Effect of Various Hormones on the Milk Ejection Response of Tissue isolated from the Rat Mammary Gland

Abstract

A SENSITIVE in vitro bioassay for oxytocin has been developed which makes use of the milk-ejection response of tissue from the mammary gland of lactating rats¹. The object of the present experiments was to determine the specificity of this assay. The specificity of the response of mammary gland tissue to oxytocin, in vitro, has been a matter of controversy ever since Mendez-Bauer et al.² used the response of this tissue as a quantitative assay for oxytocin. These workers reported that the contractions of rabbit mammary strips were highly specific for oxytocin. Subsequently other investigators found that mammary strips from lactating rats contracted in response to a variety of substances, for example, arginine–vasopressin^3,4, acetylcholine, epinephrine, norepinephrine, histamine and 5-hydroxytryptamine⁴. Mammary strips from lactating rabbits contracted when exposed to arginine–vasopressin and to acetylcholine⁵.