ISSN:
1432-1424
Keywords:
Active transport
;
oxidative metabolism
;
toad bladder
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Summary The use of an Ussing chamber with well-defined mixing characteristics coupled to a mass spectrometer permits the concurrent evaluation of transepithelial current and oxidative metabolism with improved temporal resolution. The time-course of the amiloride-sensitive currentI a and the rate of suprabasal CO2 productionJ CO2 sb were observed in 10 toad urinary bladders at short-circuit and after clamping ΔΨ at 100 mV, serosa positive. Following perturbation of ΔΨ (0→100mV),I a declined sharply within 1/2 min, remained near constant ∼15 min, and then increased slightly.J CO2 sb declined more gradually, remained near constant at ∼4–7 min, and then declined further. Detailed analysis revealed an early quasi-steady state with near constancy ofJ CO2 sb starting at 2.9±1.1 (sd) min and lasting 4.7 ±1.8 (sd) min, followed by relaxation to a later steady state at about 15 min. During the early quasi-steady state,I a was also nearly constant. Considering that in steady statesI a/F≃J Na a , the rate of transepithelial active Na transport, during the early quasi-steady state mean values ±se ofJ Na a ,J CO2 sb and (J Na a /J CO2 sb ) were, respectively, 29.9±1.7%, 59.4 ±3.2%, and 56.4±5.7% of values at short-circuit. Corresponding values during the late steady state were 41.4±6.0%, 38.2±6.1%, and 111.3±8.6%. Thus the flow ratioJ Na a /J CO2 sb was depressed significantly during the early quasi-steady state, but returned later to the original value. The results of measurements ofI a andJ CO2 sb in three hemibladders were qualitatively similar. In terms of a phenomenological “black-box” treatment the findings are consistent with earlier studies indicating incomplete coupling between transport and metabolism. Further studies will be required to clarify the molecular basis for these observations.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01870978
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