Steroid Release in Vitro by Two Luteal Cell Types in the Corpus Luteum of the Pregnant Sow

Abstract

Corpora lutea from sows at 30, 60 and 90 days of gestation were dissociated enzymically, and the components of the resulting cell suspension were separated by sedimentation at unit gravity. Two luteal cell populations of 30-50 micronm diameter and 15-20 micronm diameter were obtained and superfused for up to 18 h with Dulbecco's modified Eagle medium, the cells being supported in a column in a matrix of Biogel. Fractions were collected every 30 min and assayed for progesterone and oestradiol-17beta. At 30 and 60 days of gestation the large luteal cells produced progesterone at an initial rate of approximately 100 ng/h/10(5) cells, which decreased to half this rate at 90 days. The smaller cells also released progesterone into the medium at approximately 15-20 ng/h/10(5) cells at all stages of gestation. At 30 days of gestation, neither cell type released significant amounts of oestradiol-17beta, but from 60 days onwards ,significant and increasing quantities were measured in the superfusates from the larger cells. Both cell types were perfused with porcine LH at the three stages of gestation, and both showed an immediate response in terms of progesterone release which decreased in magnitude with increasing age of gestation. The response of the smaller cells was greater than that of the larger cells.

Synergistic effects of insulin-like growth factor I and gonadotrophins on relaxin and progesterone secretion by ageing corpora lutea of pigs

“…Results from dispersed monolayers of luteal cells in culture indicate that prolactin and LH increase the rates of relaxin and progesterone secretion (Grinwich et al, 1983;Huang et al, 1991). Porcine luteal cells have prolactin-specific binding receptors (Rolland et al, 1976;Bramley & Menzies, 1987) and LH can stimulate progesterone secretion by these cells from the oestrous cycle and early pregnancy (Lemon & Loir, 1977;Hunter, 1981;Kineman & Rampacek, 1987), which is consistent with the present findings with ageing corpora lutea.…”

Effect of pregnancy, injection of oestradiol benzoate or hCG on steroid concentration and release by pig luteal cells

“…Similar observations have been made for the cow (Lukaszewska, 1980), rabbit (Hilliard et al, 1974), rat (Sridaran et al, 1981), pregnant pig (Grazul et al, 1987) and non-pregnant pig (Przala et al, 1984a). The high testosterone content of the luteal tissue may indicate that testosterone is stored in case it is required to synthesize a large amount of oestrogens by the corpus luteum (Lemon & Loir, 1977;Watson & Patek, 1979;Przala et al, 1984a), which can have a local effect by increasing progesterone secretion (Gregoraszczuk, 1983). On the other hand it seems more likely that oestro¬ gens are released into the plasma or changed into oestrone (Robertson et al, 1978) rather than accumulated by the corpus luteum during early pregnancy.…”

Identification of relaxins in porcine follicular fluid and in the ovary of the immature sow

“…During pregnancy the corpus luteum must reach a certain age before synthesis and/or secretion of relaxin can take place (Sherwood, Martin, Chang & Dziuk, 1977). Lemon & Loir (1977) (Frieden & Yeh, 1977) and species of 19 000, 13 000 and 10 000 molecular weight have been extracted from fresh pregnant sow corpora lutea ( wok, Chamley & Bryant-Greenwood, 1978).…”