Carbenoxolone does not cause a syndrome of mineralocorticoid excess in sheep

Abstract

These studies investigated whether treatment with carbenoxolone (CBX), an inhibitor of 11β-hydroxysteroid dehydrogenase (11β-HSD), resulted in an enhanced mineralocorticoid response to endogenous or infused cortisol. In conscious sodium replete sheep with a parotid fistula, infusion of CBX (40 mg/h for 10 days) did not increase mean arterial pressure, or change sodium and potassium status or plasma renin concentration, but significantly increased the half-life of 1, 2[ 3H] cortisol from 18.6 ± 4.0 to 38.8 ± 3.9 min ( p < 0.05) and reduced the blood clearance rate of cortisol (BCR) from 31 ± 3 to 15 ± 4 L/h ( p < 0.01). The reduction in cortisol BCR was associated with reduction in cortisol secretion rate from 433 ± 116 to 181 ± 79 nmol/h ( p < 0.01). Cortisol (8 mg/h) for 5 days increased mean arterial pressure (from 83 ± 2 to 101 ± 5 mmHg, p < 0.001) and caused natriuresis, hypokalaemia and hyperglycaemia. These responses were unaltered when cortisol was infused from the fifth to the tenth day of CBX infusion. These findings suggest that in sheep, carbenoxolone is either a less potent inhibitor of 11β-HSD2 than in other species or 11β-HSD2 may not be the only mechanism, which determines the specificity of the MR.