AJP - Heart and Circulatory Physiology, Vol 249, Issue 2 415-H420, Copyright © 1985 by American Physiological Society
Fluid volumes and hemodynamics in hypertension produced by chemical renal medullectomy
D. Taverner, R. F. Bing, J. D. Swales and H. Thurston
We have investigated the mechanisms by which chemical renal medullectomy
with 2-bromoethylamine hydrobromide (200 mg/kg body wt) produces
hypertension in rats. Groups of chemically medullectomized rats were
compared with normal rats and rats that had been partially nephrectomized
to produce an equivalent fall in glomerular filtration rate. Mean arterial
pressure was elevated in the medullectomized (142 +/- 6 mmHg) compared with
normal rats (124 +/- 3). In the medullectomized animals this was associated
with significant tachycardia (483 +/- 15 vs. 450 +/- 6 beats/min) and an
increase in cardiac output (61.1 +/- 5.0 vs. 49.9 +/- 2.2 ml X min-1 X 100
g body wt-1). Plasma volume was significantly reduced in medullectomized
rats (2.16 +/- 0.15 vs 3.29 +/- 0.20 ml/100 g body wt), whereas
exchangeable sodium was unchanged (39.9 +/- 0.5 vs. 39.7 +/- 0.5 meq/kg
body wt). By contrast, both plasma volume and exchangeable sodium were
increased in partially nephrectomized rats. These results are consistent
with the hypothesis that chemical medullectomy produces hypertension by
increased selective sympathetic efferent activity, raising cardiac output
and postcapillary venular resistance. This may be the consequence of
reducing the secretion of a renomedullary humoral substance that normally
inhibits such activity.
