Ischemia/reperfusion-induced disruption of rat small intestine transit is reversed by total enteral nutrition

OBJECTIVES

A reduced blood flow to the gut is a consistent event after traumatic shock. Enteral nutrition support has been shown to reduce the septic morbidity after major trauma. We evaluated the effects of a transient ischemia followed by reperfusion (I/R) and an enteral nutrition support regimen on the motility of the small intestine of the rat.

METHODS

A catheter was placed in the upper duodenum and the small intestine was then made ischemic by clamping the superior mesenteric artery for 45 min; the arteries of sham rats were isolated but not clamped. Intestinal transit was evaluated by measuring the amount of fluorescein isothiocyanate-dextran (12 000 MW) in each of 10 intestinal sections at 30 min after injection through the duodenal catheter. The mean geometric center of marker distribution (MGC) was calculated for each group and compared. In a second study, I/R was followed by infusion of saline or a complete nutrient solution overnight, and transit was determined.

RESULTS

Intestinal transit (as the MGC) of I/R rats at 24 h after the beginning of reperfusion (3.5 +/- 0.2) and 48 h after the beginning of reperfusion (4.5 +/- 1.1) was significantly lower than that in the respective sham controls (5.1 +/- 0.3 and 5.9 +/- 0.5). The MGC for rats receiving a nutrient solution overnight during the reperfusion phase (6.0 +/- 1.1) was significantly increased compared with the MGC of 4.8 +/- 0.3 for rats receiving saline during the same period.

CONCLUSIONS

These results demonstrate a long-term deleterious effect of a non-lethal ischemia on intestinal transit and may be one explanation for many of the sequelae occurring after ischemia. In addition, these results demonstrate that a nutrient infusion will prevent the delayed transit. This may provide a partial explanation for the beneficial effects of total enteral nutrition in the clinical situation of posttraumatic injury.

Influence of the ward colon tumor on the innate and endotoxin-induced inflammatory response of the rat

Cachexia, a depressed immune function, and an increased infection rate are recurring problems for cancer patients; the response of the host to an infection may also be increased. We have reported that the transplantable Ward colon tumor (WCT) enhanced the lethality of endotoxin (lipopolysaccharide [LPS]) to the host. The mechanism of this increased LPS lethality and the effect of the presence of the WCT on the host inflammatory response, however, have not been reported. The effect of a transplantable WCT on the innate and endotoxin-induced inflammatory response of rats was, therefore, investigated. The innate inflammatory response was investigated in two ways. First, the formation of a granuloma around a sterile string implanted subcutaneously for 6 days was determined. Second, the effect of tumor presence on the trafficking of leukocytes to a sponge implanted subcutaneously for 2 or 6 days was determined. The tumor decreased the foreign body granuloma formation around a sterile string. The presence of the WCT also significantly blunted the increase of lymphocytes that migrated to the sponge area at 6 days. There was no significant effect of the WCT, however, on the migration of neutrophils, monocytes, or eosinophils to the implanted sponge. The leukocyte distribution of the peripheral blood was not affected by the presence of the WCT or implantation of a sterile string or sponge. To determine the effect of the presence of the WCT on the response of the host to an infection, rats were given LPS (5 mg/kg, i.p.) and the alanine amino transferase (ALT) of plasma and inducible isoforms of nitric oxide synthase (NOS2) protein content of liver, spleen, and terminal ileum was determined. The LPS challenge resulted in an increase in plasma ALT concentrations and NOS2 protein content of liver and spleen, but not the terminal ileum of WCT rats. This elevation in WCT rats confirms that the enhanced LPS-related toxicity in WCT rats was related to an increased liver toxicity. The increased toxicity may be related to an increase in the nitric oxide synthesis of the liver. These results suggest that the WCT, and possibly other tumors, will reduce the ability of the host to respond to a foreign body. If this were an infection, the host would be more likely to succumb to the resulting inflammatory mediators. Further evaluations of the lymphocyte subsets and cytokines in the sponge exudate will be required to completely understand this response.

Organ heavy-metal accumulation during parenteral nutrition is associated with pathologic abnormalities in rats

OBJECTIVES

Metabolic bone disease, hepatic abnormalities, splenic insufficiency, and nephropathy have been associated with long-term total parenteral nutrition (TPN). We determined the heavy-metal contamination in TPN solutions and investigated whether it was associated with organ deposition and pathologic organ damage.

METHODS

Five representative TPN solutions (two adult standard solutions, one renal solution, and one standard pediatric solution to reflect clinical practice) and 28 TPN components were analyzed with inductively coupled plasma mass spectrometry. Twenty-six male Fisher 344 rats were assigned to two groups (chow/NaCl = 8 and TPN = 18). TPN or NaCl was infused at a rate of 50 mL/d. After 14 d, serum, femurs, spine, liver, kidneys, brain, spleen, and testes were analyzed for heavy-metal deposition by using inductively coupled plasma mass spectrometry. Tissues were fixed in formalin, sectioned, and stained with hematoxylin and eosin, periodic acid Schiff, and Masson's trichrome stain. Kidneys were fixed in gluteraldehyde for ultrastructural examination with scanning electron microscopy.

RESULTS

The predominant sources of contaminants in TPN were amino acids (Al, As, Cr, Ge, Pb, Sn), dextrose (As, Ba, Cr, Sn), Ca gluconate (Al), K2PO4 (Al), lipid emulsion (As, Sn), and vitamins (As). Significant variations in the level of contamination depended on TPN formulation and brand of constituents. In the kidney, Pb, Cr, and Mn concentrations were greater than in controls, although there was no correlation with serum creatinine. Hepatic Cr and Pb concentrations were greater in TPN rats, although there was no correlation with serum aspartate aminotransferase or total bilirubin. Splenic Ba, Cr, Ge, Pb, Mn, and Sn concentrations were greater in TPN rats. Only serum Cr concentration was significantly correlated with splenic concentration (r = 0.46, P = 0.04). Brain and serum Ba concentrations were significantly correlated (r = 0.60, P = 0.007). No significant correlations were observed between any other metal in serum and that metal's respective organ concentration. No increase in heavy-metal accumulation was seen in the femur, spine, or testis. There were no significant depositions of As, Cd, Hg, St, or V in any of the organs examined. Serum Al and Cr concentrations were significantly increased in TPN rats, although there was no correlation with tissue concentrations. No significant increases in heavy-metal concentrations in tissue or plasma were observed for any of the other metals measurable by inductively coupled plasma mass spectrometry. Histologically in the TPN group, 50% of the rats had mild to moderate hepatic steatosis and 33% to 50% developed renal morphologic abnormalities; brains and spleens remained histologically normal.

CONCLUSIONS

We found significant heavy-metal contamination of TPN solutions, and this contamination can lead to organ deposition and subsequent histologic abnormalities.

