SHORT-TERM EFFECT OF ALDOSTERONE ON VASOPRESSIN-SENSITIVE ADENYLATE-CYCLASE IN RAT COLLECTING TUBULE

Because previous studies indicated that, in the rat collecting tubule, vasopressin (AVP)-sensitive adenylate cyclase (AC) is controlled by m ineralocorticoids in the long term, the present study was designed to investigate whether such a control also exists in the short term. Ther efore, we investigated the in vivo and in vitro effects of aldosterone on AC activity in cortical and outer medullary collecting tubules (CC D and OMCD, respectively) from adrenalectomized rats. Injection of ald osterone (10 mug/kg body wt) to adrenalectomized rats restored within 3 h AVP-sensitive AC activity in the CCD and OMCD up to the levels obs erved in the corresponding segments of adrenal intact rats. Similarly, incubating CCD or OMCD from adrenalectomized rats for 2.5 h in the pr esence of 10(-8) M aldosterone enhanced AVP-sensitive AC activity up t o values similar to those found in normal rats. In vitro stimulation o f AVP-sensitive AC activity was dose dependent with regard to aldoster one [apparent affinity constant (K0.5) almost-equal-to 10(-9) M], appe ared after a 30-min lag period, and reached its maximum after 2-2.5 h. In addition, it was totally abolished by the antiminer-alocorticoid s pironolactone, whereas the specific glucocorticoid antagonist RU 38486 had no effect. Finally, actinomycin D and cycloheximide totally aboli shed the in vitro action of aldosterone, demonstrating the involvement of protein synthesis in that process.