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Cellular and Molecular Regulation of Luteal Formation, Function, and Regression: An Introduction

^a Division of Animal and Veterinary Sciences, West Virgina University, Morgantown, West Virginia 26506-6108

The corpus luteum (CL) plays a major role in the regulation of the estrous or menstrual cycle and is also essential to at least the initiation of pregnancy in mammals. I was introduced to the CL in Harold Kidder's class in Reproductive Physiology at West Virginia University in 1958. As a graduate student at Wisconsin, Kidder had been the first to show that the CL of the sow was maintained beyond its normal life span by an injection of estrogen on Day 11 after estrus [1]. In the fall of 1960, L.E. Casida asked me, a student at Wisconsin at that time, to begin studies of factors affecting the life span of the CL in the ewe. These studies were based on work by Zavadovski et al. [2] and Casida et al. [3] on the effect of induced CL on the length of the estrous cycle; the finding by Jim Wiltbank that hysterectomy prolonged luteal function in ewes and cows [4]; and the intriguing reports from Andy Nalbandov's laboratory that beads placed into the uterine lumen could either shorten or lengthen luteal life span in the ewe [5, 6]. During the 1960s and the 1970s, the various luteotropic and luteolytic factors that alter the life span and function of this unique endocrine gland were elucidated.

My fascination with the CL became admiration of its secretory powers as a result of two observations. First, Stormshak et al. [7] showed that the amount of progesterone contained in the CL of the ewe was secreted from the gland every 4 min. Second, Tanabe [8] demonstrated how much progesterone was required to replace the CL to maintain pregnancy at different stages of gestation in the cow. More recent studies have begun to unravel the complexity of regulation of luteal formation, function, and regression using the tools of molecular biology.

Because of my long-standing interests in the CL, I agreed to organize a minisymposium addressing the molecular biology of the corpus luteum for the 1999 annual meeting of SSR. It was decided to consider the formation, function, and regression of the CL in the three talks. Presenters of two of these talks prepared minireviews, which have been reviewed and accepted for publication in Biology of Reproduction. After consultation with Editor Mahesh, we decided to place a previously reviewed and accepted paper from my laboratory in sequence with these papers by Bruce Murphy and Fred Stormshak et al. This paper discusses some of the basis for our more recent understanding of luteal regression in ruminants. It is our hope that these three papers provide a provocative unit on current research in the molecular biology of the corpus luteum and that they will stimulate new ideas by others, as the minisymposium stimulated those of us in attendance.

REFERENCES

1. Kidder HE, Casida LE, Grummer RH. Some effects of estrogen injections on the estrual cycle of gilts. J Anim Sci 1955; 14:470–474.[Abstract/Free Full Text]
2. Zavadovski MM, Wunder PA, Padueva AL, Margvelavili SG. Is it possible to control ovulation, estrus and the manifestation of heat in sheep? Trud Dinam Razvit 9:21–74 (Anim Breed Abstr 1935; 4:51).
3. Casida LE, Dutt RH, Meyer RK. Alteration of the estrual cycle by pituitary gonadotrophins and persistence of the effects upon reproductive performance in ewes. J Anim Sci 1945; 4:24–33.
4. Wiltbank JN, Casida LE. Alteration of ovarian activity by hysterectomy. J Anim Sci 1956; 15:134–140.[Abstract/Free Full Text]
5. Moore WW, Nalbandov AV. Neurogenic effects of uterine distension on the estrous cycle of the ewe. Endocrinology 1953; 53:1–11.[Medline]
6. Nalbandov AV, Moore WW, Norton HW. Further studies on the neurogenic control of the estrous cycle by uterine distension. Endocrinology 1955; 56:225–231.[Medline]
7. Stormshak F, Inskeep EK, Lynn JE, Pope AL, Casida LE. Progesterone levels in corpora lutea and ovarian effluent blood of the ewe. J Anim Sci 1963; 22:1021–1026.[Abstract/Free Full Text]
8. Tanabe TY. The role of progesterone during pregnancy in dairy cattle. Pennsylvania Agricultural Experiment Station Bulletin 1970; 774:1–61.

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