The Fine Structure of Corpus Luteum from Intact, Hypophysectomized and Fetectomized Pregnant Monkeys (Macaca mulatta) at Term

The fine structure of granulosa lutein cells of the corpus luteum from pregnant monkeys (Macaca mulatta) is described. Corpora lutea were obtained within the span of expected normal delivery from intact mothers, as well as from mothers which were hypophysectomized (56-73 days), and those which were fetectomized (107-119 days) with the placentas maintained in situ until near expected time of delivery. The gramulosa luteim cells from all groups had fine structural characteristics indicative of active steroidogenesis. The slight differences in the fine structure of these granulosa cells involved factors of concentration and size, as well as appearance of several organelles. Cells of the corpus luteum from hypophysectomized animals had smaller mitochondria, often associated with lamellar structures, and microfilaments occurred more frequently than in intact animals. Mitochondria in the luteal cells from fetectomized monkeys with large osmiophilic inclusions were more numerous and agranular ER and Golgi were increased when compared to luteal cells from intact or hypophysectomized animals. Initial luteolysis was noticed in the CL of intact and hypophysectomized monkeys, but to a lesser extent in the fetectomized animals. Onset of luteolysis was indicated by obliteration of some blood vessels, shrinkage of cells and their nuclei, and distention of the cisternae of the granular endoplasmic reticulum. Dense fibrillar structures and collagen fibers accumulated in some of the perivascular and extracellular spaces. Various nexuses were formed at areas of contact of cellular projections and the cell surface in every group of monkeys. Fine structural features of CL from late pregnancy in rhesus monkeys support other evidence that these granulosa lutein cells are active in steroid synthesis.