AJP - Renal Physiology, Vol 243, Issue 1 74-F80, Copyright © 1982 by American Physiological Society

ARTICLES

Bicarbonate reabsorption in the papillary collecting duct: effect of acetazolamide

R. M. Richardson and R. T. Kunau Jr

The present study was designed to characterize bicarbonate (total CO2) reabsorption in the papillary collecting duct of the kidney of the Munich-Wistar rat when total CO2 delivery to this segment was increased by the systemic infusion of a bicarbonate-rich solution. Additional studies examined the effect of the systemic administration of acetazolamide, a carbonic anhydrase inhibitor, on total CO2 reabsorption. Employing free-flow micropuncture techniques, tubular fluid samples were obtained from the base and tip of the exposed papilla and subsequently analyzed for total CO2 and inulin. Total CO2 reabsorption increased in a linear fashion, approximating 34% of that delivered to the base, as total CO2 delivery increased from 3 to 20% of the filtered load. When examined at comparable absolute rates of total CO2 delivery (mumol/min) to the papillary collecting duct, acetazolamide administration resulted in marked inhibition of total CO2 reabsorption. The results of these studies suggest that the papillary collecting duct of the rat kidney possesses a significant capacity for reabsorption of total CO2 and that this reabsorption is diminished by the administration of acetazolamide.

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