Effect of ornithine in parenteral nutrition regimens on difluoromethylornithine-induced platelet suppression and changes in tumor polyamine content

We have demonstrated that DFMO-induced thrombocytopenia can be ameliorated with concomitant ornithine (Orn) in chow-fed rats; a reversal in DFMO-associated tumor polyamine reduction and antitumor activity, however, was also evident. To determine the effect of Orn in total parenteral nutrition (TPN) regimens on DFMO-induced thrombocytopenia and changes in tumor polyamine concentrations, Ward-colon-tumor-bearing (WCT) rats were given TPN with arginine (ENA) or with ornithine substituted for arginine (ENO) alone or with DFMO (1.5 g/day) added directly to the infusate. After 4 days, the peripheral blood platelet counts for ENA (917 +/- 151 x 10(3)/mm3) or ENO (908 +/- 67 x 10(3)/mm3) were equivalent to those of chow fed rats (901 +/- 42 x 10(3)/mm3). ENA/DFMO rats had significant thrombocytopenia (607 +/- 185 x 10(3)/mm3), which was completely ameliorated for ENO/DFMO rats (939 +/- 111 x 10(3)/mm3). Peripheral white blood count, hematocrit, and other hematological parameters were not affected. Tumor putrescine content for ENA rats (46.9 +/- 8.7 nmol/g) was equal to that for chow-fed rats (44.8 +/- 6.2 nmol/g) and ENO rats (53.6 +/- 8.3 nmol/g). The reduction in tumor putrescine content for ENO/DFMO rats (19.6 +/- 6.9 nmol/g) was equivalent to that of ENA/DFMO rats (14.7 +/- 3.0 nmol/g). Tumor spermidine was reduced only for the ENA/DFMO rats while spermine was slightly elevated. Tumor spermine content for ENO/DFMO rats (57.2 +/- 12.0 nmol/g) was equal to that for ENO rats (65.6 +/- 8.7 nmol/g) but was significantly (p = 0.004) reduced when compared with rats receiving ENA/DFMO (89.4 +/- 20.4 nmol/g). The results of this study show that TPN with Orn substituted for arginine can be used with a chemotherapeutic dose of DFMO to ameliorate the thrombocytopenia. The DFMO-induced reduction in tumor putrescine content, however, was not affected when Orn was substituted for arginine in a parenteral nutrition regimen. These results suggest that the antitumor activity of DFMO would not be adversely affected by coadministering DFMO with a TPN regimen with Orn substituted for arginine.

Influence of the Ward colon tumor on the host response to endotoxin

Cachexia and a decreased immune function are negative prognostic factors for cancer patients. While the decreased immunity results in a greater susceptibility to bacterial infection, the response of the host to the resulting infection is not clear. The experiments reported here were designed to evaluate the toxicity of endotoxin to rats with a transplantable Ward colon tumor (WCT) and to evaluate the mechanism of the observed increase in lethal toxicity. The lethal toxicity of endotoxin (lipopolysaccharide, LPS) at 5 mg/kg, i.p. was evaluated in the first of two experiments. Rats received LPS and were observed for morbidity and weight loss for a period of 11 days. A second experiment was done to evaluate the effect of LPS on the plasma nitrate/nitrite concentrations and plasma indicators of host tissue dysfunction. LPS was administered as previously described but blood and tissues were collected 5 h after LPS administration. LPS resulted in the death of 1 of 12 nontumor-bearing (NTB) rats and a transient weight loss in the survivors. This same dose of LPS, however, resulted in death for 10 of 12 WCT rats with tumor burdens less than 4% of body weight. The response of WCT rats 5 h after LPS was then compared with that of age-matched NTB rats. Plasma albumin concentrations were not affected by LPS in NTB rats but were significantly decreased in WCT rats. Peripheral blood gases were not consistently affected by LPS in either group. Peripheral blood white cell counts, except monocytes, were significantly decreased by LPS in both groups. Monocyte counts in peripheral blood were further reduced in WCT rats compared with NTB rats receiving LPS. The presence of the WCT significantly enhanced the LPS-associated increase in spleen weight. Liver weights were lower in LPS rats but there was no effect of the presence of WCT. The LPS-associated increase in plasma nitrate/nitrite concentration was enhanced by the WCT. The plasma arginine and citrulline concentrations were altered in a manner consistent with an increase in nitric oxide synthesis. An increase in plasma ornithine concentration suggests an increase in arginine metabolism by arginase. The plasma concentration of alanine aminotransferase was significantly elevated when WCT rats received LPS, suggesting enhanced hepatic dysfunction. The plasma blood urea nitrogen concentration was elevated by LPS to a greater extent in the WCT rats than in the NTB controls, indicating increased renal dysfunction. These results demonstrate that the Ward colon tumor increases the host lethal response to the endotoxin, a toxic product of bacterial infections. The mechanisms of lethality may include an increased nitric oxide synthesis in WCT rats and enhanced liver and renal toxicity.

Temporal expression of tumor necrosis factor-alpha and nitric oxide synthase 2 in rat small intestine after endotoxin

Temporal changes in tumor necrosis factor-alpha (TNF-alpha) and nitric oxide synthase 2 (NOS 2) were evaluated in segments of duodenum, jejunum, and ileum removed from male Sprague-Dawley rats 30, 60, 120, 180, and 240 min after lipopolysaccharide (LPS), 5 mg/kg, intraperitoneally. Plasma was assayed for TNF-alpha and for nitrate/nitrite (NOx). Intestinal and plasma TNF-alpha were elevated by 60 min after LPS and were back to control levels by 180 min. For control rats, NOS 2 was detected in the ileum, but not in the duodenum or the jejunum. In rats treated with LPS, NOS 2 was detected in all areas of the intestine at 120 min and was greatest at 240 min. Plasma NOx was elevated at 120 min and continued to increase to 240 min. The time course of changes in intestinal TNF-alpha and NOS 2 were similar to those reported for other tissues and suggest that the early and late actions of the LPS on the intestine may involve both mediators.

A parenteral nutrition regimen with ornithine substituted for arginine alters the amino acid, but not polyamine, content of the ward colon tumor

Substituting ornithine for arginine in total parenteral nutrition (TPN) regimens eliminates the TPN-enhanced growth of the Ward colon tumor. Plasma arginine was increased when tumor growth was increased, suggesting a role for this amino acid. The erythrocyte polyamine content, however, was elevated in rats receiving both TPN regimens, indicating an increased synthesis and availability for tumors receiving arginine- and ornithine-containing regimens. The objective of this study, therefore, was to evaluate the effect of substituting ornithine for arginine in a TPN regimen on the amino acid and polyamine content of the Ward colon tumor compared with that of rats fed chow ad libitum. Male Fischer 344 rats with a transplantable Ward colon tumor implanted subcutaneously were randomized to three groups and fed for four days. One group received a TPN regimen with arginine (1,300 mg/100 ml, ENA), whereas a second group received a regimen with an isonitrogenous substitution of ornithine (ENO). A control group received chow ad libitum. Serum and tumors were evaluated for arginine, ornithine, lysine, and polyamine content. The arginine concentration in the serum and tumor increased when rats received ENA. In contrast, the serum and tumor arginine content for rats receiving ENO was significantly lower than that for rats receiving chow or ENA. Tumor and serum ornithine content was increased severalfold when ornithine was included in the regimen. Tumor polyamine content was not affected by TPN. The results show that serum and tumor arginine content are significantly altered by substituting ornithine for arginine in a TPN regimen. These and previous results suggest that TPN-enhanced growth of the Ward colon tumor when arginine is included in the formulation occurs by a mechanism other than increased polyamine synthesis.

