Renin-angiotensin-aldosterone system in rabbits with thoracic caval constriction
Lohmeier, T.E.; Davis, J.O.; Hanson, R.C.; Williams, G.M.
American Journal of Physiology 232(6): F559-F565
1977
ISSN/ISBN: 0002-9513 PMID: 879290 Document Number: 121348
The thoracic inferior vena cava was constricted sufficiently to produce salt and water retention and ascites in 37 New Zealand white rabbits. In a preliminary study, 9 animals retained Na and formed ascites, but after 8-24 days only 3 of the rabbits were still retaining Na (P < 0.01). At this time the rate of aldosterone secretion was elevated in these 3 animals only (P < 0.01) and plasma renin activity (PRA) was increased in only 1 of the 3 animals. In the definitive study, an acute experiment was performed after 72 h of caval constriction. At this time all the animals studied showed marked Na retention (0.6 meq/day on a Na intake of 8 meq/day) and ascites formation, and aldosterone secretion was elevated in 9 of 10 rabbits (from 3.3 to 21.9 ng/min, P < . 0.01). In only 4 of 22 animals PRA was elevated (from 9.8 to 18.5 ng angiotensin/ml, P < 0.025) and these rabbits had very high rates of aldosterone secretion (36 ng/min). The plasma K level was also elevated in association with a high rate of aldosterone secretion. A response in arterial pressure and aldosterone secretion to angiotensin II blockade was observed only in the rabbits with increased PRA. The increased aldosterone secretion was frequently mediated by an increase in PRA or hyperkalemia, or both. However, other factors such as a high plasma level of ACTH and increased adrenocortical K might have influenced aldosterone secretion.