Prehypertensive Dahl S rats show no rise in glomerular filtration rate after an amino acid infusion.

: When one administers a protein or amino acid load, both GFR and renal blood flow increase about 40% in normal humans as well as in dogs and rats. The protein load causes vasodilation in both the afferent and the efferent arterioles. In these prehypertensive Dahl S rats, it is likely that there is already some vasodilation of the afferent and efferent arterioles and possibly some mesangial relaxation, in order to bring the GFR to normal levels in the face of some intrinsic abnormality in glomerular filtration. Since these arterioles are already dilated, there can be little further dilation in response to the amino acid load and hence no further increase in GFR. It is possible that this limited capacity for further vasodilation could serve as a predictor of future hypertension.