Reduced tissue ornithine increases the cytotoxicity of difluoromethylornithine

BACKGROUND

Polyamines are low molecular weight cations that are essential for the growth of all cells. The polyamine inhibitor difluoromethylornithine (DFMO) will decrease tumor growth when administered parenterally; thrombocytopenia is the major dose-limiting toxicity. Since an essential amino acid-based total parenteral nutrition (TPN) regimen was shown to reduce the ornithine and polyamine content of a transplantable sarcoma in preliminary studies, the effect of the amino acid content of TPN on the antitumor activity of DFMO was evaluated.

MATERIALS AND METHODS

Fischer 344 male rats were inoculated subcutaneously with a transplantable sarcoma and fed a restricted intake of Purina rodent chow-5001 (8 g/d, RI) for 12 days to induce malnutrition. Rats were then randomized to continue receiving the RI regimen or to receive one of two TPN regimens for an additional 6 days. Isocaloric TPN was formulated with essential amino acids (E) as the sole nitrogen source or with E and nonessential amino acids including arginine (ENA). DFMO (1000 mg/kg/d) was added to the infusate of one group of rats receiving each of the respective TPN regimens.

RESULTS

The growth rate of the sarcoma was significantly decreased (P < 0.05) when DFMO was administered with E for 6 days but not when given to rats receiving ENA. DFMO-related thrombocytopenia was greater when administered with E as compared with rats given ENA. The plasma and tissue levels of DFMO were not affected by the TPN amino acid content nor did DFMO have any effect on plasma or tissue ornithine levels. The plasma and tissue levels of ornithine, however, were significantly lower for rats given E as compared with rats receiving ENA or those continued on RI.

CONCLUSIONS

The results show that the cytotoxicity of DFMO was enhanced by an essential amino acid-based TPN. This increase was directly associated with a decrease in the plasma and tissue content of ornithine and polyamines.

Nutritional support for adaptation to radiation-induced suppression of mucosal immunity in the intestine of the rat

Appropriate enteral nutrition provided immediately after injury or trauma to the gastrointestinal tract may limit or reverse damage to the mucosal barrier. In this regard, diets containing amino acids, such as arginine and glutamine, or fish oil have been identified as beneficial. This report assesses the role of amino acids as "essential nutrients" in the repair of intestinal mucosa damaged by gamma radiation. Rats were used experimentally to test the hypothesis that the recovery of the immune responses in the intestinal mucosa, which are suppressed by radiation, can be improved by feeding an elemental amino acid diet, referred to hereafter as the diet, immediately after irradiation. The objective was to assess the impact of the diet on the expression of type I hypersensitivity or anaphylaxis in the jejunal mucosa. The local expression of this immunological response, which involves several radiosensitive cell types, was studied in rats immunized by oral infection with the nematode parasite, Trichinella spiralis. Rats that recover from infection become immunized and their small intestine undergoes anaphylaxis when subsequently challenged with parasite-derived antigen. This hypersensitivity response is expressed, in part, as Cl- secretion and can be observed in vitro or in vivo. When challenge is provided by a secondary inoculum of infective T. spiralis larvae, Cl- secretion is accompanied by fluid secretion and by the rapid expulsion of the parasite from the intestine. Immunized rats maintained on a stock diet and exposed to 7 Gy of total-abdominal irradiation from a cobalt-60 gamma-ray source failed to express antigen-induced Cl- secretion fully for up to 14 days postirradiation, and rejection of the parasite was suppressed for at least 30 days postirradiation. The suppression of immune responsiveness is associated with the disappearance of intestinal mucosal mast cells, which normally trigger the anaphylactic response. When rats are maintained on the diet after irradiation, the capacity to reject the parasite remains suppressed. However, the ability to express anaphylaxis-mediated Cl- secretion returns by 3 days postirradiation. The quick, diet-supported recovery of antigen-induced Cl- secretion occurs despite the continued absence of mast cells. Although the recovery of anaphylaxis-mediated responses suppressed by irradiation is only partial, our experimental results underscore the potential for enhancing the recovery process through nutritional support.

Citrulline and arginine increase the growth of the Ward colon tumor in parenterally fed rats

Arginine is considered a necessary component of parenteral regimens because of the high nitrogen intake. The effect of arginine on tumor growth, however, is controversial. Our results suggest that substituting ornithine for arginine in parenteral regimens will ameliorate an arginine-related increase in growth of a Ward colon tumor. Although a metabolite of arginine and ornithine in the urea cycle, citrulline has differential effects on growth in vivo and in vitro. To evaluate the effect of citrulline on tumor growth, Ward colon tumor-bearing rats were given parenteral nutrition regimens with ornithine (ENO) or citrulline (ENC) substituted for arginine (ENA). The plasma amino acid profiles and tumor growth were compared. Tumor growth was evaluated by changes in the calculated tumor weight over an eight-day feeding period. The initial tumor weight for all groups was equivalent. The final tumor weights of rats receiving ENA (14.1 +/- 3.3 g) and ENC (12.7 +/- 1.4 g) were significantly (p < 0.05) greater than those of rats receiving ENO (8.8 +/- 2.0 g) or the chow-fed controls (8.9 +/- 2.1 g). Plasma concentrations of arginine, ornithine, and citrulline were significantly increased when the respective amino acids were components of the regimen. The plasma arginine concentration of rats receiving ENO (60.4 +/- 3.8 microM) was significantly lower than the control (149.9 +/- 24.1 microM). The plasma arginine concentration was significantly increased for rats receiving ENA (280.3 +/- 68.1 microM) and was even further increased for rats receiving ENC (481.8 +/- 94.1 microM). The plasma glutamine concentration for ENO rats (536.4 +/- 37.5 microM) was significantly higher than that for controls (483.5 +/- 53.5 microM). The plasma glutamine concentration for rats receiving ENA (402.3 +/- 50.3 microM) and ENC (379.9 +/- 37.6 microM) was significantly lower than that of the control fed chow. These results further implicate arginine as a major factor for the total parenteral nutrition-enhanced growth of the Ward colon tumor.

