Age-related changes in angiotensin II-stimulated proximal tubule fluid reabsorption in the spontaneously hypertensive rat.
The development of hypertension in the spontaneously hypertensive rat (SHR) up to 8 weeks of age involves sodium retention with reduced fractional sodium excretion. Since angiotensin II (Ang II) directly stimulates proximal tubular sodium transport, we investigated age-related changes in proximal reabsorption (Jv), using shrinking split-drop micropuncture before and after enalaprilat in SHR at 5, 7 and 12 weeks of age and in age-matched Wistar-Kyoto rats (WKY). Control values for Jv were higher in the SHR than in WKY at 5 weeks, but lower at 7 and 12 weeks, consistent with an early phase of sodium retention. Enalaprilat reduced mean Jv by approximately 15% in all WKY groups, indicating the extent of Ang II-stimulated transport. In the SHR there was an age-dependent reduction in the effect of enalaprilat on Jv, and by 12 weeks no Ang II stimulation could be detected. Age-related changes in proximal tubular reabsorption could contribute to sodium retention in the young SHR and may reflect a more general pattern of inherited transport defects.
Thomas
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D
Department of Physiology, University of Melbourne, Parkville, Victoria, Australia.
Harris
P J
PJ
Morgan
T O
TO
D000375:Aging; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004656:Enalapril / Q000031:analogs & derivatives / Q000494:pharmacology; D015773:Enalaprilat; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D051381:Rats; D011918:Rats, Inbred SHR / Q000502:physiology*; D011919:Rats, Inbred Strains / Q000502:physiology*; D014882:Water-Electrolyte Balance / Q000187:drug effects
D000804:Angiotensin II; D004656:Enalapril; D015773:Enalaprilat