The Effects of Vincristine on Milk Secretion and Milk Composition in the Goat

Abstract

SUMMARYThe effects of intramammary injection of vincristine on milk secretion were studied in goats. Vincristine inhibited milk secretion in a dose-dependent manner, with 1 mg decreasing milk yield to approximately 40% of previous yield. The inhibition was reversible with a full recovery of milk yield within a few days. During inhibition, there were significant changes in milk composition; Na concentration increased and K and lactose concentrations decreased, while Cl concentration was unaffected. Fat, protein, citrate and Ca concentrations all increased, particularly as milk yield was recovering. The concentrations in milk of the two lactose precursors, glucose and UDP-galactose, both increased. During inhibition and recovery, the secretion rates of three major components of milk, lactose, protein and fat, were affected to a different degree, with lactose secretion being inhibited to the greatest extent. The results are discussed in relation to the action of vincristine on milk secretion. It is proposed that vincristines actions include a specific inhibition of lactose synthesis.

Metabolites of Lactose Synthesis in Milk from Women During Established Lactation

“…In goats , there is a relationship between the concentrations of some of these and other metabolites in milk and their concentrations within the cell, and it has been proposed that the concentrations in milk reflect their Golgi vesicular and cytosolic concentrations (1). For example, the concentrations of these metabolites have been shown to vary in milk for goats during different stages of lactation and under different experimental conditions (2)(3)(4)(5)(6)(7). The changes in the concen-trations could be interpreted in terms of the metabolic changes that were occurring within the mamm ary gland at that time .…”