Effect of intralipid infusion on serum high- and low-density lipoprotein cholesterol, lecithin:cholesterol acyltransferase, and lipoprotein lipase in tumor-bearing rats

We compared the effects of 0.45% normal saline (NS), 5% Intralipid (IL), and 16.7% glucose (Glu) infusions on total serum triglycerides and cholesterol, serum high-(HDL-c) and low-density lipoprotein cholesterol (LDL-c), and activity of serum lecithin:cholesterol acyltransferase (LCAT), and serum lipoprotein lipase (LPL) in rats implanted with a fibrosarcoma. In tumor-bearing rats given NS, a two-fold increase in total serum cholesterol, a four-fold increase in LDL-c, and a five-fold decrease in the HDL-c/LDL-c ratio were observed compared to tumor-free rats. In tumor-bearing rats administered IL, a two-fold increase in total serum triglyceride and cholesterol, a three-fold increase in HDL-c and HDL-c/LDL-c ratio, and a two-fold increase in LPL activity were observed compared to tumor-bearing rats administered NS. In tumor-bearing rats administered Glu, a two-fold decrease in total serum cholesterol, a two-fold decrease in HDL-c, and a three-fold decrease in LDL-c were observed compared to tumor-bearing rats administered NS. Tumor weights and LCAT activity did not differ significantly between treatment groups. Previous results have demonstrated that lipophilic compounds that interact with plasma lipoproteins have altered pharmacological effects when administered with IL. Therefore, this study suggests that IL infusions alter the HDL-c/LDL-c ratio and could affect the pharmacological behavior of anticancer compounds that predominantly distribute into the LDL fraction upon entrance into the bloodstream.

Concentrations in serum and distribution in tissue of free and liposomal amphotericin B in rats during continuous intralipid infusion

The influences of Intralipid (IL) and 0.45% normal-saline infusions on the concentration in serum and distribution in tissue of amphotericin B (AmpB) and liposomal amphotericin B (L-AmpB) in rats were compared. In animals receiving a continuous IL infusion, concentrations of AmpB in kidneys and lungs were significantly higher, but the concentration of AmpB in serum was significantly lower in animals administered AmpB versus those given L-AmpB. In animals receiving a continuous normal-saline infusion concentrations of AmpB in kidneys and the spleen were significantly higher, but the concentration of AmpB in serum was significantly lower in animals administered AmpB versus those given L-AmpB. These results suggest that the increased total serum cholesterol and high-density lipoprotein cholesterol during the IL infusion decreased the clearance of AmpB from the bloodstream and decreased the L-AmpB concentration in the kidney and lung.

Effects of intralipid infusion on rat serum lipoproteins

The purpose of this investigation was to study the effects of continuous Intralipid infusions on serum HDL and LDL levels in the rat. Male Fischer 344 rats were infused continuously via central venous catheter with 10% Intralipid for 96 h and 5, or 2.5% Intralipid for 14 days. Blood samples were collected during the infusion period for total serum cholesterol, HDL-, and LDL-cholesterol measurements. Food intake was monitored during the studies. Total cholesterol, HDL-cholesterol and LDL-cholesterol levels were significantly elevated following 96 h of infusion with 10% Intralipid with food intake significantly decreased compared to a control group. In a second experiment, animals received a continuous infusion of either 5% Intralipid, 2.5% Intralipid or 0.45% saline for 14 days. Total cholesterol, HDL-cholesterol and LDL-cholesterol were significantly elevated following 14 days of infusion with 5% Intralipid group compared to controls but food intake remained constant for 12 days with no evident toxicity.

Glutamine stability in biological tissues evaluated by fluorometric analysis

Although glutamine has been considered unstable during storage and therefore difficult to quantitate, recent results suggest this amino acid is stable at low pH ranges. We evaluated the stability of glutamine in plasma and tissue extracts, using fluorometric analysis. The measured concentration of glutamine detected varied linearly up to 0.8 mmol/L for the aqueous solution (r2 = 98.7, P = 0.0001) with a mean (+/- SD) coefficient of variation of 2.41% +/- 0.79%. When glutamine was dissolved in 50 g/L trichloroacetic acid (TCA), the values were essentially unaltered. Glutamine in an aqueous solution and stored at -70 degrees C was stable for at least 16 days; glutamine in TCA was stable for 6-8 days, then decreased to a concentration significantly lower than that of the aqueous solution. The expected and observed concentrations in plasma were equal (r2 = 0.99975) for increasing amounts of added glutamine. Glutamine concentrations in plasma were stable for > 1 year when stored at -70 degrees C. The glutamine of a transplantable rat sarcoma and a normal rat liver could be extracted with 50 g/L TCA with high efficiency (88.6% +/- 1.9% and 90.2% +/- 0.04%, respectively); the extracted glutamine is stable in TCA for at least 7 days without neutralization when stored at -70 degrees C. Fluorometric analysis of glutamine required only a small quantity of plasma (25 microL) or tissue (200 mg) and is a convenient method for quantifying this important amino acid.

Glutamine stability in biological tissues evaluated by fluorometric analysis

Although glutamine has been considered unstable during storage and therefore difficult to quantitate, recent results suggest this amino acid is stable at low pH ranges. We evaluated the stability of glutamine in plasma and tissue extracts, using fluorometric analysis. The measured concentration of glutamine detected varied linearly up to 0.8 mmol/L for the aqueous solution (r2 = 98.7, P = 0.0001) with a mean (+/- SD) coefficient of variation of 2.41% +/- 0.79%. When glutamine was dissolved in 50 g/L trichloroacetic acid (TCA), the values were essentially unaltered. Glutamine in an aqueous solution and stored at -70 degrees C was stable for at least 16 days; glutamine in TCA was stable for 6-8 days, then decreased to a concentration significantly lower than that of the aqueous solution. The expected and observed concentrations in plasma were equal (r2 = 0.99975) for increasing amounts of added glutamine. Glutamine concentrations in plasma were stable for &gt; 1 year when stored at -70 degrees C. The glutamine of a transplantable rat sarcoma and a normal rat liver could be extracted with 50 g/L TCA with high efficiency (88.6% +/- 1.9% and 90.2% +/- 0.04%, respectively); the extracted glutamine is stable in TCA for at least 7 days without neutralization when stored at -70 degrees C. Fluorometric analysis of glutamine required only a small quantity of plasma (25 microL) or tissue (200 mg) and is a convenient method for quantifying this important amino acid.

Substituting ornithine for arginine in total parenteral nutrition eliminates enhanced tumor growth

Total parenteral nutrition (TPN) may enhance the growth of some tumors: this enhanced growth is associated with an increase in the erythrocyte polyamine levels. The effect of arginine in TPN on tumor growth was compared with ornithine using rats with a transplantable Ward colon tumor. The relationship of circulating arginine, ornithine, glutamine, and polyamines with tumor growth was investigated. For rats fed chow ad libitum, increasing tumor weights were associated with a linear decrease in the plasma arginine levels which was consistently lower than that of age-matched non-tumor bearing (NTB) rats; ornithine and lysine levels were not affected. Subsequent experiments suggest that plasma glutamine levels were also lower in tumor bearing rats. Pair-fed NTB rats had reduced arginine but not glutamine levels in plasma. TPN regimens with arginine or with ornithine substituted for arginine at two levels (equimolar [Orn-Em] or isonitrogenous [Orn-IN]) were given to colon tumor bearing rats for 8 days. The final tumor weight of rats which received the arginine-containing regimen (19.8 +/- 5.7 g, n = 4) (P less than 0.05) was significantly greater than the tumor weight of rats fed chow ad libitum (12.1 +/- 3.3 g, n = 6). The final tumor weights of Orn-EM (11.2 +/- 2.6 g, n = 4) or Orn-IN (11.6 +/- 0.8 g, n = 6) were similar to the chow-fed controls. The plasma arginine levels were elevated, compared with the control, when arginine was present in the regimen. The plasma arginine levels of rats which received Orn-EM or Orn-IN were lower than the controls. The plasma ornithine levels were not affected by arginine in the regimen but were elevated with increasing levels of ornithine in TPN. Plasma glutamine levels were decreased when arginine was present in the regimen but were elevated when ornithine was substituted for arginine. Erythrocyte putrescine was increased when either arginine or ornithine was included in the TPN regimens. These results demonstrate that while arginine in a parenteral regimen stimulates tumor growth, substituting ornithine for arginine in TPN does not enhance the growth of a transplantable colon tumor.

