Role of deacetylation in the nonlinear pharmacokinetics of sulfamonomethoxine in pigs

Perinatal sulfamonomethoxine exposure influences physiological and behavioral responses and the brain mTOR pathway in mouse offspring

Sulfamonomethoxine (SMM) is widely used in the veterinary field in China. Although some clinical surveys have revealed that sulfonamide antibiotics cause adverse nervous system symptoms, the related mechanisms of maternal SMM exposure on the neurobehavioral development of offspring remain unclear. Here, we investigated the effects of perinatal SMM exposure on the physiological and behavioral responses of pubertal offspring mice and the underlying mechanisms. We randomly allocated pregnant mice into the groups treated with SMM at different doses and the saline-treated groups. Maternal mice were orally administered SMM daily from gestational day 1 to postpartum day 21. On postnatal day (PND) 22, the parameters of growth, endocrine hormones, and brain amino acid composition were assessed, as well as the brain transcript levels of key genes involved in the mammalian target of rapamycin (mTOR) signaling pathway. From PND 50 to 55, a battery of behavioral tests relevant to anxiety and memory were then administered. Analysis of the results indicated that the pups, particularly the pubertal female offspring, showed anxiety-like behavior. Moreover, the pubertal offspring showed cognitive impairments and fat accumulation. Furthermore, the relative mRNA expression of genes involved in the mTOR signaling pathway in females on PND 22 was elevated, whereas the expression of N-methyl-d-aspartate receptor 2B (NR2B) was reduced. Together, the results showed that perinatal SMM exposure perturbs neuroendocrine functions, and further alters gene expression in the mTOR pathway and NR2B gene expression early in life, which may contribute to brain dysfunction in pubertal life.

Determining sulfamonomethoxine and its acetyl/hydroxyl metabolites in chicken plasma under organic solvent-free conditions

A quantitative technique is described for a sample preparation followed by high performance liquid chromatography method for the simultaneous determination of sulfamonomethoxine and its metabolites, N4-acetyl SMM and 2,6-dihydroxy SMM, in chicken plasma. The average recoveries, analytical total time, and limits of quantitation were >/=80% (relative standard deviations (SD) </=6%), <30 min sample-1 (12 samples in 2 h), and </=0.09 microg ml(-1), respectively. The procedure, performed under 100% aqueous conditions, uses no organic solvents and toxic reagents at all and is, therefore, harmless to the environment and humans.

Hepatic biotransformation profiles of sulphamonomethoxine in food-producing animals and rats in vitro

Hydroxylation and acetylation of sulphamonomethoxine (SMM) and deacetylation of N4-acetyl SMM (N4-AcSMM) were estimated in liver post-mitochondrial supernatants (S-9) from laying hens, female cattle, swine and rats. The formation of hydroxylated SMM, 2,6-dihydroxy SMM (2,6-diOH-SMM), was found only with hen S-9s. N4-acetylation rate of SMM was the highest in pig S-9s, followed by rat, then hen or cow S-9s. All S-9s from the four species deacetylated N4-AcSMM. In hen S-9s, the rate of 2,6-dihydroxylation was higher during incubation at 41 degrees C than at 37 degrees C.

Deacetylation as a determinant of sulphonamide pharmacokinetics in pigs

Sulphamonomethoxine (SMM), sulphadimidine (SDD), sulphadiazine (SDZ) and their N4-acetyl derivatives (AcSMM, AcSDD and AcSDZ) were intravenously injected into Goettingen miniature pigs and deacetylation was evaluated from plasma concentration-time curves, renal excretion, and rate constants obtained from pharmacokinetic analysis, using a non-linear least-squares method. Deacetylated metabolite was detected in both plasma and urine after intravenous injection of AcSMM, AcSDD and AcSDZ. The area under the curve (AUC) values for the deacetylated metabolite were significantly higher than those for acetyl derivatives after AcSMM and AcSDD administration, but significantly lower after AcSDZ. After AcSMM and AcSDD injection, the concentration ratio between deacetylated metabolite and acetyl derivative was almost constant in the terminal linear phase and similar to that seen after injection of sulphonamide. After AcSDZ injection, however, a constant ratio was not observed. These results indicate that deacetylation can have a significant effect on the pharmacokinetics of SMM and SDD, but not on those of SDZ in pigs. The rate constant for deacetylation was significantly higher than that for acetylation for SMM and SDD, but significantly lower for SDZ. It is, therefore, concluded that deacetylation may be a determinant of the pharmacokinetics of SMM and SDD in pigs. It was, however, not a determinant of SDZ pharmacokinetics because N4-acetylation is not the main elimination route in pigs.

Simultaneous determination of sulphamonomethoxine and its N4-acetyl metabolite in blood serum by high-performance liquid chromatography with direct injection

A high-performance liquid chromatographic method with direct injection has been developed for the simultaneous determination of sulphamonomethoxine and its N4-acetyl metabolite in serum of animals and fish. A HISEP shielded hydrophobic-phase column (15 cm x 4.6 mm I.D.), a mobile phase of 0.05 M citric acid-0.2 M disodium hydrogenphosphate-acetonitrile (70:15:15, v/v), and ultraviolet detection at 265 nm were used. The standard calibration curves in serum of chicken, pig, cattle, rainbow trout and yellowtail were linear over the range 0.5-20 micrograms/ml. The recoveries of sulphamonomethoxine and its N4-acetyl metabolite from all serum samples determined at different concentrations (0.5, 2.0 and 10.0 micrograms/ml) were 93-103% and 90-103%, respectively. The lowest measurable sulphamonomethoxine and N4-acetyl metabolite concentrations were 0.04 and 0.1 microgram/ml, respectively, for all serum samples.

The role of plasma protein binding on the metabolism and renal excretion of sulphadimethoxine and its metabolite N4-acetylsulphadimethoxine in pigs

The effects of plasma protein binding on the elimination of sulphadimethoxine (SDM) were examined after intravenous administration of 6.25, 12.5, 25, 50, 100 and 150 mg/kg to pigs. At an early stage of the experiment, the animals were anaesthetised by inhalation of enflurane to obtain a more exact relationship between plasma concentration and the renal excretion. SDM and its acetylated conjugate, N4-acetylsulphadimethoxine (N4-SDM) were detected in plasma and urine of all animals, and the recovery of the doses was almost complete in two animals with negligible renal excretion of SDM. The percentages of plasma protein binding of SDM and N4-SDM were almost similar, and ranged from 30 to 95%, depending on the plasma concentration. The metabolic clearance of SDM by acetylation increased when the plasma protein binding decreased. These results suggested that the main elimination route of SDM in pigs is acetylation, and that the plasma protein binding can have a large effect on the elimination of SDM in pigs. The effect of plasma protein binding on the renal clearance of SDM was not so evident, because urine pH had a much greater effect on it. The deacetylation of N4-SDM was detected after 25 mg/kg intravenous administration of N4-SDM, which suggests that the metabolic clearance of SDM is part of an acetylation-deacetylation equilibrium. Saturation of the active tubular reabsorption of SDM and of the active tubular secretion of N4-SDM was also suggested after higher doses of SDM.