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The metabolism and excretion of methylglucamine (N-methyl-D-glucamine) in the rat
Life Sciences Vol . 19, pp . 1925-1928, 1976 . Printed in the II .S .A .
Pergamon Press
THE METABOLISM AND EXCRETION OF METHYLGLUCAMINE (N-METHYL-D-GLUCAMINE) IN THE RAT A .J . Ryan, P .F . Weitzel and G.T . Benness * Department of Pharmacy, University of Sydney, NSW 2006, Australia *Department of Radiology, Flinders Medical Centre, Bedford Park, SA 5042, Australia (Racaiwd in final form November 8, 1976)
Summary Methylglucamine is a commonly used cation in radiocontrast media . The present study sheds light on its fate in the rat . When administered intraperitoneally, 93% of the compound was excreted unchanged in the urine in 24 hr . When administered orally, about 15% of the dose was found in the urine, about 40% in the faeces and 20% in expired air in 24 hr . When administered orally to rats whose gut flora had been depleted by treatment with neomycin sulphate, 19% was excreted in the urine, 69% in the faeces and 3% in expired air in 72 hr . This indicated that the gut flora played a role in the degradation of the compound and its eventual loss as expired carbon dioxide . The use of salts of iodinated organic acids as radiocontrast agents is a common diagnostic procedure . In attempts to alleviate the problems arising frown the large doses of sodium given along with the contrast agents, salts of methylglucamine (N-methyl-Dglucamine) have been increasingly used in intravascular radiography . Also, the methylglucamine salt of diatrizoate is used in gastroenterology especially when there is a suspected gastrointestinal perforation . The presence of a perforation means that the contrast medium may leak into the peritoneum and the use of barium sulphate under such conditions is considered hazardous (2) . Therefore, the metabolism and excretion of methylglucamine followinq both oral and intraperitoneal administration is of interest . Because nothing is known of the fate of methylglucamine in the body, we have studied the excretion of this compound in the rat. The present communication summarises our results . Materials and Methods N-methyl-D-glucamine-14 C uniformly labelled in the glucitol residue (methylglucamine- 14 C) was obtained from the Radiochemical Centre, Amersham . Specific activity was 8 .3 pc/mg and it was at least 98% radiochemically pure by paper and thin layer chromatographY . Male white rats (Wistar derived, 250-330 q) were used throughout . Methylglucamine-14C (150 yg in water) was administered to 5 rats 1925
1926
Methylglucamine Excretion in Rata
Vol .
19, No . 12
orally and to a further 5 rats via the Intraperitoneal route . The animals were individually kept in sealed, all-glass metabolism cages through which a stream of air was passed . The effluent gases were passed through 3 traps containing 20% aqueous NaOH (80 ml) . Urine and faeces were collected for 24 hr . Food and water was available ad lib . One group of 5 rats was given neomycin sulphate (500 mg rat) prior to oral dosing and was then given water containing 1% neomycin sulphate throughout the experiment . The collection period for these animals was 72 hours . Radioactivity was assayed by liquid scintillation counting using an external source standard to determine counting efficiency . Urine was diluted to a known volume with water and 0 .5 ml aliquots counted in Bray's solution (10 ml) (1) . Faeces were dried and powdered and 20 mg aliquots shaken at 60o with methanolic hyamine hydroxide solution (0 .4 ml ; 1 M) for 12 hr . The coloured solution was bleached with a few drops of 30% H202 solution and mixed with Bray's solution (15 ml) for counting . The contents from the alkaline traps were collected and made up to known volume . Aliquots (0 .5 ml) were mixed with Bray's solution (10 ml) and thixotropic gel (300-400 mg ; Cab-O-Sil), shaken and counted after storage in the dark for several hours . Thin layer chromatograms of urine were run on silica coated glass plates with ethyl acetate-acetic acid-methanol-water (15 :3 :3 :2) . The dried chromatograms were divided into 1 cm segments . These were scraped into scintillation counting vials, Bray-'s solution (10 ml) added and counted . RESULTS The excretion of radioactive methylglucamine is summarised in Table I . Intraperitoneal dosing led to rapid and complete excretion . About 93% of the dose was found in the urine, with small amounts in expired air and faeces after 24 hr . Oral dosing showed a different pattern with about 78% of the dose excreted in 24 hr . Urine contained least activity with about 15% of the dose . Expired C02 accounted for 20% and 40% was in the faeces . Neomycin treated animals excreted 91% of the dose in 72 hr, 69% in faeces, 19% in urine and 3% in expired C0 2 . TABLE I Excretion of Radioactivity by Rats after Dosing with Methylglucamine-14C Route of Administration