Amelioration of thrombocytopenia with concomitant ornithine in sarcoma-bearing rats receiving high dose difluoromethylornithine

The dose limiting toxicity of difluoromethylornithine (DFMO), when administered by continuous infusion, is thrombocytopenia. DFMO-induced antitumor activity and thrombocytopenia were time- and dose-dependent up to 1700 mg/kg/d when administered continuously for 12 days. Concomitant ornithine administration (at selected molar ratios to DFMO) ameliorated thrombocytopenia induced by DFMO at a dose of 2000 mg/kg/day without adversely affecting its antitumor activity. The purpose of this study was to determine if ornithine could ameliorate the thrombocytopenia of higher DFMO doses and increase the efficacy of DFMO. Fischer 344 male rats with a transplantable sarcoma in the right flank were given 2000 and 3500 mg/kg/d DFMO alone or with ornithine at a molar ratio of 0.4 for 8 days by continuous infusion. Concomitant ornithine infusion overcame the thrombocytopenia that was induced by either dose of DFMO without reducing the antitumor activity against the sarcoma. The antitumor activity, tumor polyamine levels, and tumor S-adenosylmethionine decarboxylase activity did not consistently change with increasing doses of DFMO or with the addition of ornithine to the infusion regimen. These results demonstrate that the thrombocytopenia induced by doses of DFMO greater than 2000 mg/kg/d can be ameliorated without compromising the antitumor activity.

Colorectal ornithine decarboxylase activity in human mucosa and tumors: elevation of enzymatic activity in distal mucosa

To examine the value of ornithine decarboxylase (ODC) assay as a biological marker of potential malignancy in large bowel, we harvested 43 colorectal carcinoma, 7 adenoma, 6 polyps, and 77 normal-appearing mucosa at surgery from patients with colorectal carcinoma. In addition, 13 normal rectal mucosa were obtained at biopsy from patients with benign diseases or diseases unrelated to colorectal carcinoma as normal control. ODC activity was significantly higher in polyps and adenocarcinomas than in normal-appearing mucosa from patients with colorectal carcinoma. ODC activity in normal-appearing mucosa varied throughout the large intestine, with significantly higher activities in the distal segment of the large bowel. The higher ODC activity detected in the sigmoid colon and rectum correlates with the larger incidence of tumor development in this region of the large bowel. This observation needs to be taken into consideration when ODC activities of the colorectal mucosa are measured as biological markers of potential malignancies.

Evaluation of continuous-infusion alpha-difluoromethylornithine therapy for colorectal carcinoma

A total of 32 evaluable patients with measurable advanced colorectal carcinoma were treated with continuous-infusion alpha-difluoromethylornithine (DFMO) at a median daily dose of 8 g/m2 (range, 6-14 g/m2). DFMO was infused over 24 h daily for 28 days, followed by a rest period of 7 days. Of the 32 patients, 14 had received no prior chemotherapy. A total of 65 courses was given, with the median being 2 (range, 1-9 courses). None of the patients achieved a partial or complete response; however, 3 patients achieved a minor response and 14 had stable disease. The frequent toxic effects of DFMO included thrombocytopenia (which was dose-limiting), malaise, nausea, vomiting, reversible hearing loss, and diarrhea. Our data suggest that continuous-infusion DFMO therapy is feasible and results in only mild gastrointestinal toxicity. Although DFMO proved to be ineffective as a single agent in this trial, it could probably best be used in combination with cytotoxic agents known to enhance its antitumor activity in a preclinical setting.

Differential effects of parenteral nutrition on tumor growth and erythrocyte polyamine levels in the rat

The influence of total parenteral nutrition (TPN) on tumor growth and erythrocyte polyamine levels was evaluated in rats with a transplantable fibrosarcoma or a Ward colon tumor. During the experimental periods the fibrosarcoma grows exponentially when rats are fed chow ad libitum while the colon tumor reaches a plateau of its Gompertzian growth curve. A 12-day regimen of TPN resulted in an increased growth of the colon tumor but not the fibrosarcoma. The erythrocyte putrescine levels of fibrosarcoma-bearing rats and the levels of putrescine, spermidine, and spermine of Ward colon-tumor-bearing rats were significantly increased by TPN compared with similarly treated nontumor-bearing (NTB) rats. When the growth of the fibrosarcoma was slowed by feeding a restricted intake (RI) regimen, a subsequent 6-day regimen of TPN resulted in increased tumor growth. Erythrocyte polyamine levels of fibrosarcoma-bearing, RI-rats were elevated by TPN repletion. There was a consistent, significant, interaction between TPN and tumor presence on the erythrocyte putrescine levels in fibrosarcoma-bearing rats and the levels of all polyamines in Ward colon-tumor-bearing rats. The effects of TPN on tumor growth and erythrocyte polyamine levels of tumor-bearing rats may be dependent on the growth characteristics of the tumor. The data demonstrate that TPN consistently enhanced the tumor contribution to the erythrocyte putrescine pool.

Alterations in polyamine metabolism during continuous intravenous infusion of alpha-difluoromethylornithine showing correlation of thrombocytopenia with alpha-difluoromethylornithine plasma levels

Polyamine biosynthesis is important for cell proliferation and growth. The purpose of this study was to determine the biochemical and pharmacological parameters associated with host toxicity from a continuous infusion of alpha-difluoromethylornithine (DFMO). Twenty-five patients with metastatic carcinoma of the colon or rectum received continuous infusion of DFMO at a median dose of 8 g/m2/day (range, 6-14) for 28 days. DFMO plasma levels, RBC, plasma putrescine, spermidine, and spermine levels, and patient toxicities were evaluated. There was a significant decrease in RBC and plasma levels of putrescine, spermidine, and spermine following DFMO administration compared with the baseline RBC and plasma levels. Pearson correlation coefficient comparing nadir platelet count and steady-state DFMO level was statistically significant (n = 37; P less than 0.01; r = -0.53). Sustained suppression of circulating polyamine levels was also achieved with continuous DFMO infusion. The correlation between steady-state plasma DFMO levels and lowering of platelet count warrants prospective evaluation to determine its clinical usefulness.

