Mechanisms Controlling the Function and Life Span of the Corpus Luteum

Abstract

The primary function of the corpus luteum is secretion of the hormone progesterone, which is required for maintenance of normal pregnancy in mammals. The corpus luteum develops from residual follicular granulosal and thecal cells after ovulation. Luteinizing hormone (LH) from the anterior pituitary is important for normal development and function of the corpus luteum in most mammals, although growth hormone, prolactin, and estradiol also play a role in several species. The mature corpus luteum is composed of at least two steroidogenic cell types based on morphological and biochemical criteria and on the follicular source of origin. Small luteal cells appear to be of thecal cell origin and respond to LH with increased secretion of progesterone. LH directly stimulates the secretion of progesterone from small luteal cells via activation of the protein kinase A second messenger pathway. Large luteal cells are of granulosal cell origin and contain receptors for PGF(2alpha) and appear to mediate the luteolytic actions of this hormone. If pregnancy does not occur, the corpus luteum must regress to allow follicular growth and ovulation and the reproductive cycle begins again. Luteal regression is initiated by PGF(2alpha) of uterine origin in most subprimate species. The role played by PGF(2alpha) in primates remains controversial. In primates, if PGF(2alpha) plays a role in luteolysis, it appears to be of ovarian origin. The antisteroidogenic effects of PGF(2alpha) appear to be mediated by the protein kinase C second messenger pathway, whereas loss of luteal cells appears to follow an influx of calcium, activation of endonucleases, and an apoptotic form of cell death. If the female becomes pregnant, continued secretion of progesterone from the corpus luteum is required to provide an appropriate uterine environment for maintenance of pregnancy. The mechanisms whereby the pregnant uterus signals the corpus luteum that a conceptus is present varies from secretion of a chorionic gonadotropin (primates and equids), to secretion of an antiluteolytic factor (domestic ruminants), and to a neuroendocrine reflex arc that modifies the secretory patterns of hormones from the anterior pituitary (most rodents).

Physiological and practical effects of progesterone on reproduction in dairy cattle

“…After prostaglandin F2α (PGF2α) treatment, there was an abrupt and dramatic decrease in 3βHSD mRNA abundance (35% of control concentrations at 4 h; 15% of control at 12 h). However, there is no decrease in protein for P450scc or in 3βHSD enzyme activity even at 24 h after PGF2α treatment (Hawkins et al, 1993;Juengel et al, 1998;Niswender et al, 2000; Atli et al, 2012). Given that circulating P4 is decreased by 12 h after PGF2α treatment it seems unlikely that inhibition of P450scc and 3βHSD are a critical part of the acute inhibition of P4 production during luteolysis.…”

“…Three oxidation steps are catalyzed by this enzyme: hydroxylations at the 20 and 22 positions and then cleavage between these two carbons. The mRNA and protein for P450scc dramatically increase in CL after the LH surge and luteinization Niswender et al, 2000). Pregnenolone has two hydrophilic residues that increase the mobility through cellular membranes.…”

A simple mathematical model of the bovine estrous cycle: Follicle development and endocrine interactions

“…The LH surge at the end of the third wave induces ovulation of the dominant follicle and differentiation of cells of the follicular wall into luteal cells [51]. Continued CL growth is stimulated by autocrine and paracrine mechanisms [68].…”

“…If pregnancy does not occur, regression of the CL is required to allow the next ovulation. CL regression is induced by pulsatile PGF2α secretion from the uterus [51]. In each cycle a new CL develops, but CL development is modeled as a continuous function of P4 producing tissue.…”

Função do interferon-tau durante o reconhecimento materno da gestação em ruminantes

“…Corpo lúteo e luteólise O CL é descrito como uma glândula temporária formada a partir de um folículo que ovulou, tendo como sua secreção primária a progesterona, esteroide necessário para a ciclicidade ovariana e o estabelecimento e manutenção da gestação na maioria dos mamíferos (MCCRACKEN et al, 1999;NISWENDER et al, 2000;DAVIS & RUEDA, 2002). No CL de ovinos, foram isolados e identificados dois tipos de células esteroidogênicas; as células grandes e as células pequenas, que podem ser identificadas mediante características morfológicas e bioquímicas (FITZ et al, 1982;NISWENDER et al, 1985).…”