Hormonal control of sodium content in human milk.

The possible role of prolactin (PRL) and aldosterone (Aldo) in regulation of Na content of human milk was investigated. Simultaneous determinations of Na and K in milk, PRL and Aldo in maternal plasma and milk were performed on postpartum days 2, 4 and 6, in samples from 15 mothers giving birth at term and from 8 mothers giving preterm birth. Na concentration and Na/K ratio in milk, Aldo concentration in milk and maternal plasma decreased significantly with advancing lactation.

Activity of the renin-angiotensin-aldosterone system in full-term newborn infants during the first week of life.

A study was performed in 7 healthy full-term newborn infants with mean birth weight of 3130 g (range, 2650-2850 g) and a mean gestational age of 38.8 weeks (range, 37-41 weeks) to investigate the postnatal changes of plasma renin activity (PRA), plasma aldosterone concentration (PA) and urinary aldosterone excretion (UAE) in relation to electrolyte balance. PRA, PA and UAE fell significantly from their initially high values of 28.