Reduction of difluoromethylornithine-induced thrombocytopenia in rats with ornithine while maintaining antitumor activity

The purpose of this study was to evaluate the effect of a concomitant infusion of ornithine on the difluoromethylornithine (DFMO)-induced thrombocytopenia and antitumor activity. Male Fischer 344 rats with either a transplantable fibrosarcoma or Ward colon tumor were given a 12-day continuous infusion of DFMO (2000 mg/kg/day) alone or with ornithine. The dose of ornithine was defined as the molar ratio to DFMO. A continuous infusion of DFMO significantly reduced circulating platelet counts to 5-16% of the control. Concomitant ornithine treatment at a molar ratio of 0.2-0.5 resulted in protection of the rat from thrombocytopenia while the antiproliferative activity of DFMO against the fibrosarcoma or Ward colon tumor was unaffected. At a higher ornithine: DFMO molar ratio (0.7), the DFMO-induced inhibition of tumor growth was blocked. Tissue polyamine levels suggest a different sensitivity of tumor and normal tissue to DFMO. Concomitant ornithine resulted in a greater increase in the polyamine levels of normal tissues, compared with the tumor. These results suggest that ornithine can selectively inhibit DFMO-induced thrombocytopenia while not affecting the antitumor activity.

Polyamine-directed preferential nutritional repletion of normal tissues in tumor-bearing hosts

Our previous study demonstrated that total parenteral nutrition (TPN) increases erythrocyte (RBC) polyamines selectively in cancer patients but not in non-cancer patients, suggesting that these changes may relate to tumor presence. We therefore studied the possible relationship between RBC polyamine levels and potential tumor growth induced by TPN. In addition, we attempted to control tumor growth during TPN with alpha-difluoromethylornithine (DFMO), a suicide inhibitor of ornithine decarboxylase (ODC), in a fibrosarcoma-bearing rat model. Rats in a control group received chow ad libitum for 3 weeks and their tumors grew exponentially. A restricted intake (RI) tumor-bearing group received 8 g chow per day per rat; this produced malnourished rats in which tumor growth significantly slowed. The third group (RI----TPN) received the RI diet for 2 weeks and TPN for 1 week, which resulted in an increase in tumor growth. The last group (RI----TPN + DFMO) received a 2-week RI regimen and 1-week TPN plus DFMO regimen, which inhibited tumor growth to the level of the RI group due to the addition of DFMO (1 g/kg/day). Although the addition of TPN to the RI regimen markedly increased tumor ODC activity, as well as tumor putrescine and RBC putrescine levels, the addition of DFMO to the RI----TPN regimen entirely abolished these increases. Despite DFMO treatment, liver ODC activity in RI----TPN + DFMO group was unaffected. The plasma albumin level, an indicator of host nutrition, of the RI----TPN + DFMO group was significantly higher than that of the RI group. Liver, spleen, kidney and total body weights of the RI----TPN or RI----TPN + DFMO group were significantly higher than those of the RI group. These results indicate that TPN can enhance tumor growth in malnourished hosts and that the addition of DFMO to TPN can effectively control this TPN-enhanced tumor growth, leading to preferential nutritional repletion of the host.

Influence of total parenteral nutrition on tumor growth and polyamine biosynthesis of fibrosarcoma-bearing rats after induced cachexia

The effect of a protein-free diet (PF) or a restricted intake of chow (RI) and subsequent host repletion with total parenteral nutrition (PF-TPN, RI-TPN) on tumor growth and polyamine metabolism of fibrosarcoma-bearing rats was examined. Host weight was significantly reduced by PF and RI. Tumor growth was reduced in malnourished rats with the PF regimen resulting in the greatest decrease. Rats receiving TPN after 14 days of the RI or PF regimens had higher host weight and plasma albumin levels than malnourished rats. Tumor growth during TPN was evaluated as the percent increase and compared with that of the respective malnourished rats. The percent increase for RI-TPN rats was significantly greater although a trend toward an increase was also evident for PF-TPN rats. Tumor ornithine decarboxylase (ODC) activity and putrescine levels were increased for PF rats and decreased for RI rats while tumor ODC activity was consistently increased by TPN. Tumor growth, ODC activity, and putrescine levels were simultaneously increased only for those rats fed the RI regimen prior to TPN. These results show a disparity in tumor ODC activity, putrescine levels, and tumor growth in malnourished rats. The results of this study suggest that the nutritional origin of cachexia influences the response of the tumor to TPN and emphasizes the importance of considering the methods to induce malnutrition in designing therapuetic regimens.

Polyamine metabolism in carcinoma of the oral cavity compared with adjacent and normal oral mucosa

In this study, polyamine biosynthesis required for cellular proliferation showed elevated levels in neoplastic cells. Putrescine, spermidine, and spermine, as well as the rate-limiting enzyme ornithine decarboxylase, were measured to evaluate differences in tissue concentration in squamous cell carcinoma of the oral cavity, and in the normal adjacent, buccal, and retromolar trigone tissues. Mean polyamine levels (nanomoles per gram of tissue +/- standard error of the mean) were significantly elevated in tumor tissue at 136 +/- 42 nmol/g for putrescine compared with 41 +/- 9 nmol/g in adjacent, 25 +/- 5 nmol/g in buccal, and 41 +/- 14 nmol/g in retromolar trigone tissues. Tumor spermidine was 415 +/- 41 nmol/g compared with 192 +/- 34 nmol/g in adjacent, 184 +/- 34 nmol/g in buccal, and 214 +/- 63 nmol/g in retromolar trigone tissues. Tumor spermine was 461 +/- 41 nmol/g compared with 236 +/- 30 nmol/g in adjacent, 233 +/- 35 nmol/g in buccal, and 269 +/- 59 nmol/g in retromolar trigone samples. Ornithine decarboxylase activity was highly variable in tumor tissues. High levels of polyamines appear to be specific for this malignancy, whereas ornithine decarboxylase activity is not. Measurement of polyamine content may be useful in evaluating epithelial changes in the oral cavity.

Effect of intravenous alpha-difluoromethylornithine on the polyamine levels of normal tissue and a transplantable fibrosarcoma

The effect of a continuous i.v. infusion of alpha-difluoromethylornithine (DFMO) on the polyamine metabolism of tumor and normal host tissue was determined. Non-tumor-bearing Fischer 344 rats or rats bearing a transplantable fibrosarcoma received continuous infusions of DFMO through a central venous catheter at three dose levels. Treatment with DFMO resulted in a time- and dose-dependent, cytostatic effect on the growth of the tumor. In fibrosarcoma-bearing rats the tumor putrescine levels were reduced after 6 and 12 days of DFMO treatment. Tumor spermidine levels were consistently reduced after 6 and 12 days of treatment with the reduction being dose dependent. The decrease in tumor ornithine decarboxylase activity was dose dependent. Erythrocyte putrescine levels were decreased in tumor- and non-tumor-bearing rats, suggesting that DFMO reduces the tumor contribution to the erythrocyte pool. Erythrocyte spermidine levels of fibrosarcoma- and non-tumor-bearing rats were elevated at the lower DFMO doses administered for 12 days but returned to normal as the dose was increased. Erythrocyte spermine levels were elevated in both groups of rats at all DFMO doses. Although normal host tissue weights were not affected by treatment with DFMO, the putrescine and spermidine levels of liver, spleen, and kidney and ornithine decarboxylase activity of the liver and kidney were decreased. These data demonstrate that i.v. DFMO has a cytostatic effect toward a rapidly growing fibrosarcoma associated with the depletion of both tumor putrescine and spermidine levels.

