Biology of Reproduction, Vol 14, 458-472, Copyright © 1976 by Society for the Study of Reproduction

Luteolytic Effects of a Prostaglandin Analogue, Cloprostenol (ICI 80,996), in Rats: Ultrastructural and Biochemical Observations

¹ Department of Pathology, Magee-Womens Hospital, University of Pittsburgh Medical School, Pittsburgh, Pennsylvania and Biology Department, Imperial Chemical Industries Limited, Pharmaceuticals Division, Macclesfield, Cheshire, England

Pregnant rats were treated at Day 7 of gestation with a single intravaginal dose of 25 µg of a prostaglandin analogue, cloprostenol (ICI 80, 996) to study effects on luteal structure and function. Morphological alterations at the subcellular level were found as early as 3 h posttreatment, consisting of increased numbers of mitochondria and cristae, dispersion and reduction in the size of the SER vesicles, decreased RER cisternae, and slight increase in lipid inclusions. Further alterations were more progressively apparent between 6 and 26 h, represented predominantly by changes in the cristac arrangement, shape and appearance of mitochondria, further disorganization of the SER, cytoplasmic vacuolization, accumulation of lipid inclusions and increased lysosomal activity. Some cells appeared totally destroyed at 26 h posttreatment. Circulating levels of progesterone had dropped significantly by 6 h posttreatment and continued falling throughout the experiment. This ultrastructural-biochemical correlation indicates that the prostaglandin analogue has a direct, rapid and potent luteolytic effect in this species.

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