Masters Theses

Date of Award

12-1983

Degree Type

Thesis

Degree Name

Master of Science

Major

Zoology

Major Professor

John H. Abel

Committee Members

T. Chen, H. Kattesh

Abstract

Luteolysis has been characterized by functional alterations in the luteal cell such OS a decrease in progesterone secretion accompanied by a loss of available LH receptors both of which appear to precede major changes in the luteal cell ultrastructure. Sufficient data do not exist to pin-point the exact mechanisms responsible for regression, and thus the factors controlling the processes are still a mystery.

Prostaglandin F two-alpha (PGP 2-alpha) from the uterine endometrium has been shown to be a potent luteolytic agent on the ovary in many species including the rodent. In order to define systematically the ultrastructural changes in spontaneous and PGP 2 alpha-induced luteolysis in PMSG/hCG-primed immature rats, this study was undertaken. Rats were administered PGP 2- alpha on the sixth day of PMSG/hCG induced pseudopregnancy. Serum progesterone concentrations, specific binding of LH to ovarian homogenates and ultrastructural changes in the luteal cell were examined. Progesterone levels in serum were seen to decline by 73% within 24 hours following PGP 2-alpha administration, however, it increased and reached a peak by day 4 before declining to below control values for the duration of the study. Specific binding of LH/hCG to ovarian homogenates was 35% of control levels at 48 hours post-treatment. However, it rose to values comparable to that of controls by day 4 before declining in parallel to controls. Ultrastructural alterations were not observed until after day 6 post-treatment when luteal cells showed definite signs of regression such as subcellular disorganization and disruption, lysosome accumulation and reduction in cell size, all of which continued for the duration of the study. Thus, when pseudopregnant rots were treated with a single 1 mg dose of PGF 2-Glpha, iuteolytic affects such as reduction in serum progesterone concentrations were initially detected and was succeeded by declines in specific binding of LH/hCG to ovarian homogenates as well as changes in the ultrastructure of the luteal cell. The onset and intensity of luteolysis appeared to be more pronounced otter treatment with PGF 2-alpha than in controls.

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