Effect of Cholera Toxin on Renal Tubular Reabsorption of Glucose and Bicarbonate 1

Summary

Cholera toxin (CT) reduces tubular reabsorption of Na, Cl, Ca, Mg and P most probably through stimulation of a renal adenylate cyclase-cyclic AMP system, and it is possible that an increased production of nephrogenous cyclic AMP during extracellular fluid volume expansion may be partly responsible for the observed natriuresis. In order to further evaluate the role of renal cyclic AMP in renal tubular transport, we studied the effect of CT on glucose (TRG) and bicarbonate reabsorption (TRHCO₃).

During the period of maximal effect of CT on tubular transport (100-140 min of CT infusion into one renal artery) both the TRG and TRHCO₃ were lower in the infused kidney than in the contralateral noninfused kidney; TRG as mg per 100 ml GFR was 254 ± 32.7 vs 363 ± 43.5 (P < .01), and TRHCO₃ as mEq per 100 ml GFR was 2.09 ± 0.06 vs 2.53 ± 0.06 (P < .01). The data indicate that CT suppresses glucose and bicarbonate reabsorption together with that of sodium and as such assign to role for renal cyclic AMP in the regulation of the tubular transport of these substances.

The authors wish to thank Mr. Barry Gammel and Mrs. Verginia Barbarian for their technical assistance, and Ms. Melinda Ayers, Ms. Jamie Jimenez, Ms. Alice Moomjean and Ms. Alberta Ward for their secretarial assistance.