Water and sodium intake induced by water deprivation in high fat diet ovariectomized rats with 17-beta-estradiol replacement

Water deprivation (WD) is a common situation in nature and induces water and sodium intake. In ovariectomized female rats, the replacement with 17β-estradiol (E2) reduces the water and sodium intake induced by WD. Experimentally, obesity reduces daily water intake and WD-induced water intake in male rats. Since the increased rates of obesity in females after menopause, we aimed to verify the WD-induced water and 0.3 M NaCl intake in standard diet (SD, 11% calories from fat) and HFD (45% calories from fat) female OVX rats with or without E2 replacement. Female Holtzman rats (260 –300g) at week 0 underwent OVX and part of the SD and HFD fed rats received in the 4th week a mini-pump with E2 (10μg/day/rat) for the next 4 weeks, resulting in 4 groups: SD-OVX (n=12), SD-OVX+E2 (n=8), HFD-OVX (n=13), HFD-OVX+E2 (n=8). We used WD-partial rehydration protocol to induce thirst and sodium appetite. Briefly, rats were maintained during 24 h with access to only food pellets. After this, WD rats were allowed to drink only water for 2 h until satiety and then animals had access to a 0.3 M NaCl for a salt appetite test (2 h). The fluid intake is expressed in ml/100 g of body weight. At the 6th week after OVX and diet (HFD or SD), daily water intake was reduced in HFD-OVX compared to week 0 (5.7 ± 0.5 vs. week 0: 8.9 ± 0.5 ml/24 h, p < 0.05) returning to baseline levels after E2 administration (7.9 ± 0.9 ml/24 h). Conversely, 0.3 M NaCl intake was increased in HFD-OVX rats (4.5 ± 1.1 vs. week 0: 1.4 ± 0.4 ml/24 h, p, 0.05) and reduced after E2 replacement. Daily water and sodim intake were greater in HFD-OVX than SD-OVX rats before E2 replacement. After WD, HFD-OVX rats ingested less water than SD-OVX rats (3.1 ± 0.2 vs. SD-OVX: 4.1 ± 0.3 ml/2 h; p < 0.05) and E2 did not significant change this response in SD or HFD OVX rats. There was no significant change in 0.3 M NaCl intake induce by WD between SD-OVX and HFD-OVX rats (SD-OVX: 2.0 ± 0.2 and HFD-OVX: 1.4 ± 0.2 ml/2h; p = 0.08). However, the sodium intake induce by WD in SD-OVX rats was reduced by E2 (1.2 ± 0.2 vs. SD-OVX; p < 0.05) and a natriorexigenic response was observed in HFD-OVX+E2 rats (2.1 ± 0.2 vs. HFD-OVX; p < 0.05). The increase in visceral adipose tissues in HFD-OVX was reversed in HFD-OVX-E2 group and uterus weight was greater in OVX SD and HFD groups after E2 treatment. These results demonstrated that obesity induces a decrease in daily water and increase in daily sodium intake in OVX rats. E2 treatment can restore these effects. In additon, HFD-OVX rats drank less water induce by WD, which was restored by E2 treatment. Finally, in HFD fed female OVX rats, E2 have an excitatory effect on WD-induced sodium intake, as oppose to the well known anti-dipsogenic effect of E2 in SD-OVX rats under WD. Support: CAPES, FAPESP, CNPq. Nothing to disclose This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.