Although it is known that estrogen reduces renal Na excretion, the precise mechanism has not been determined. A recent study has demonstrated that 3H metolazone-binding in the rat kidney is reduced by ovariectomy (OVX), which suggests that sex hormones may affect either the density or binding capacity of the TSC. Therefore, we employed immunogold cytochemistry to determine the effect of OVX and estrogen replacement on the ultrastructural localization of the TSC in rat kidney. OVX Sprague-Dawley rats were fed standard rat chow ad lib for 9 wks before their kidneys were perfused in vivo with glutaraldehyde and processed in Lowicryl K4M. Transmission electron microscopy (TEM) revealed a reduction in apical plasma membrane microprojections in the DCT of OVX rats. Immunogold localization using a polyclonal antibody against a 110 aa N' terminal fragment of rat TSC (Plotkin, et al, JASN 6:1995, abstr., in press) demonstrated intense label for TSC in the apical plasma membrane of the DCT in intact female rats (CON,n=6). In OVX rats (n=6), label for TSC was present in the apical plasma membrane of the DCT, but label intensity was markedly reduced. Urinary Na excretion rates (UNaV) 8 wks post-OVX were CON 136.4±33.0 vs OVX 164.3±68.9 μEq/24h/100g BW, p = NS. Similar ultrastructural findings were observed in pair-fed CON (n=3) and OVX (n=3) rats 9 wks post-OVX. UNaV were CON (n=8) 171.91±71.6 vs OVX (n=9) 207.9±76.0 μEq/24h/100g BW, p=NS. Additional OVX rats (n=6) received 10μg/kg BW 17β-estradiol in corn oil SC 4 X/wk for 9 wks and the kidneys were processed for TEM. In these, DCT apical microprojections and gold label for TSC were not different from CON and UNaV was 190.6±58.8 μEq/24h/100g BW. These data demonstrate that in ovariectomized rats 1) the amount of apical plasma membrane and immunogold label for TSC in the DCT is decreased and 2) estrogen replacement restores the DCT apical plasma membrane and TSC label to normal. We conclude that estrogen enhances the density of TSC in the DCT and thus may alter renal sodium transport and consequently calcium transport by this mechanism.
|Original language||English (US)|
|Journal||Journal of Investigative Medicine|
|State||Published - Jan 1 1996|
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)