Cytoplasmic Granules and Relaxin Levels in Porcine Corpora Lutea12

The fine structure of the porcine corpus luteum has been examined throughout pregnancy; levels of relaxin in luteal tissue were determined by biological assay at late stages of pregnancy. The appearance and accumulation of dense granules in the cytoplasm of granulosa luteal cells in early and midgestation and their disappearance in the last days of pregnancy paralleled closely the rise (1) and fall of relaxin in corpora lutea. This and other correlative evidence is interpreted as suggesting that the granules may contain relaxin. (Endocrinology89: 1, 1971)