Synthesis of Progesteronein Vitroby Porcine Corpora Lutea1

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Abstract
Slices of porcine corpora lutea incubated in vitro incorporate acetate-1-14C into protesterone and 20[alpha]-hydroxy-4-pregnene-3-one. Progesterone-14C synthesis is greatest in tissues obtained from animals in midcycle or early pregnancy. Incubation of porcine luteal slices in the presence of LH [lutein-izing hormone] gives a significant increase (p< 0.001) in progesterone concentration above control levels. No significant difference between ovine, bovine, or porcine LH was seen. The mean values were: control 202, porcine LD 233, bovine LH 249, and ovine LH 245 [mu]g/g tissue, with approximately 50 flasks/treatment group. By using suitably increasing concentrations of LH (0.004-0.1 [mu]g/ml) a graded increase in progesterone concentration was obtained. Whereas progesterone synthesis in vitro is stimulated by LH (< 0.001), it is not influenced by FSH [follicle-stimulating hormone] or prolactin (values: control 200, LH 222, FSH 194, prolactin 196 [mu]g/g tissue; 36 flasks/treatment group). The increase in progesterone concentration induced by LH is greater in tissues obtained from sheep (30%) and cows (40%) than from pigs (15%). There is also greater variability in the measurements for procine luteal tissue, the percentage standard error being twice as large as it is for sheep and cows. It is suggested that the low increase in response to LH is due to deficient cholesterol stores which are shown to be much lower in pigs than has been reported for some other species, and the high variation is probably due to difficulties in sampling porcine luteal tissue.