Because previous studies indicated that, in the rat collecting tubule, vasopressin (AVP)-sensitive adenylate cyclase (AC) is controlled by mineralocorticoids in the long term, the present study was designed to investigate whether such a control also exists in the short term. Therefore, we investigated the in vivo and in vitro effects of aldosterone on AC activity in cortical and outer medullary collecting tubules (CCD and OMCD, respectively) from adrenalectomized rats. Injection of aldosterone (10 micrograms/kg body wt) to adrenalectomized rats restored within 3 h AVP-sensitive AC activity in the CCD and OMCD up to the levels observed in the corresponding segments of adrenal intact rats. Similarly, incubating CCD or OMCD from adrenalectomized rats for 2.5 h in the presence of 10(-8) M aldosterone enhanced AVP-sensitive AC activity up to values similar to those found in normal rats. In vitro stimulation of AVP-sensitive AC activity was dose dependent with regard to aldosterone [apparent affinity constant (K0.5) approximately 10(-9) M], appeared after a 30-min lag period, and reached its maximum after 2-2.5 h. In addition, it was totally abolished by the antimineralocorticoid spironolactone, whereas the specific glucocorticoid antagonist RU 38486 had no effect. Finally, actinomycin D and cycloheximide totally abolished the in vitro action of aldosterone, demonstrating the involvement of protein synthesis in that process.
In Vitro Effects of Yessotoxin on a Primary Culture of Rat Cardiomyocytes
