Lactation: some cardiovascular and metabolic consequences, and the mechanisms of lactose and ion secretion into milk.

Lactation causes increases in mammary blood flow, gastrointestinal blood flow and cardiac output in the rat, and the suckling-induced release of lactogenic anterior pituitary hormones probably causes these changes, directly or indirectly. Metabolic requirements of lactation in women are similar to those in other animals not artificially selected for a high milk yield but the physiological control of the relationship between milk secretion and nutrient availability is not well understood. The unusual composition of the aqueous phase of human milk (rich in lactose but poor in sodium and potassium ions) can be explained by the same basic mechanisms for secretion of lactose and ions as operate in other animals but with quantitative differences.