Age-related changes in Na+ excretion in saline-loaded spontaneously hypertensive rats
Mullins, M.M.; Banks, R.O.
American Journal of Physiology 231(5 Pt. 1): 1364-1370
1976
ISSN/ISBN: 0002-9513 PMID: 998778 Document Number: 96544
Female spontaneously hypertensive rats (SHR) from 2 colonies were studied as to their ability to excrete an isotonic saline load equivalent to 4.5% of bodyweight. They were 6 to 7, 12 to 13, and 16 to 17 weeks old. Female Wistar (W) and Wistar-Kyoto (WKY) rats of the same ages were controls. At 6 weeks old, the fraction of administered Na+ load excreted by either SHR colony in 60 min was less than in the W rats but not significantly different from that in the WKY rats. At 12 weeks all rats excreted similar fractions of the Na+ load in 60 min. At 16 weeks one SHR colony excreted more Na in 60 min than the other rats. Glomerular filtration rate during control periods was positively related with age in one SHR colony; no age-related change was found in glomerular function in the other groups. The results suggest tht WKY rats are more appropriate than W rats as controls for renal function in the SHR. They also show that the ability of SHR to excrete a Na load is equal to or greater than that of normal WKY controls and that with regard to renal function the SHR is not a homogeneous strain.