Morphology of the regressing corpus luteum in the ewe.

Abstract

Ultrastructural features of the regressing corpus luteum have been studied in the ewe at the end of the estrous cycle. Luteal cells secrete densely-staining granules which have been reported to contain progesterone. This process appears to be maximal at Day 10 of the cycle and begins to taper off noticeably at Day 12. The secretory activity declines gradually till Day 14, but up to this time the fine structure of other cytoplasmic organdIes in the luteal cell shows no remarkable change, save for a gradual increase in the number of autophagocytic bodies which first begin to appear at Day 12. In contrast, on Day 15 there is evidence of marked degeneration; the luteal cells are shrunken, granule secretion has ceased, autophagocytic bodies are numerous and lipid droplets, rarely seen in the fully functional cell, are present in abundance, Lysosomes are observed at all stages of the cycle and there is no dramatic increase in their number towards the end, In some cells at Day 15 the process of degeneration has advanced to the stage where the fine structure of organelles is no longer recognizable and within autophagocytic bodies there are large sites associated with acid phosphatase activity.