Submitted March 25, 2004
Returned for revision April 11, 2004
Accepted May 27, 2004
Ovary
Characterization of Growth Hormone Binding Sites in
Granulosa and Theca Layers at Different Stages of
Follicular Maturation and
Ovulatory Cycle in the Domestic Hen
Irina Y. Lebedeva ,
Vladimir A. Lebedev ,
Roland Grossmann ,
Tatiana I. Kuzmina ,
and
Nahid Parvizi *
* To whom correspondence should be addressed. E-mail: parvizi{at}tzv.fal.de.
Abstract
The currently available evidence points to a possible
influence of GH on avian folliculogenesis, which can be
mediated by both hepatic- and ovarian-derived IGF-I.
Therefore, the purpose of the present study was to reveal
GH binding sites in granulosa and theca layers of
preovulatory follicles and to determine the binding
characteristics depending on the degree of follicular
maturation and the stage of the ovulatory cycle in the
hen. Hens were killed 2 h (stage I), 9 h (stage II), 16 h
(stage III), and 23 h (stage IV) after oviposition, and
the five largest yellow follicles (from F1 to F5) were
removed. Growth hormone (GH) binding sites in granulosa
and theca layers from F1-F5 follicles were
characterized
using a radioreceptor assay. Equilibrium dissociation
constants (Kd) and binding capacities (Bmax) were
determined by Scatchard analysis of saturation curves,
which revealed a single class of high affinity GH binding
sites in both theca tissue and granulosa cells. In F1, F2
and F5 follicles, Bmax and Kd for GH binding sites in the
granulosa layer changed during the ovulatory cycle,
decreasing between stages I and III to increase again at
stage IV, with alterations in Kd being less profound. No
significant differences in binding capacities and
affinities of GH binding sites in the theca layer were
found between various stages of the cycle. Furthermore,
the concentration of GH binding sites in the granulosa
layer rose, whereas that in the theca layer fell with
follicular enlargement. These findings indicate the
presence of high affinity GH binding sites in both
granulosa and theca layers of hen preovulatory follicles.
Data also demonstrate that GH binding sites in these
tissues are regulated in a tissue-specific manner.
Furthermore, the regulation of binding capacity of GH
binding in granulosa cells by hormonal factors associated
with ovulatory cycle is apparently not dependent to the
state of follicular maturation.
Key words:
Follicle •
Follicular development •
Granulosa cells •
Growth hormone •
Theca cells