Urine
% Radioactivity Excreted l Faeces Expired C02
Total
Intraperitoneal
92 .Bt3 .1
3 .4t1 .9
1 .8t0 .5
97 .9t1 .8
Ora1 2
16 .5t5 .9
39 .7t2 .8
20 .1t8 .9
76 .1t6 .3
Ora1 3
19 .1±2 .8
68 .7t4 .7
3 .4±0 .4
91 .1±4 .3
1 Mean ± standard deviation for 5 rats 2 Collected over 24 hours 3 Neomycin treated rats ; collected over 72 hours .
Vol . 19, No . 12
Methylglucamine Eacretion in Rate
1927
Thin layer chromatography of the urine obtained from experimental animals showed unchanged methylglucamine as the only radioactive component . Discussion The results obtained in these experiments clearly show that the fate of methylglucamine is dependent upon the route of administration (Table I) . Parenteral dosing leads to the major amount of the compound being excreted in the urine unchanged . There is some metabolism of the substance as evidenced by the small amount of radioactive C02 expired, as well as minor faecal excretion . This contrasts markedly with oral dosage . Urinary excretion of unchanged methylglucamine accounts for far less of the dose, with the major elimination route being in the faeces . However, some 20~ of the dose was also oxidised to C02 and excreted in the expired air . These results are of considerable interest . The high faecal excretion indicates that methylglucamine is poorly absorbed from the gut after oral dosing . The high excretion of radioactive carbon dioxide in contrast to the parenteral dosage, indicates that the oxidation of methylglucamine occurs mainly in the gut presumably mediated by the gut microflora . Some confirmation of this explanation for the differences in excretion data was obtained after oral dosage of methylglucamine to neomycin treated animals . in this case, where the gut flora has been severely depleted, oxidation of methylglucamine to carbon dioxide was substantially reduced . In this experiment, the collection period was 72 hr instead of 24 hr . .It was found that after 24 hr only about a third of the administered radioactivity was recovered . This was probably due to irregular defaecation by the rats following the neomycin pretreatment and the longer collection period was required to recover a significant fraction of the administered dose . This experiment indicates that the gut flora are largely responsible for the degradation of methylglucamine . The metabolism and excretion of chemically modified sugars has been little studied, Ryan et al . (3) have investigated the fate of hydroxyethylated starch a~fts hydrolysis product 6-hydroxyethylglucose . They concluded that metabolism of this sugar was also largely mediated by the gut flora . As in the present work, no conclusions could be drawn as to the mechanism of the micrological breakdown of the sugar . References 1. 2. 3.
G .A . BRAY, Anal . Biochem . 1 279-285 (1960) . D .C . COCKRAN, C .H . ALMOND ând W .A . SHUCART, Am . J . Roentg . _89 883-887 (1963) . A .J . RYAN, G.M . HOLDER, C . MATE and G .K . ADRINS, Xenobiotica 2 141-146 (1972) .
Pergamon Press
THE METABOLISM AND EXCRETION OF METHYLGLUCAMINE (N-METHYL-D-GLUCAMINE) IN THE RAT A .J . Ryan, P .F . Weitzel and G.T . Benness * Department of Pharmacy, University of Sydney, NSW 2006, Australia *Department of Radiology, Flinders Medical Centre, Bedford Park, SA 5042, Australia (Racaiwd in final form November 8, 1976)
Summary Methylglucamine is a commonly used cation in radiocontrast media . The present study sheds light on its fate in the rat . When administered intraperitoneally, 93% of the compound was excreted unchanged in the urine in 24 hr . When administered orally, about 15% of the dose was found in the urine, about 40% in the faeces and 20% in expired air in 24 hr . When administered orally to rats whose gut flora had been depleted by treatment with neomycin sulphate, 19% was excreted in the urine, 69% in the faeces and 3% in expired air in 72 hr . This indicated that the gut flora played a role in the degradation of the compound and its eventual loss as expired carbon dioxide . The use of salts of iodinated organic acids as radiocontrast agents is a common diagnostic procedure . In attempts to alleviate the problems arising frown the large doses of sodium given along with the contrast agents, salts of methylglucamine (N-methyl-Dglucamine) have been increasingly used in intravascular radiography . Also, the methylglucamine salt of diatrizoate is used in gastroenterology especially when there is a suspected gastrointestinal perforation . The presence of a perforation means that the contrast medium may leak into the peritoneum and the use of barium sulphate under such conditions is considered hazardous (2) . Therefore, the metabolism and excretion of methylglucamine followinq both oral and intraperitoneal administration is of interest . Because nothing is known of the fate of methylglucamine in the body, we have studied the excretion of this compound in the rat. The present communication summarises our results . Materials and Methods N-methyl-D-glucamine-14 C uniformly labelled in the glucitol residue (methylglucamine- 14 C) was obtained from the Radiochemical Centre, Amersham . Specific activity was 8 .3 pc/mg and it was at least 98% radiochemically pure by paper and thin layer chromatographY . Male white rats (Wistar derived, 250-330 q) were used throughout . Methylglucamine-14C (150 yg in water) was administered to 5 rats 1925
1926
Methylglucamine Excretion in Rata
Vol .
