 Illustrations of bihormonal granules
Bihormonal granules contain two hormones. The larger
gonadotropes may contain secretory granules that store both LH and FSH antigens as shown
in this figure. The detection system involved localizing both LH and FSH by sequential
immunolabeling. The small gold particles mark the site of LH (L) antigens and the large
gold particles mark the site of FSH (F) antigens. For more information about technology
see the cytochemistry web page.
Just before ovulation, there are more granules containing
only one of the hormones. These are called monohormonal granules. The changes during the
reproductive cycle are shown in the following graph. These data suggest that the
stimulation leading up to ovulation may cause sorting into separate vesicles by the Golgi
complex. Our future studies will test this hypothesis by stimulating gonadotropes and
following the sorting and packaging process. We will also block ovulation to learn if
stimulatory events cause the sorting process
This figure shows the results of
the counts of the monohormonal granules. We expressed the values as percentages of the
total granule population. The Y axis plots the changes in percentages with each stage of
the reproductive cycle. Key events in the reproductive cycle are noted on the X axis (each
point, however, is a different stage of the cycle).
Note that the levels of monohormonal LH granules are high
just before ovulation (and peak LH secretion). Then there is a drop as if they have been
secreted, preferentially. Levels of monohormonal FSH granules are also high before
ovulation because FSH is needed for this event. There is a drop followed by a rise as the
new crop of ovarian follicles mature. Illustrations of monohormonal LH and FSH granules
are shown in the following two figures.
Illustrations
of monohormonal granules
The Figure on the left illustrates FSH monohormonal granules found in gonadotropes early
in the cycle, just after ovulation. The granules are typically among the largest found in
gonadotropes. This the time when FSH stimulates the early development of the follicle and
these large monohormonal granules may be destined for this function. The FSH is labeled
with immunocytochemistry and 10 nm gold particles. One of the granules shows a 1-2 small
gold particles that label for LH antigens (L) (5 nm gold).
The Figure on the right illustrates LH monohormonal granules that predominate just before
ovulation. Note that the granules are smaller than the FSH monohormonal granules found
during follicular development. The LH antigens are labeled with small, 5 nm gold particles
(L). Two of the granules have 1-2 large gold particles marking sites of FSH antigens (F).
Thus, the Golgi complex sorting process is not always complete. Other granules (near the
top of the Figure) contain only LH antigens.
Monohormonal
packaging in the Golgi complex.
This figure shows the actual preferential packaging of LH antigens (L, marked
by small, 5 nm gold particles) in a condensing vacuole in the Golgi complex. At the bottom
left hand corner of the Figure are two large gold markers indicating a site for FSH
packaging (F). Future studies are designed to learn what factors promote this preferential
packaging. Obviously, as shown by evidence in the first figure, this sorting does not
always occur. At this time, we see it just before active secretion of one of the
gonadotropins or after stimulation by gonadotropin releasing hormone
Publications
discussing the above work.
Childs, G.V., Unabia, G.,
Tibolt, R. and Lloyd, J.M. Cytological factors that support non-parallel secretion of LH
and FSH during the estrous cycle. Endocrinology 121:1801-1813, 1987.
Childs, G.V. 1995 Division of
Labor among Gonadotropes, Vitamins and Hormones, 50: 217-283.
Protocols and related
web pages:
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situ hybridization Histochemistry | Go
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.Last updated: 06/04/01
URL Address: http://cellbio.uams.edu/childs/gon3.htm
Email: childsgwenv@uams.edu
© copyright 1995 Gwen V. Childs, Ph.D.
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