Gluco- and mineralocorticoids control adenylate cyclase in specific nephron segments

Adrenal insufficiency is associated with an impairment of kidney diluting and concentrating ability, defects that may result from alterations of vasopressin-induced adenosine 3',5'-cyclic monophosphate (cAMP) production. The purpose of this study were 1) to localize the sites of decreased vasopressin-stimulated adenylate cyclase (AC) activity along the nephron of adrenalectomized rats; 2) to determine whether the response of AC to other hormones is altered by adrenalectomy; 3) to evaluate whether changes in AC are due to the deficiency in mineralocorticoids and/or glucocorticoids; and 4) to characterize the mechanism of action of corticosteroids on the AC system. Results indicate that adrenalectomy reduced AC stimulation by vasopressin, glucagon, and calcitonin in the thick ascending limb, whereas only the response to vasopressin decreased in the collecting tubule. Glucocorticoid administration curtailed adrenalectomy-induced alterations of AC in the thick ascending limb, whereas that in the collecting tubule was prevented by mineralocorticoids. Adrenalectomy did not alter forskolin-stimulated AC, whereas it decreased responses to aluminum fluoride and cholera toxin. Finally, alterations of fluoride- and cholera toxin-stimulated AC were prevented by glucocorticoid and mineralocorticoid repletion in the thick ascending limb and collecting tubule, respectively.