Abstract. In this study we have examined the role of voltagegated calcium channels in the regulation of calcium in juxtaglomerular cells. Using a combination of patch-clamp and single-cell calcium measurement we obtained evidence neither for voltage-operated calcium currents nor for changes of the intracellular calcium concentration upon acute depolarizations of the cell membrane. Increases of the extracellular concentration of potassium to 80 mmol/1 depolarized the juxtaglomerular cells close to the potassium equilibrium potential, but did not alter the intracellular calcium concentration neither in patch-clamped nor in intact Furaester-loaded cells. Moreover, basal renin secretion from a preparation enriched in mouse juxtaglomerular cells and from rat glomeruli with attached juxtaglomerular cells was not inliibited when extracellular potassium was isoosmotically increased to 56 mmol/1. In mouse kidney slices, however, depolarizing potassium concentrations caused a delayed inhibition at 56 mmol/1 and a delayed stimulation of renin secretion at 110 mmol/1. Taken together, our study does not provide direct evidence for a role of voltage-activated calcium channels in the regulation of calcium and renin secretion in renal juxtaglomerular cells.

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A novel commercially available ELISA for direct measurement of melatonin concentration in serum was evaluated and compared with an RIA routinely used in our laboratory. The direct ELISA is technically simpler, requires a smaller sample volume (0.1 mL), and compares well with RIA in terms of stability of the calibration curve and intra- and interassay CVs. Correlation with RIA measurements is, however, suboptimal (y = 0.39x + 56; r = 0.65, P < 0.001; n = 138), which may be due to a serum effect, as evidenced by dilution studies. Furthermore, the detection range of the ELISA does not cover the physiological daytime melatonin concentrations in humans. Adding an extraction and 10-fold concentration step shifted the detection range of the ELISA to include low physiological concentrations as well. Correlation with RIA measurements also improved significantly (y = 0.97x-23; r = 0.95, P < 0.001; n = 105), probably due to removal of the serum effect. Although extraction increases the required sample volume (1.5 mL), work load, and procedure time, this step is necessary for the ELISA to compete successfully with RIA.

Sleep quality can be significantly impacted by nasal congestion, a common symptom related to allergic rhinitis (AR). This may lead to decreased learning ability, productivity at work or school, and a reduced quality of life. A number of inflammatory cells and the release of inflammatory mediators lead to increased nasal congestion, causing disrupted sleep and subsequent daytime somnolence. Therefore, it is important to treat AR with medications that improve congestive symptoms without worsening sedation. Second-generation antihistamines and anticholinergic drugs are well tolerated but have little effect on congestion and therefore are limited in their ability to reduce AR-associated daytime somnolence. However, intranasal corticosteroids reduce congestion, improve sleep and sleep problems, and reduce daytime sleepiness, fatigue, and inflammation. Montelukast, a leukotriene receptor antagonist, has joined the approved therapies for AR. Montelukast significantly improves both daytime and nighttime symptoms. AR treatment should endeavor to improve daytime and nighttime symptoms, sleep, and productivity thereby improving quality of life.

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