Soidum requirement of the rat during pregnancy

The sodium requirement for the pregnant rat was established on the basis of a series of studies in which the following parameters were investigated on varying levels of soidum intake: sodium retention, plasma and tissue sodium concentrations, hematocrit, juxtaglomerular index (JGI), zona glomerulosa (ZG) width, ultrastructure of the ZG cell, and aldosterone-producing capacity of the ZG cell. The recommended level of 26 mEq sodium/100 g diet was identified as the level of intake that permitted the pregnant rat to achieve the homeostatic adjustment to sodium need with as little apparent stress on the JGI and ZG as in nonpregnant rats; as a criterion, we used thepoint in the continuum of physiological adjustment where the first recognizable changes in cellular morphology could be identified. These data, along with addtional data on blood pressure and renal medullary lipid concentration, indicate that during pregnancy a chronology of events occurs which suggests a working model for the maintenance of sodium homeostasis and blood pressure regulation.