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The sensitivity of the Ca2+ pumping ATPase of bovine cardiac sarcolemma (SL) to changes in membrane potential was studied in a preparation of sealed SL vesicles. Membrane potential was imposed by preincubating the vesicles in media of defined ion composition (K+, Cl-, choline+ and gluconate-) and diluting into media of differing ion composition. The durations of the ion gradients and relative ion permeabilities were determined in separate experiments by the dependence of the half time for net K+ (or choline+) movement coupled with these anions (Cl- or gluconate-), registered by the fluorescence of 1-anilino-8-naphthalene sulfonate (Chiu, V.C.K., Haynes, D.H. 1980. J. Membrane Biol. 56:203-218). Relative permeabilities were: 1.0, K+; greater than or equal to 10.0, 1 microM valinomycin-K+; 4.0, Cl-; 0.66, choline+; 0.38, gluconate-. Durations of the gradients ranged between 17 sec (KCl, valinomycin) to 195 sec (K(+)-gluconate-). In separate experiments, active Ca2+ uptake was monitored using chlorotetracycline (CTC) fluorescence, a technique validated by 45-Ca2+ measurements (Dixon, D., Brandt, N., Haynes, D.H. 1984. J. Biol. Chem. 259:13737-13741). Active Ca2+ uptake was initiated in the presence of monovalent ion gradients. The values of the membrane potentials (Em) imposed by the monovalent ion gradients were calculated using the ion concentrations, their relative permeabilities and the Goldman-Hodgkin-Katz equation. No effect of membrane potential on transport rate was observed (less than or equal to 4%, for 5-7% SD) for imposed potentials as extreme as greater than or equal to +71 and less than or equal to -67 mV. Formal analysis shows that the above observations are not compatible with models in which the Ca2+ pumping ATPase functions in an electrogenic or charge-uncompensated fashion. Further experimentation showed that the pump rate is slowed when uptake is measured at less-than-adequate concentrations of buffer (5 vs. 25 mM HEPES/Tris). This, together with further control experiments using nigericin and FCCP, gave evidence that the pump requires a source of counter-transportable H+ in the vesicle lumen. The above experimentation also underlines the need for control of internal pH to obviate erroneous interpretation of ion perturbation experiments. The results are compared with results obtained with the Ca2+ ATPase pump of skeletal sarcoplasmic reticulum.

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To assess the medium-term performance of the Uretex Urethral Support System, patients were evaluated by the 1-h pad test, cough stress test (CST), Valsalva leak-point pressure test (VLPP), and validated questionnaires. Seventy-five patients were enrolled; median follow-up was 3.6 years (range, 3.1-4.3 years). All patients had a negative CST, 65 (87%) had no leakage during VLPP, and 62 of 72 patients (86%) had a negative 1-h pad test. Compared with baseline values of 50.0 and 28.6, median Urogenital Distress Inventory and Incontinence Impact Questionnaire-7 scores at 3-year follow-up were 16.7 and 0, respectively (P<0.001). Observed medium-term morbidity included de novo urgency in four (5%), frequency in three (4%), and urge incontinence in one (1%). No patients reported graft erosion. The Uretex Urethral Support System is highly effective (both objectively and subjectively) for treatment of stress urinary incontinence and improves quality of life in women with minimal adverse sequelae.