Comparison of uptake and binding of disodium cromoglycate and phenol red in rat lung

In rat lung slices 3H-disodium cromoglycate (3H-DSCG) (0.001 mM) was taken up rapidly and 3H-DSCG tissue spaces, which equilibrated by 30 minutes, remained constant over a 4-hour incubation period. In contrast, 35S-phenol red (0.001 mM) accumulated in lung slices to a much greater extent than did DSCG, and the measured tissue spaces continued to increase over a 3-hour incubation period. In the presence of either phenol red (1 mM) or the metabolic inhibitors, iodoacetic acid (10(-4) M) and dinitrophenol (10(-4) M), 3H-DSCG uptake was significantly decreased. Accumulation of 3H-DSCG in lung slices and binding to tissue homogenates (pH 7.4) was also decreased when Ca and Mg ions were omitted from the bathing solution. Although DSCG and phenol red mutually inhibited the accumulation of one another over time in lung slices and 3H-DSCG (0.001 mM) binding to lung homogenates was decreased in the presence of 1 mM phenol red, 35S-phenol red efflux was not altered by the addition of 1 mM DSCG during the washout. Thus, it appears that, in rat lung, DSCG and phenol red share a common binding site(s) for uptake, possible on the transport "carrier." Also, there appear to be additional pulmonary binding sites for phenol red. These sites are not occupied by DSCG and their presence could account for the differences observed in the extent of accumulation of the two compounds in lung slices.

Pharmacokinetics--uses and abuses

It is apparent from studying recent articles on pharmacokinetics that a number of misunderstandings exist, both about the design of experiments and the analysis of results. The purpose of this paper is to outline many of the common pitfalls associated with the design of experiments and also the limitations upon the analysis of results. The paper describes mathematical, laboratory and clinical aspects which must be examined in designing a protocol for pharmacokinetic experiments. Simulated data is presented to demonstrate the dangers of using standard computer programs for parameter estimation. Even when convergence is obtained the answers may be dependent on the method employed. A mathematical model is of little use unless a reasonable amount of good, accurate data is obtained.

The fate of ( 14 C)disodium cromoglycate in man

The fate of [14C]disodium cromoglycate (DSCG) has been examined in 12 asthmatic patients. Maximum plasma concentrations (mean 9.2 ng/ml) were obtained within 15 min of inhaling DSCG (20 mg) and the average plasma half-life was 81 min. Although absorption from the lung is rapid, most of the inhaled dose is swallowed. Only 2.0% of the dose was excreted in the urine, and 84% was recovered from the faeces. DSCG is poorly absorbed from the gastrointestinal tract, only 0.4 % of an oral dose (20 mg) appeared in the 24 h urine and 83 % was recovered from the faeces. Intravenous administration of DSCG resulted in approximately equal amounts (30–50% of dose) being excreted via the urine and faeces. No metabolites of DSCG were detected chromatographically.