Dynamic Features of Luteal Secretory Granules:Ultrastructural Changes during the Course of Pregnancy in the Cow*
- 1 October 1985
- journal article
- research article
- Published by The Endocrine Society in Endocrinology
- Vol. 117 (4) , 1675-1682
- https://doi.org/10.1210/endo-117-4-1675
Abstract
The ultrastructure of large and small cells from corpora lutea of pregnant cows (days 45-280) were evaluated by electron microscopy. The distinguishing features of small cells (10-15 .mu.m in diameter) included stacks of rough endoplasmic reticulum, whorls of smooth endoplasmic reticulum, elongated mitochondria containing crystalline-like inclusions, and cytoplasmic lipid droplets. The large cells (20-50 .mu.m in diameter) contained numerous mitochondria packed tightly together (no elongated structures), an abundance of smooth endoplasmic reticulum (no whorls), and a large number of membrane-bound secretory granules (150-300 nm in diameter). These granules appeared to be packaged in the Golgi, accumulated at a paranuclear region, and migrated as a group to the cell membrane where they were exocytosed. These granules were first observed on day 45 and increased in number to reach a peak around day 200. Lipid droplets became a common cytoplasmic inclusion in the large cells during the third trimester of pregnancy. In addition, during this stage, an electron-dense substance began to accumulate in the mitochondria to such an extent as to occlude the cristae. These mitochondria looked like large (500-1800 nm) membrane-bound granules; however, they did not undergo exocytosis. Their appearance in large cells during the last 3 months of pregnancy may reflect a change in steroid metabolism. Thus, there are two morphologically distinct cell types throughout pregnancy in the cow. The large cells containing the secretory granules underwent what appeared to be a progressive state of apparent deterioration with advancing pregnancy. The morphology of the small cell did not undergo such a dynamic change. No morphological evidence was observed that would support a transition state between the two cell types.This publication has 19 references indexed in Scilit:
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