Role of Milk Secretion in Transport of Prolactin from Blood into Milk

Summary

In a first experiment prolactin was shown to be uniformly distributed in the milk of dairy cows. Accumulation of prolactin in milk increased with milking interval although milk prolactin content was proportionally greater after 2 h than accumulation of milk.

Concentration of milk prolactin and total transfer of prolactin into milk was greater in mammary glands of cows milked just prior to initiation of intravenous infusion of exogenous prolactin.

Similarly, inhibition of milk secretion as induced by intramammary infusion of colchicine, markedly reduced milk prolactin concentration and total transfer of prolactin into milk 5h following start of intravenous infusion of exogenous prolactin.

Data indicate that transfer of prolactin from blood into milk during established lactation occurs primarily in conjunction with milk secretion.

Key-Words

Prolactin - Hormones in Milk - Milk Secretion - Mammary Gland - Milk Secretion - Udder