Sodium and potassium exchanges in adrenalectomized rats administered deoxycorticosterone chronically
Fifteen male adrenalectomized rats were divided into three equal groups and given powdered Purina diet and a choice between 0.30 M NaCl solution and distilled water. Body weight, intakes of food and fluids, urine output, and urine sodium and potassium concentrations were measured daily during a 7-day control period. At this time, two of the groups were administered 250 and 500 μg deoxycorticosterone acetate (DOCA) per kg body weight per day s.c. in oil. Controls received oil. The measurements listed above were taken for an additional 11 days of treatment. All groups ingested more NaCl solution than water during the control period. When DOCA was begun, both sodium output (meq/day) and intake (meq/day) were reduced proportionately and the linear relationship between them observed before treatment was maintained. Under these conditions adrenalectomized rats failed to escape from the sodium-retaining effects of DOCA. Furthermore, both the reduced output and intake of sodium remained for 10 days after drug administration ceased. Although administration of DOCA increased potassium excretion, food intake also increased such that the relationship between potassium intake and output observed before treatment was maintained. The urinary Na/K ratio was reduced significantly during drug treatment. The results suggest that mineralo-corticoid hormones are important in the control of both output and intake of sodium in the rat.