Iodide concentration by the thyroid gland, an essential step for thyroid hormone synthesis, is mediated by the Na + /I symporter (NIS). To identify factors that may regulate this process, we have studied NIS gene expression in the Fisher rat thyroid cell line (FRTL-5) by a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) technique. Increasing concentrations of bovine TSH (0·1, 1, 10, 50 and 100 mU/l), with or without tumour necrosis factor-(TNF ), interferon-(IFN ) or interleukin-1 (IL-1 ) were added to FRTL-5 cells previously deprived of TSH for a minimum of 5 days. RNA was extracted and samples were studied for NIS expression. TSH enhanced NIS mRNA expression in a dose-dependent manner, with induction evident at 0·1 mU/l, reaching a peak at 50 mU/l, an effect detected after 6 h of stimulation, but not in the first 2 h. Both TNF and, to a lesser extent, IL-1 inhibited basal and TSH-induced NIS expression. High concentrations of IFN also downregulated TSH-stimulated NIS mRNA expression.Using the same technique, we also investigated NIS mRNA tissue distribution in two male and one female Wistar rats. High levels of NIS expression were detected in the thyroid, stomach, and mammary gland, lower levels were found in the intestine, adipose tissue and liver, borderline levels were expressed in the salivary gland, and no expression was detected in the kidneys.In summary, we have shown that TSH upregulates rat NIS gene expression in vitro, and this induction can be modulated by cytokines. Analysis of the distribution of rat NIS mRNA ex vivo demonstrated variable levels of NIS transcription in different tissue samples.

The thyroid-stimulating hormone (TSH) binds to a receptor which activates adenylate cyclase and elevates cAMP concentration. In addition, effects of TSH on intracellular calcium and inositol phosphate accumulation have been reported. However, the mechanism of TSH-stimulated accumulation of inositol phosphates and elevation of calcium levels is unresolved. Previous work from this laboratory has shown TSH to cause acute transient increases in intracellular calcium in pig, human and FRTL-5 rat thyroid cells as well as in cells transfected with the human TSH receptor ( JPO9 cells) in some (but not all) experiments. The aim of this study was to investigate the variability of the calcium response to TSH in JPO9 cells to learn more about the nature of this calcium signal induction. Calcium responses to TSH were determined using the fluorochrome fura-2 in both monolayers of adherent cells and adherent single cells. The responses to a single addition and to repetitive additions of TSH were compared. We also determined the cAMP response to TSH using these two protocols of TSH addition.Our data show that, whereas the cAMP response to TSH is highly predictable and consistent and does not require multiple exposures to TSH, cells were unlikely to respond to TSH with an increase in calcium unless they received multiple challenges with the hormone. A single addition of 10 mU/ml TSH failed to increase calcium in any of 40 single cells examined and in only 4 of 15 monolayers of cells (27%) examined; in contrast, 10 of 12 monolayers eventually responded with an increase in calcium after multiple exposure to TSH and 18 of 67 single cells. Similar data were obtained whether calcium was measured in single cells or in populations of cells. We also demonstrated cooperativity between an adenosine derivative, N 6 -(-2-phenylisopropyl)adenosine, and TSH such that their co-administration resulted in a consistent and marked elevation in calcium levels not achieved with either agonist alone. In summary, we suggest that the coupling between the TSH receptor and the intracellular signalling system that leads to activation of intracellular calcium in JPO9 cells requires repetitive stimulation or the influence of other agonists, in contrast with the coupling between the TSH receptor and activation of the adenylate cyclase enzyme.

The transport of iodide into the thyroid, catalyzed by the Na+/I- symporter (NIS), is the initial and rate-limiting step in the formation of thyroid hormones. To study the basic characteristics of the human (h) NIS, we have established a Chinese hamster ovary cell line stably expressing the hNIS (CHO-NIS9). In agreement with previous work on the rat NIS, iodide uptake in these cells was initiated within 2 min of the addition of 131I, reaching a plateau after 30 min. Both perchlorate and thiocyanate inhibited iodide uptake in a dose-dependent manner, with inhibition evident at concentrations of 0.01 and 0.1 micromol/L, respectively, and reaching complete inhibition at 20 micromol/L and 500 micromol/L, respectively. Ouabain, which blocks the activity of the Na+/K+ adenosine triphosphatase, also inhibited iodide uptake in a dose-dependent manner, starting at concentrations of 100 micromol/L and reaching maximum inhibition at 1600 micromol/L, indicating that iodide uptake in these cells is sodium dependent. CHO-NIS9 cells were further used to study 88 sera from patients with Graves' disease, for iodide uptake inhibitory activity, which were compared with sera from 31 controls. Significant iodide uptake inhibition was taken as any inhibition in excess of the mean + 3 SD of the results with the control sera. On this basis, 27 (30.7%) of the Graves' sera, but none of the controls, inhibited iodide uptake in CHO-NIS9. IgGs from these patients also inhibited iodide uptake, indicating that this inhibitory activity was antibody mediated. In summary, we have established a CHO cell line stably expressing the hNIS and shown that antibodies in GD sera can inhibit iodide uptake in these cells. This further emphasizes the role of NIS as a novel autoantigen in thyroid immunity.

No abstract

HE TRANSORAL METHOD for intubat-T ing the trachea in anesthesia is the most direct approach and has given the least traumatic sequelae, primarily because of the satisfactory exposure provided by direct laryngoscopy and the benefit of succinylcholine r e 1 a x a t i o n.Rarely, however, it is necessary to use the blind nasotracheal approach because of anatomic abnormalities or surgical conditions, and sometimes this is the only possible method for instituting general anesthesia safely. At present, this is a technique which is being used less frequently, and anesthesiologists are becoming less facile in its use. Difficulties may develop, therefore, if an anesthesiologist without previous experience with this method must use it as an emergency measure.A review of the many methods described for the blind placement of a nasotracheal tube reveals a common factor-the patient should breathe as rapidly and as deeply as possible. All discussions on this subject indicate that this objective is achieved by carbon di-oxide retention, light planes of anesthesia, or conscious hyperpnea by the patient.'J These observations also show that a swiftly flowing current of air tends to bring an object to the middle of the stream. Modifications of the technique of blind nasotracheal intubation may take advantage of these principles.The easiest and most frequently used method of aspirating tracheal secretions is the passage of a catheter through the nose into the trachea. Surgeons use this method most commonly in the patient who is awake while anesthesiologists use it with equal facility in the unconscious patient. Endoscopists also have found that the nasoesophageal catheter is a useful guide for the passage of the esophagoscope through the cricopharyngeal pinch~ock.~ More commonly, esophagoscopists pass their instruments to the level of the cricopharyngeus. A flexible bougie or catheter is then passed via the esophagoscope through the cricopharyngeal pinchcock causing it to relax. With the bougie as a guide, the scope then is passed over it and into the esophagus with greater ease and safety. Advantage was taken of these principles and observations to s o l v e a difficult problem of tracheal intubation for anesthesia in the following case.A 58-year-old white Italian man was admitted to the Presbyterian Hospital, New York City, for the operative evaluation of obstructive jaundice. His general condition preoperatively was satisfactory and there was no obvious reason to anticipate anesthesia problems. In retrospect, however, several features were present that should have alerted the anesthesiologists for intubation diff iculties. He had an aquiline face with a receding lower jaw. The upper teeth were prominent and p r o t r u d i n g and there was limitation of mandibular motion so that the maximal opening between the incisor teeth did not exceed 1% inches.

No abstract

No abstract

No abstract