1 The human recombinant a 1a -adrenoceptor (AR) has been stably expressed in Chinese hamster ovary cells. Four stable clones, aH4, aH5, aH6 and aH7, expressing 30, 370, 940 and 2900 fmol AR mg 71 protein, respectively, have been employed to characterize this AR subtype using radioligand binding and microphysiometry to measure extracellular acidi®cation rates. 2 Noradrenaline (NA) gave concentration-dependent responses in microphysiometry with increasing extracellular acidi®cation rates. The potency of NA increased as the receptor density increased; pEC 50 values of NA for the clones aH4, aH5, aH6 and aH7 were 6.9, 7.5, 7.8 and 8.1, respectively. This increase of potency according to receptor density indicates the presence of spare receptor for NA. Methoxamine, phenylephrine, oxymetazoline and clonidine also gave concentration-dependent responses with various intrinsic activities. 3 Antagonists shifted concentration-response curves for NA rightward in a concentrationdependent manner. Schild analysis revealed that the anity pro®le of this AR subtype to antagonists in the clone aH7 had a typical pattern for the a 1a -AR; high anity for prazosin and WB 4101, and low anity for BMY7378 (pA 2 =9.5, 9.8 and 7.3, respectively). This pro®le is similar in the case of the clone aH4. These anities were in good agreement with those obtained in binding experiments. 4 These results have demonstrated that (1) classical receptor theory can be applied in microphysiometry, and (2) microphysiometry is a useful tool to investigate the pharmacological characterization of a 1a -AR.

Manual-injection DSA is the largest contributor to radiation exposure received by the interventional radiologist, therefore, the use of a power injector is always recommended when performing DSA. When manual-injection DSA is necessary, radiologists should position themselves as far away from the patient as possible.

This newly proposed method could be a simple and practical way to automatically reduce misregistration artifacts in DSA.

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