Regulation of Luteal Function in Domestic Ruminants: New Concepts

KIT receptor-positive cells in the bovine corpus luteum are primarily theca-derived small luteal cells

“…This is in line with the literature describing lack of CYP17 expression in the bovine CL (Rodgers et al 1986, Conley et al 1995. Our observation revisits the discussion of whether small thecal cells remain small cells or alternately transform into large luteal cells (Niswender et al 1985(Niswender et al , 2000. The small KITC cells with a rather diffuse immunostaining might represent theca-derived cells and contribute to cell renewal in pregnancy.…”

“…Potentially, new luteal cells differentiate from CL precursor cells into luteal cells under the appropriate stimulus. Such a precursor concept was postulated years ago (Niswender et al 1985(Niswender et al , 2000, but the precursor cells have not yet been found. Because bone marrow precursor/progenitor cells are characterized by KIT expression (Li et al 2003, Fazel et al 2006, we undertook to determine the presence or absence of KITC cells in the bovine CL and whether changes in pattern are detectable during the estrous cycle and during pregnancy.…”

Differential regulation by LH and prostaglandins of steroidogenesis in small and large luteal cells of the ewe

“…Although small luteal cells outnumber large luteal cells, they comprise 17% of the volume of the corpus luteum, whereas large luteal cells make up 25-35% (Nett, McClellan & Niswender, 1976;Rodgers et al, 1984). At the ultrastructural level, both small and large luteal cells from the ewe have abundant agranular endoplasmic reticulum and numerous mitochondria (Niswender et al, 1985), features which are typical of active steroid-secreting cells (1982), and Gulyas (1984). It should be noted that some of the differences between small and large luteal cells vary with species.…”

“…Perhaps the most important factors involved in the regulation of progesterone secretion are luteinizing hormone (LH) and the prostaglandins. LH stimulates progesterone secretion by luteal tissue and can maintain luteal function in hypophysectomized animals (reviewed by Hansel, Concannon & Lukaszewska, 1973;Niswender, Schwall, Fitz, Farin & Sawyer, 1985). Prostaglandins (PG) F-2a and E-2 appear to have opposing effects.…”

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

“…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). As células luteais grandes secretam aproximadamente sete vezes mais progesterona, quando não estimuladas por agente luteotrófico, quando comparadas com as pequenas (KENNY et al, 1989).…”