Mechanism of Luteolysis and Vasoactive Agents in Cows

The corpus luteum (CL) forms after ovulation and plays an important role in the maintenance of pregnancy. Besides, it is a functional structure temporarily secreting progesterone and having endocrine activity. In cattle, the luteolysis generally occurs in two phases. These are classified as functional and structural luteolysis. Structural luteolysis is distinguished from the structural luteolysis with CL’s structural involution. During luteolysis, many vasoactive agents are stimulated such as nitric oxide, endothelin-I, angiotensin II, and oxytocin. In recent years, an increase has been found in the luteal blood flow at the beginning of the luteolysis, as determined by colour Doppler ultrasonography. The purpose of this review was to explain both various mechanisms about the vasoactive agents responsible in the luteolysis and their reciprocal interactions.