Equine luteinizing hormone possesses follicle-stimulating hormone activity in hypophysectomized female rats.

The research article investigates the potential of equine luteinizing hormone (eLH) to stimulate follicular growth and development in rats without a pituitary gland, demonstrating that eLH possesses follicle-stimulating hormone-like activity, though less potent than equine chorionic gonadotropin.

Overview of the Research

• The research explored the functionality of equine luteinizing hormone (eLH)—a hormone found in horses—in promoting growth and maturation of follicles in hypophysectomized rats. Hypophysectomy is a process where the pituitary gland of the rats is removed, thus they are unable to produce certain hormones naturally.
• The focus of the research was to illustrate that eLH has intrinsic follicle-stimulating hormone (FSH) activity. FSH is vital for the growth of ovarian follicles, which are small sacs in the ovaries that contain the immature eggs.

Method and Findings

• A single injection of eLH led to the development of a significant number of antral and preovulatory follicles, increased the levels of estrogen in the serum, and ushered an increase in uterine weight.
• Furthermore, eLH significantly enhanced the integration of [3H]thymidine into ovarian DNA, which indicates the replication of ovarian cells. This amplified integration, exhibited by eLH, is an attribute associated with hormones having follicle-stimulating hormone activity.
• To ensure the observed FSH activity was solely attributable to eLH, it was treated with an FSH antibody immunoaffinity column to remove any potential contamination. The hormone retained its characteristics, suggesting the FSH-like activity is essential to eLH.
• In addition, eLH was found to induce LH receptors in granulosa cells, which assist the follicle growth in the ovaries of the hypophysectomized rats. This induction capability is also particular to FSH-like hormones.

Concluding Observations

• Though eLH displayed FSH-like activity in hypophysectomized rats, it was found to be less active than equine chorionic gonadotropin, a potent hormone vital for ovarian follicle stimulation in mammals.
• The doses required and the extent of the response observed led to this conclusion, offering new insights into the role of equine luteinizing hormone and its potential applications in fertility treatment scenarios.