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(Hypertension. 2000;35:875.)
© 2000 American Heart Association, Inc.

Scientific Contributions

Role of Citrate Synthase in Aldosterone-Mediated Sodium Reabsorption

Presented in part at the annual meeting of the Council for High Blood Pressure Research of the American Heart Association, Philadelphia, Pa, September 1998, and published in abstract form.

Michael E. Ullian; Christopher J. Robinson; Claudia T. B. Evans; Joel Z. Melnick; Wayne R. Fitzgibbon

From the Medical University of South Carolina (M.E.U., C.J.R., W.R.F.), Charleston, SC; University of Texas Southwestern Medical School (C.T.B.E.), Dallas, Tex; and Northwestern University School of Medicine (J.Z.M.), Chicago, Ill.

Correspondence to Dr Michael E. Ullian, Medical University of South Carolina, Division of Nephrology, Department of Medicine, Clinical Sciences Building 829, 171 Ashley Ave, Charleston, SC 29425. E-mail ullianme{at}musc.edu

Abstract—Aldosterone and other mineralocorticoids increase citrate synthase activity in the kidney and enhance renal sodium reabsorption, but it is unclear whether the increased citrate synthase activity is involved in renal sodium transport. We used the Wistar-Furth rat, an inbred strain found to be deficient in renal citrate synthase activity, as an experimental model to investigate this issue. We confirmed that renal citrate synthase activity from adrenalectomized Wistar-Furth rats was decreased compared with that from control Wistar rats (by 28%). Similarly, urinary citrate excretion was 23% lower in Wistar-Furth rats. Subnormal citrate formation in Wistar-Furth rats could not be accounted for by differences in systemic pH or circulating potassium levels. Because renal citrate synthase activity was reduced in Wistar-Furth rats, we hypothesized that renal sodium excretory responses to mineralocorticoids would be reduced as well. Four-hour sodium excretion after intraperitoneal injection of 5 µg of aldosterone was reduced by 56% in adrenalectomized Wistar rats and by 52% in adrenalectomized Wistar-Furth rats (both P<0.01 compared with vehicle injection). Similarly, the pattern of urinary sodium excretion in response to subcutaneous injections of deoxycorticosterone acetate over a 2-week period was similar in adrenalectomized Wistar and Wistar-Furth rats. In summary, acute and chronic antinatriuretic responses to mineralocorticoids are maintained in Wistar-Furth rats at the level of Wistar rats, despite the marked reduction in citrate synthase activity. These findings are not consistent with an important role for citrate synthase activity in mineralocorticoid-mediated renal sodium transport.

Key Words: rats, Wistar-Furth • rats, Wistar • aldosterone • mineralocorticoids • sodium • deoxycorticosterone acetate