Date of Award


Document Type


Degree Name

Master of Science




Prolactin (PRL) acts directly on milk secretory cell nuclei to stimulate lactation in rats. In the cow, PRL has been detected in Golgi apparatus, endoplasmic reticulum, and secretory vesicle subcellular fractions of mammary gland , but not nuclear fractions. However, growth hormone {GH) is the galactopoeitic hormone in cows, not PRL. The possibility of GH acting directly on the cow milk secretory cells, and PRL acting on their nuclei was investigated using an immunocytochemical method. PRL and GH were detected in endoplasmic reticular and Golgi apparatus regions of the milk secretory cells, as well as, on nuclear and fat globule membranes . PRL and GH were both detected in the alveolar milk. Therefore, it appears that GH and PRL act directly on the milk secretory cells of the cow.