John D. Imig
In the current set of experiments it is very difficult to separate the actions of chronic angiotensin II infusion from the elevation in mean arterial pressure. Previous studies have demonstrated that in normotensive animals the afferent arteriolar response to increases in renal perfusion pressure is not significantly altered by the presence of angiotensin II. Interestingly, the tubuloglomerular feedback response, which influences primarily the distal portion of the afferent arteriole, is enhanced during acute elevations of circulating angiotensin II levels.
Additionally, we have done a more thorough evaluation of the afferent arteriolar response to increases in perfusion pressure during various time points in the development of angiotensin II-induced hypertension. We have observed an impairment of the afferent arteriolar autoregulatory response after one week of angiotensin II infusion which starts to improve at 10 days and is similar to normotensive animals by two weeks (Abstract, J Am Soc Nephrol 9:308A, 1998). This would suggest that the renal microvasculature is adapting to the elevated blood pressure and/or angiotensin II levels to properly control renal blood flow and glomerular filtration.
John D. Imig