Therapeutic studies in hyperthyroidism; use of radioactive iodine

Of 112 patients with hyperthyroidism who were treated with radioactive iodine, 110 were relieved of the disease. Nine had transient hypothyroidism. Twelve had permanent hypothyroidism. No other adverse effects that could be attributed to radioactive iodine were noted.     

Acceleration of pentobarbital metabolism in tolerant mice induced by pentobarbital pellet implantation

The time course of inductions of N-demethylation and pentobarbital hydroxylation of hepatic drug metabolizing system in continuous pentobarbital administration by pentobarbital pellet implantation in the mouse is presented. The results also demonstrate that hepatic microsomal drug-metabolizing enzymes in the mouse could be induced much faster by a single pentobarbital pellet implantation than by the ordinary parenteral administration technique. The reduction of pentobarbital half-life ($\text{T}\text{1}\text{2}$) in plasma, brain and liver of the animals which had been implanted with a pentobarbital pellet also substantiates the acceleration of pentobarbital metabolism in the mouse by the pellet implantation method. The results show that the $\text{T}\text{1}\text{2}$ of pentobarbital in plasma, brain and liver of pentobarbital pellet implanted groups is only $\text{1}\text{2}\text{,}\text{1}\text{6}\text{and}\text{1}\text{9}$ of that of the placebo control group, respectively. The studies on urinary excretion of pentobarbital and its metabolites also reveals that pentobarbital pellet implantation induced much faster rate of metabolism of pentobarbital in the mouse.     

The use and limitations of deuterated lorcainide in metabolism and pharmacokinetic studies

Lorcainide, a new antiarrhythmic agent currently undergoing clinical trial, has been pentadeuterated and the usefulness of this labelled compound in pharmacokinetic and metabolism studies has been investigated in dogs. Specific analytical methods based on capillary gas chromatography/mass spectrometry (GC/MS) were developed for quantitative and qualitative analysis of plasma and urine samples. Following oral administration of an equimolar mixture of 5 : 5 mg of (2H0/2H5)lorcainide, eight major metabolites were rapidly identified in urine by the ion cluster technique. Quantitative analysis of (2H0/2H5)lorcainide in plasma and urine indicated an enhanced systematic availability of the deuterated compound, probably due to a secondary isotope effect. According to these findings in the dog, the use of deuterated lorcainide in human bioavailability and metabolism studies is probably of limited value.     

The microbial-mammalian metabolic axis: beyond simple metabolism

The microbiome heavily influences the metabolism of its host. In this issue of Cell Metabolism, Donohoe and colleagues demonstrate that microbial butyrate, used as a fuel metabolite, prevents autophagy in colonocytes, showing that the microbial-mammalian metabolic axis goes beyond simple metabolism.     

The safe use of radioactive isotopes in teaching experiments

Radioisotopes have played major roles in the investigation of biochemistry and physiology and many courses now include some instruction in the practical use of these materials. This article briefly discusses some of the dangers involved in the use of radioisotopes and includes a comprehensive list of precautions and laboratory rules for use during radiobiology experiments.     

Effective use of renal cortical slices in transport and metabolic studies

The uptake and metabolism of two water-soluble vitamins were measured in rat renal cortical slices, isolated tubules, and vesicles of the brush-border and basolateral cell membranes to determine (a) whether it is possible to produce slices that have open tubules and, (b) whether slices and tubules metabolize vitamins similarly. Transport of ascorbic acid is sodium-dependent in slices and in brush-border vesicles but is sodium-independent in basolateral vesicles, suggesting that the brush-border membrane of slices is accessible to components of the bathing solution. Nicotinic acid was metabolized similarly (97-98%) in both slices and isolated tubules. Oxygen consumption by slices maintained in a closed chamber was constant as pO2 decreased from 88% to 58%. Slices are concluded to be a suitable model for transport and metabolic studies providing that care is taken in their preparation and use.     

Effective use of renal cortical slices in transport and metabolic studies

The uptake and metabolism of two water-soluble vitamins were measured in rat renal cortical slices, isolated tubules, and vesicles of the brush-border and basolateral cell membranes to determine (a) whether it is possible to produce slices that have open tubules and, (b) whether slices and tubules metabolize vitamins similarly. Transport of ascorbic acid is sodium-dependent in slices and in brush-border vesicles but is sodium-independent in basolateral vesicles, suggesting that the brush-border membrane of slices is accessible to components of the bathing solution. Nicotinic acid was metabolized similarly (97–98%) in both slices and isolated tubules. Oxygen consumption by slices maintained in a closed chamber was constant as pO₂ decreased from 88% to 58%. Slices are concluded to be a suitable model for transport and metabolic studies providing that care is taken in their preparation and use.