Hormonal Changes ·during Formation and Involution of Corpus Luteum in Rabbits

Labib F., E. A. El Azab, F. A. Soliman: Hormonal Changes During Formation and Involution of Corpus Luteum in Rabbits. Acta vet. Brno, 47, 1978: 23-31. A study was made on 30 female Boscat rabbits to reveal the hormonal changes, namely, TSH, FSH, LH and L TH during the formation, maintenance and involution of the corpora lutea. Induction of ovulation was done by using gonadotrophic hormones (PMS and HCG). After HCG injection the animals were devided into 3 groups of 10 animals each. They were slaughtered after 3, 7 and 15 days from HCG injection. The results observed from this experiment are as follows: 3-day old corpus luteum The rate of synthesis and release of TSH and state of thyroid were considered in a stabilized, balanced euthyroid status. There was increased concentration of FSH in the pituitaries with a relatively low level in the blood. This indicates the inhibition of release of FSH at this stage of development of corpora lutea. The level of L TH in the pituitary was of an average value and low in the serum. 7-days old corpus luteum The TSH content of the pituitaries was the lowest (decreased synthesis) with a mild change in its level in the blood (non-significant). The thyroids were relatively less active than in the previous group. The FSH content of the pituitaries and blood were significantly decreased (decreased synthesis and release of FSH). The LH content of the pituitaries was increased and the level in the blood was decreased (decreased release of LH). The L TH content of the pituitaries was relatively low, while that of the blood was maximal, indicating increased release of L TH. IS-day old corpus luteum The TSH content of the pituitaries and blood were highest indicating increased synthesis and release of this hormone. The thyroid gland showed maximum activity as compared to the previous groups. The FSH content of the pituitaries was relatively low while it reached its maximum in the serum (increased rate of release of FSH). The level of LH in the pituitaries was low and that of the blood was the least. The L TH content of the pituitaries was at its maximum and it was the lowest in the blood (increased synthesis of L TH but blocked release into the blood). The results are discussed in the text. LTH, TSH, LH, FSH, pituitary, blood serum. The features of growth and maintenance of the corpus luteum, and its subsequent involution are active processes of extreme importance in regulating reproductive performance of mammals. This includes regulation of the estrous cycle, pregnancy, parturition and milk production. Any disturbance of such processes of the corpus luteum will lead to reproductive disturbances in the farm animals.