Red blood cell polyamine levels and host toxicity during continuous alpha-difluoromethylornithine infusion

The dose effects of continuous alpha-difluoromethylornithine (DFMO) infusion on red blood cell (RBC) polyamine levels, host toxicity and tumor growth were determined. Male rats with and without a transplantable methylcholanthrene-induced sarcoma received intravenously either 0.45% NaCl or DFMO at 500 mg, 1,000 mg, or 2,000 mg/kg body wt/day for 6 or 12 days. Dose-related inhibition of tumor growth was noted after the 12-day treatment. There were no changes in host carcass weight, food intake, plasma albumin, hematocrit or white blood cell counts. Platelet suppression was associated with the 1,000- and 2,000-mg doses with the 12-day treatment. Morphometry of the small intestine revealed mild but significant shortening of villi in the duodenum and jejunum at the 2,000-mg dose, but none of the animals developed diarrhea. The 500-mg DFMO dose reduced the rate of tumor growth without inducing platelet suppression or altering intestinal morphology. A decrease in RBC putrescine levels was noted at all doses. RBC spermidine levels increased with the 500-mg dose. RBC spermine levels were higher at all doses compared with controls. These results suggest that thrombocytopenia is the major dose-limiting side-effect of continuous DFMO infusion but does not occur at a dose of 500 mg/kg body wt/day.

Relationship of erythrocyte polyamine levels and growth rate of transplantable tumors in rats

Varying levels of polyamines in the urine, plasma, and erythrocytes (RBC) of cancer patients have been demonstrated. The growth rate of the tumor has been suggested as a primary factor which determines whether the polyamine levels in urine are elevated. To further evaluate tumor size and growth rate as variables affecting polyamine levels in physiological fluids, the effect of a transplantable fibrosarcoma and colon tumor on the RBC polyamine levels of Fischer 344 rats was determined. The tumors were implanted s.c. and grew without metastasis or spontaneous regression. The fibrosarcoma grew exponentially up to a weight of approximately 69 +/- 15 (SD) g and was associated with a linear increase in RBC polyamine levels compared with that of non-tumor-bearing rats. RBC putrescine, spermidine, and spermine levels were significantly elevated at tumor weights of 12.5 +/- 1.4, 20.4 +/- 3.8, and 33.2 +/- 5.0 g, respectively. The respective polyamines increased consistently thereafter until the tumor weight was 57.8 +/- 5.8 g. In contrast with the fibrosarcoma, the colon tumor grew exponentially only to a weight of 9.2 +/- 4.7 g, at which time the growth rate of the tumor began to decrease (time T of the Gompertz model). RBC polyamine levels of rats with the colon tumor showed only a transient increase. RBC putrescine levels were significantly increased at a tumor weight of 12.9 +/- 1.2 g and spermidine at a tumor weight of 17.4 +/- 0.2 g. RBC spermine levels were significantly elevated at both tumor weights; thereafter, all RBC polyamine levels returned to normal. Host cachexia was evident when the fibrosarcoma and colon tumors weighed 12.5 +/- 0.9 and 7.2 +/- 2.6 g, respectively. The polyamine levels of the fibrosarcoma differed significantly from that of the colon tumor. These levels, however, did not correlate with the exponential growth rates. The results suggest that the tumor is the major source of elevated RBC polyamines. The data also suggest that the tumors must be rapidly growing for the elevation in polyamines to occur. This may partly explain why patients with extensive neoplastic disease that may have surpassed time T in the Gompertz model do not manifest abnormal polyamine levels.

Effect of difluoromethylornithine on host and tumor polyamine metabolism during total parenteral nutrition

Clinical and experimental data suggest that erythrocyte (RBC) polyamine (PA) levels are markers of tumor proliferation during total parenteral nutrition (TPN). The purpose of this experiment was to determine whether the inhibition of PA synthesis during TPN was greater in tumors than in normal host tissue. Rats bearing a subcutaneous fibrosarcoma were randomized to receive a chow diet (n = 5), TPN (n = 5), or TPN + difluoromethylornithine (DFMO) (an irreversible inhibitor of ornithine decarboxylase (ODC), at 1000 mg/kg body wt/day n = 4) for 6 days by continuous central venous infusion. TPN + DFMO resulted in a higher plasma albumin level and lower tumor ODC activity compared with chow feeding or TPN. Liver ODC activity was similar for the chow fed, TPN, and TPN + DFMO groups. RBC putrescine, tumor putrescine, and tumor spermidine levels were significantly lower in the TPN + DFMO group compared with the chow fed and TPN groups. RBC spermidine, RBC spermine, and tumor spermine levels were significantly increased with TPN + DFMO compared with TPN alone. DFMO did not produce diarrhea or weight loss. Increased RBC spermidine may indicate a toxic effect of DFMO on the tumor, resulting in leakage of tumor spermidine into the extracellular space. The data suggest that DFMO during TPN can selectively inhibit tumor PA synthesis and may improve host utilization of nutrients.

Nutritional parameters affecting erythrocyte polyamine levels in cancer patients

Changes in erythrocyte polyamine levels during intravenous hyperalimentation in cancer and noncancer patients were determined, and the influence of host nutritional status on polyamine metabolism was analyzed. RBC putrescine (P less than .001), spermidine (P less than .01), and spermine (P less than .005) levels, and the putrescine-spermidine ratio (P less than .001) increased in the cancer group while no significant increases were noted in the noncancer group. The degree of malnutrition, based on body weight loss and plasma albumin, transferrin, prealbumin, and retinol-binding protein levels, was significantly greater in the cancer group than in the noncancer group, giving rise to the possibility that repletion of nutritional deficits in host tissues could have contributed to the rise in RBC polyamines. When cancer patients of similar nutritional status were matched with the noncancer group, increases in RBC putrescine level and putrescine-spermidine ratio were noted in the selected cancer patients. These results suggest that correction of nutritional deficits did not contribute significantly to the RBC polyamine pool and that increases in RBC polyamines during intravenous hyperalimentation were related to the presence of tumor.

