No abstract

Theophylline determination in saliva was proposed several years ago as a convenient and non-invasive alternative to monitoring plasma in children and adults. Published data demonstrated that theophylline saliva concentration linearly correlates plasma concentration. However, the variability found in interindividual serum/saliva ratios and the wide scattering among the data points precluded the clinical use of saliva for theophylline monitoring. The purpose of this study was to compare different standardized methods for obtaining stimulated saliva intending to reduce the variability in plasma/saliva ratios and to determine the most reliable one. A group of 150 ambulatory chronic asthmatic 4.5 to 20.83 (10 +/- 3.7; M +/- SD) year-old patients receiving theophylline 6.85 +/- 1.88 mg/kg every 12 h as slow release preparations for 4 to 100 days was studied. One ml venous blood and salivary specimens were simultaneously collected 5.15 +/- 0.36 h after the morning maintenance dose. In a subgroup of 75 patients, saliva was collected using first a new device called salivette, immediately followed by the collection of an expectorated sample 30 s after citric acid crystals stimulation. In the other patients saliva was collected using citric acid containing salivette. Theophylline concentration was determined using HPLC. For all types of saliva collection, salivary and plasma theophylline concentrations correlated significantly. However whichever method was used, based on the -2 to +2 SD interval, a large range of plasma theophylline was predicted from a single salivary theophylline concentration. Despite a further standardization of the sampling of saliva, saliva theophylline could not accurately predict plasma concentration.

Monoamine-based antidepressants can prophylactically protect against stress-induced gastric ulcers. Although the central nucleus of amygdala (CeA) has been shown to modulate the severity of stress ulcers, little is known about the molecular mechanisms underlying the gastroprotective effect of this kind of drugs. Here, we first used proton magnetic resonance spectroscopy, a non-invasive tool, to explore the change of neurometabolites of the CeA of rats pretreated with the duloxetine of selective serotonin-norepinephrine reuptake inhibitors during 6 h of water-immersion restraint stress (WIRS). Duloxetine decreased N-acetyl-aspartate/creatine ratio (NAA/creatine) in CeA after WIRS, which was paralleled by the amelioration of gastric lesions. Meanwhile, the gastric ulcer index was negatively correlated with reduced NAA/creatine. Furthermore, the intra-CeA infusion of NAA aggravated WIRS-induced gastric mucosa damage, which suggested the crucial role of reduced NAA. Western blotting was performed to identify the specific enzymes responsible for the change of the contents of NAA at 0.5 h/3 h/6 h after WIRS, considering the preventative gastric protection of duloxetine. The NAA-catabolizing enzyme aspartoacylase (ASPA) was the only enzyme downregulated by 0.5 h WIRS and upregulated by duloxetine. Moreover, overexpressing ASPA in CeA alleviated stress ulcers. Additionally, all of the other three monoamine-based antidepressants, the fluoxetine of selective serotonin reuptake inhibitors, the amitriptyline of tricyclic agents, and the moclobemide of MAOs, increased ASPA expression in CeA. Together, these results indicate that increasing ASPA to hydrolyze NAA in CeA is a common mechanism of gastroprotective effects against stress exerted by monoamine-based antidepressants, and ASPA is a shared target more than monoamine regulation for this kind of drugs.