ROLE OF UTERINE FACTORS IN THE DEVELOPMENT OF HYPERTENSION IN SHR

1. To examine whether the uterine environment plays a role in the deve lopment of hypertension in the spontaneously hypertensive rats (SHR), we have compared fetal weight, placental weight, and amniotic fluid co mposition of SHR and Wistar-Kyoto (WKY) rats after 20 days of gestatio n. 2. Pregnant SHR and WKY were anaesthetized at 20 days of gestation and the uterus and embryonic sacs removed. Fetal and placental weights were recorded and amniotic fluid collected for measurement of volume, osmolality and electrolyte composition. 3. No significant difference was found in litter size and placental weight between SHR and WKY. Tot al embryonic sac weight and fetal weight of SHR were significantly low er than WKY. Amniotic fluid volume, sodium concentration and osmolalit y of SHR were significantly higher than WKY, while amniotic fluid pota ssium concentration of SHR was significantly lower than WKY. 4. Thus, the SHR foetus was significantly underweight compared to the WKY and w as bathed in amniotic fluid with a significantly higher osmolality and sodium concentration. As the mature foetus is known to drink amniotic fluid, it is hypothesized that the elevated Na/K ratio in SHR amnioti c fluid may instigate or accelerate the hypertensive process.