Effect of thymidine on the toxicity and antitumor activity of cis-diamminedichloroplatinum (II)

The effect of thymidine (TdR) on the preclinical toxicity of cis-diamminedichloroplatinum (II) (DDP) was investigated in the BDF1 mouse and the Sprague-Dawley rat. The effect of TdR on the antitumor activity of DDP was investigated using the ascites P388 murine leukemia model. TdR at 500 mg/kg consistently decreased the recovery of body weight after DDP treatment IP, but did not affect the lethal toxicity of DDP to non-tumor-bearing mice or those with the P388 murine leukemia. This effect was greatest when TdR was injected 30 min prior to DDP and at higher doses of DDP. A 500-mg/kg dose of TdR did not affect the antitumor activity of DDP 5 mg/kg administered on days 1, 5, and 9. Treatment of rats with TdR 500 mg/kg according to various schedules of timing relative to a 5-mg/kg dose of DDP did not consistently affect the DDP-related loss in body weight or nephrotoxicity at day 3. Pretreatment of mice with TdR 1,500 mg/kg 30 min prior to DDP 5 mg/kg (every 4 days X 3) resulted in a slower recovery of body weight, which became more pronounced with increasing doses of DDP. Pretreatment of ascites P388-bearing mice with TdR 1,500 mg/kg increased the number of early deaths when mice were treated with DDP 5 mg/kg (days 1, 5, and 9). These data suggest that the cytotoxicity of DDP is increased by TdR only at higher doses of either drug, but that the antitumor activity against P388 murine leukemia is not affected.

Modification of polycarbonate cages for individual housing of mice

Polycarbonate cages were modified with clear plastic dividers so that up to four mice could be housed individually in one cage with ad libitum access to feed and water. The method used commercially available components and was applicable for use in any study when it was necessary to keep mice separate for an extended period of time.

Effect of nutritional status on the hepatobiliary excretion of methotrexate in the rat

The effect of induced protein-calorie malnutrition (PCM) and its subsequent nutritional repletion with chow or total parenteral alimentation (TPA) on the hepatobiliary excretion of methotrexate (MTX) was determined in the Sprague-Dawley rat. Compared with full-fed controls, PCM resulted in a decrease in body and liver weight, bile flow, and the cumulative excretion of MTX but a consistently higher plasma MTX concentration at each time-point measured. Repletion with chow and TPA resulted in a gain in body weight and an increase in liver weight. Chow repletion resulted in an increase in bile flow and biliary excretion of MTX equal to that for the controls. Repletion with chow also resulted in a consistently lower plasma MTX concentration as compared with PCM rats. Repletion of PCM via TPA did not affect biliary, or plasma, MTX concentrations although the cumulative biliary excretion of MTX was further decreased. The biliary clearance of MTX was decreased by PCM. The clearance for rats repleted with chow, however, was greater than that for the controls. The clearance for PCM rats repleted via TPA was equal to that for PCM rats but less than that for the controls. When expressed as a function of liver weight and compared with PCM rats, the clearance for rats repleted with chow was increased while that for malnourished rats repleted parenterally was decreased. These studies suggest that the biliary excretion of MTX in the rat is a carrier-mediated process that is sensitive to the nutritional status of the host and independent of the effect of nutritional status on liver weight.

Combination chemotherapy with cyclophosphamide and ftorafur against advanced L1210 murine leukemia

The antitumor activity of cyclophosphamide (CP) in combination with ftorafur (FT) against advanced L1210 murine leukemia was investigated and compared with the activity of the combination of CP and 5-FU. CP at doses of 200--350 mg/kg was highly active, the most effective dose (% treated/control = 327) being 300 mg/kg. The activity of FT up to the LD10 dose and of 5-FU at 50 mg/kg was minimal (% treated/control less than or equal to 142). Coadministration of 200 mg/kg of FT with 100 mg/kg of CP resulted in an increase in activity as compared with the respective dose of CP alone as did the coadministration of 400 mg/kg of FT with 200 mg/kg of CP; the activities, however, were no better than that resulting from treatment with 300 mg/kg of CP alone. The coadministration of CP and 600 mg/kg of FT resulted in an increase in host toxic reactions and loss of antitumor activity, as did the coadministration of 400 mg/kg of FT with 300 mg/kg of CP. Treatment with FT at 400 or 600 mg/kg 24 hours before or after administration of CP at 200 or 300 mg/kg did not increase the activity over that occurring when the respective combinations of the drugs were coadministered. The activity of the combination of CP with 5-FU at doses previously reported to be synergistic was equal to that observed when mice were treated with 300 mg/kg of CP alone. These data suggest that FT increases the cytotoxicity of CP but that the combination is not synergistic.

Effect of malnutrition on methotrexate toxicity and tissue levels of dihydrofolate reductase in the rat

The effect of malnutrition on the toxicity of methotrexate (MTX) and the dihydrofolate reductase (DHFR) content of the liver, small intestinal mucosa, kidney, and bone marrow of male Sprague-Dawley rats was studied. Malnutrition was induced by reducing the daily intake of chow to one third for 14 days. A single ip treatment with MTX was lethal to three of nine rats at a dose of 37.5 mg/kg and to three of five rats at a dose of 50.0 mg/kg but caused only transient weight loss to similarly treated full-fed, age-matched controls. Although the body weights and absolute tissue weights were reduced in malnourished rats, only the liver and small intestinal mucosa were smaller relative to their respective body weights. The cellular DHFR content of liver and bone marrow from malnourished rats was lower than that from the controls, although in terms of the content per gram of tissue, there was no significant change. While the total DHFR in malnourished rat tissues was significantly lower than that for the controls, only the total-liver DHFR was lower relative to the body weight. The increased toxicity of MTX to malnourished rats may be related to the DHFR levels in the liver and bone marrow.

Effect of thymidine on the toxicity and antitumor activity of ftorafur

The effects of thymidine (TdR) on the toxicity and antitumor activity of ftorafur (FT), a 5-FU analog, were determined. The LD10 of FT was 130, 430, and 680 mg/kg, respectively, when FT was administered ip in the following treatment schedules: (a) daily for 9 days, (b) every 4th day for three treatments, and (c) 1 day only. When FT was administered simultaneously with 250 mg/kg of TdR, the LD10 was 13, 62, and 630 mg/kg in the respective treatment schedules. Lethargy was observed in mice when the daily dose of FT was greater than or equal to 150 mg/kg. FT alone was active (% treated/control [T/C] = 153) against ascites P388 murine leukemia only at high, single doses. Simultaneous administration of FT and 250 mg/kg of TdR at or below the LD10 dose of FT resulted in an increase in the antitumor activity to a % T/C of 217 (daily, Days 1-9) and 188 (daily, Days 1, 5, and 9). The activity of FT administered simultaneously with TdR on Day 1 only (%T/C = 142) was lower than that for FT alone. Using a treatment schedule of Days 1, 5, and 9, a TdR/FT mol ratio of greater than or equal to 2.0 seems necessary to achieve an increase in therapeutic value against P388 murine leukemia. This may explain the lack of increase in activity against P388 when 250 mg/kg of TdR was coadministered with FT on Day 1 only. FT alone or coadministered with 250 mg/kg of TdR was equally active against L1210 ascites tumor at doses up to the LD10 with daily treatments on Days 1, 5, and 9 and on Days 1-9; the doses of FT, however, were below those which cause lethargy.