Long-term regulation of proximal tubule acid–base transporter abundance by angiotensin II

In the proximal tubule, angiotensin II (Ang-II) regulates HCO−3 reabsorption and H+ secretion by binding the type 1 Ang-II (AT1) receptor, stimulating Na+/HCO−3 cotransport and Na+/H+ exchange. Studies were carried out to determine if long-term changes in Ang-II receptor occupation alter the abundance of the basolateral Na+/HCO−3 cotransporter (NBC1) or the apical membrane type 3Na+/H+ exchanger (NHE3). In the first set of experiments, rats eating a low-sodium diet were infused with the AT1 blocker, candesartan, or vehicle. In the second, lisinopril-infused rats were infused with either Ang II or vehicle. Transporter abundances were determined in whole kidney homogenates (WKH) and in brush border membrane (BBM) preparations by semiquantitative immunoblotting. Tissue distribution of transporters was assessed by immunocytochemistry. Blockade of the AT1 receptor by candesartan caused decreased abundance of NBC1 in WKH (59±9% of control; P<0.05) and Ang-II infusion increased abundance (130±7% of control; P<0.05). Changes in NBC1 in response to candesartan were confirmed immunohistochemically. Neither candesartan nor Ang II infusion affected the abundance of NHE3 in WKH or cortical homogenates. Candesartan decreased type 2 sodium-phosphate cotransporter abundance in both WKH (52±7% of control; P<0.05) and BBM (32±7% of control; P<0.05). Serum bicarbonate was decreased by candesartan and increased by Ang-II. Candesartan also decreased urinary ammonium excretion (P<0.05). The long-term effects of Ang-II in the proximal tubule may be mediated in part by regulation of NBC1 abundance, modifying bicarbonate reabsorption

Analysis of autoionization resonances in the Hg 6s2-photoionization by measurements of photoelectron polarization

Schäfers F, Schönhense G, Heinzmann U. Analysis of autoionization resonances in the Hg 6s2-photoionization by measurements of photoelectron polarization. Zeitschrift für Physik A: Hadrons and Nuclei. 1982;304(1):41-48.Measurements of the spin polarization of photoelectrons in the autoionization region of the Hg 6s2-subshell using circularly polarized synchrotron radiation and using unpolarized light from rare gas discharge lamps are reported. The results obtained show a pronounced structure across the resonances. Together with data of the cross section and its angular distribution these data from a complete parameter set for the determination of the transition matrix elements and the phase difference of the continuum wavefunctions. Evidences for strong configuration interaction and channel mixing between the open and closed channels were found. The matrix elements and their ratio vary strongly across the resonances and the relative phase shows some changes of sign. A change of the relative phase by Pi across an autoionization resonance, predicted by Fano, has been verified experimentally for the triplet resonance. We would like to express our gratitude to Professors W. Paul, G. Nöldeke and J. Kessler for their continued interest and encouragement. We thank Dr. D. Husmann, Dr. J. Hormes and B. Osterheld for their assistance in performing the experiment in Bonn. We are grateful to Dr. N.A. Cherepkov for helpful discussions and acknowledge support by the DFG and BMFT

Experimental characterization of the Xe 5p photoionization by angle- and spin-resolved photoelectron spectroscopy

Heckenkamp C, Schäfers F, Schönhense G, Heinzmann U. Experimental characterization of the Xe 5p photoionization by angle- and spin-resolved photoelectron spectroscopy. Zeitschrift für Physik D: Atoms, Molecules and Clusters. 1986;2(4):257-274.Spin- and angle-resolved photoelectron spectroscopy with elliptically polarized radiation has been used to fully characterize the dynamics of photoelectron emission from free Xe atoms in the 5p-autoionization and continuum region. An advantageous reaction geometry and its experimental realization at the storage ring BESSY are discussed. The three independent experimental parameters which characterize the angular dependence of the photoelectron spin-polarization vector are reported for the wavelength range from 100nm to 40 nm. The results are compared with theoretical predictions based on RRPA-, RPAE- and semiempirical MQDT-calculations. The combination of existing data for the differential photoionization cross section with the spinpolarization parameters is used to completely decouple the photoionization channels: The transition matrix elements and their relative phases are determined separately for every single dissociation channel. The results are discussed in the context of the MQDT. Correlation effects and the influence of spin-orbit interaction on the continuum states most clearly show up when the Dill-Fano angular-momentum-transfer formalism is applied