19, No . 12
orally and to a further 5 rats via the Intraperitoneal route . The animals were individually kept in sealed, all-glass metabolism cages through which a stream of air was passed . The effluent gases were passed through 3 traps containing 20% aqueous NaOH (80 ml) . Urine and faeces were collected for 24 hr . Food and water was available ad lib . One group of 5 rats was given neomycin sulphate (500 mg rat) prior to oral dosing and was then given water containing 1% neomycin sulphate throughout the experiment . The collection period for these animals was 72 hours . Radioactivity was assayed by liquid scintillation counting using an external source standard to determine counting efficiency . Urine was diluted to a known volume with water and 0 .5 ml aliquots counted in Bray's solution (10 ml) (1) . Faeces were dried and powdered and 20 mg aliquots shaken at 60o with methanolic hyamine hydroxide solution (0 .4 ml ; 1 M) for 12 hr . The coloured solution was bleached with a few drops of 30% H202 solution and mixed with Bray's solution (15 ml) for counting . The contents from the alkaline traps were collected and made up to known volume . Aliquots (0 .5 ml) were mixed with Bray's solution (10 ml) and thixotropic gel (300-400 mg ; Cab-O-Sil), shaken and counted after storage in the dark for several hours . Thin layer chromatograms of urine were run on silica coated glass plates with ethyl acetate-acetic acid-methanol-water (15 :3 :3 :2) . The dried chromatograms were divided into 1 cm segments . These were scraped into scintillation counting vials, Bray-'s solution (10 ml) added and counted . RESULTS The excretion of radioactive methylglucamine is summarised in Table I . Intraperitoneal dosing led to rapid and complete excretion . About 93% of the dose was found in the urine, with small amounts in expired air and faeces after 24 hr . Oral dosing showed a different pattern with about 78% of the dose excreted in 24 hr . Urine contained least activity with about 15% of the dose . Expired C02 accounted for 20% and 40% was in the faeces . Neomycin treated animals excreted 91% of the dose in 72 hr, 69% in faeces, 19% in urine and 3% in expired C0 2 . TABLE I Excretion of Radioactivity by Rats after Dosing with Methylglucamine-14C Route of Administration
Urine
% Radioactivity Excreted l Faeces Expired C02
Total
Intraperitoneal
92 .Bt3 .1
3 .4t1 .9
1 .8t0 .5
97 .9t1 .8
Ora1 2
16 .5t5 .9
39 .7t2 .8
20 .1t8 .9
76 .1t6 .3
Ora1 3
19 .1±2 .8
68 .7t4 .7
3 .4±0 .4
91 .1±4 .3
1 Mean ± standard deviation for 5 rats 2 Collected over 24 hours 3 Neomycin treated rats ; collected over 72 hours .
Vol . 19, No . 12
Methylglucamine Eacretion in Rate
1927
Thin layer chromatography of the urine obtained from experimental animals showed unchanged methylglucamine as the only radioactive component . Discussion The results obtained in these experiments clearly show that the fate of methylglucamine is dependent upon the route of administration (Table I) . Parenteral dosing leads to the major amount of the compound being excreted in the urine unchanged . There is some metabolism of the substance as evidenced by the small amount of radioactive C02 expired, as well as minor faecal excretion . This contrasts markedly with oral dosage . Urinary excretion of unchanged methylglucamine accounts for far less of the dose, with the major elimination route being in the faeces . However, some 20~ of the dose was also oxidised to C02 and excreted in the expired air . These results are of considerable interest . The high faecal excretion indicates that methylglucamine is poorly absorbed from the gut after oral dosing . The high excretion of radioactive carbon dioxide in contrast to the parenteral dosage, indicates that the oxidation of methylglucamine occurs mainly in the gut presumably mediated by the gut microflora . Some confirmation of this explanation for the differences in excretion data was obtained after oral dosage of methylglucamine to neomycin treated animals . in this case, where the gut flora has been severely depleted, oxidation of methylglucamine to carbon dioxide was substantially reduced . In this experiment, the collection period was 72 hr instead of 24 hr . .It was found that after 24 hr only about a third of the administered radioactivity was recovered . This was probably due to irregular defaecation by the rats following the neomycin pretreatment and the longer collection period was required to recover a significant fraction of the administered dose . This experiment indicates that the gut flora are largely responsible for the degradation of methylglucamine . The metabolism and excretion of chemically modified sugars has been little studied, Ryan et al . (3) have investigated the fate of hydroxyethylated starch a~fts hydrolysis product 6-hydroxyethylglucose . They concluded that metabolism of this sugar was also largely mediated by the gut flora . As in the present work, no conclusions could be drawn as to the mechanism of the micrological breakdown of the sugar . References 1. 2. 3.
G .A . BRAY, Anal . Biochem . 1 279-285 (1960) . D .C . COCKRAN, C .H . ALMOND ând W .A . SHUCART, Am . J . Roentg . _89 883-887 (1963) . A .J . RYAN, G.M . HOLDER, C . MATE and G .K . ADRINS, Xenobiotica 2 141-146 (1972) .