Endocrine Abstracts

It has previously been shown that protein restriction during pregnancy impairs the physiological adaption to pregnancy by reducing plasma volume expansion. This may mediate the effects of maternal diet on placental and fetal development. This study investigated the mechanisms by which maternal diet interacts with plasma volume expansion.

Female Wistar rats were mated and fed a control (18%, n=32) or low protein (9%, n=32) diet during pregnancy. On days 5, 10, 15 or 20 (n=8 per group per age) of gestation, plasma volume was determined by i.v. infusion of Evans blue dye under terminal anaesthesia. Creatinine clearance was estimated as a measure of glomerular filtration rate. Expression of regulatory components of renal fluid homeostasis were assessed by RT-PCR and Western blot, normalised to β-actin and tubulin respectively.

Plasma volume was significantly altered by gestational age (P<0.05), increasing over time. Although there appeared to be a delay in volume expansion in low protein animals, there was no statistically significant interaction of gestational age with diet. There was a significant interaction between gestational age and diet in their effects on aquaporin 2 protein expression (P<0.05). Expression was reduced to 28% of that observed at oestrous by day 5 of gestation in low protein animals. In contrast, this reduction was not observed in control animals until day 10. The expression of aquaporin 3 and the type 1a angiotensin receptor were not affected by gestational age or diet.

In conclusion, the level of protein restriction used in this study was not sufficient to impact upon plasma volume expansion to the extent observed in previous studies. However, effects were observed on creatinine clearance and aquaporin 2 expression, which plays a key role in fluid homeostasis. Future studies will examine further aspects of maternal adaptation to pregnancy in response to a range of dietary interventions.