Influence of the renal medulla and early treatment with enalapril upon the development of hypertension in young spontaneously hypertensive rats.
OBJECTIVE
To investigate the role of the renal medulla in early hypertension in spontaneously hypertensive rats (SHR), and to explore whether the attenuated increase of pressure induced by enalapril treatment is affected by chemical medullectomy.


METHODS
Forty-four male SHR were studied from 5 to 18 weeks of age: 22 remained intact; 22 were medullectomized at 5.5 weeks of age with 2-bromoethylamine hydrobromide; 11 of each of these two groups were treated with enalapril from 6 to 12 weeks of age. Blood pressure, heart rate and body weight were recorded intermittently, and at 18 weeks renal function was also analysed.


RESULTS
The results indicate a protective effect of the renal medulla against severe pressure rises in SHR, although even when enalapril also lowered blood pressure in medullectomized SHR, persistent improvements of glomerular filtration rate and renal flow conductance occurred only in intact SHR. Furthermore, after enalapril treatment ended blood pressure rose to higher levels in medullectomized SHR, despite greater sodium-water losses.


CONCLUSIONS
The renal medulla seems to exert a protective role both during and after enalapril treatment.
Bergström
G
G
Department of Physiology, University of Gothenburg, Sweden.
Bohman
S O
SO
Folkow
B
B
Göthberg
G
G
Rudenstam
J
J
Karlström
G
G
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D004656:Enalapril / Q000494:pharmacology*; D005021:Ethylamines; D005919:Glomerular Filtration Rate / Q000187:drug effects; D006321:Heart / Q000033:anatomy & histology / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000209:etiology*; D007668:Kidney / Q000187:drug effects*; D007679:Kidney Medulla / Q000473:pathology / Q000503:physiopathology*; D008297:Male; D009336:Necrosis / Q000139:chemically induced; D009929:Organ Size / Q000187:drug effects; D051381:Rats; D011918:Rats, Inbred SHR; D012079:Renal Circulation / Q000187:drug effects
D005021:Ethylamines; C004504:2-bromoethylamine; D004656:Enalapril