosfate on colony-stimulating factor in myelodysplastic syndrome with monosomy 7].

A 42-year-old man was admitted to our hospital because of pancytopenia in April 1992. A diagnosis of refractory anemia was made. The karyotype was normal male type on the initial study. Subcutaneous administration of granulocyte colony-stimulating factor (G-CSF) initially increased the peripheral neutrophil count, bat in January 1993, although blast cells did not increase, neutrophils had decreased in spite of the continuation of G-CSF administration. Chromosome analysis showed 46XY, +Y, -7 at this point. By adding 50 mg of cytarabine ocfosfate (SPAC) daily, the peripheral neutrophil count again rose dramatically. However, anemia, thrombocytopenia and the chromosomal abnormality were unchanged. These results indicate that SPAC may upregulate the effect of G-CSF on granulopoiesis in patients with myelodysplastic syndrome.