| Abstrakt: |
Granulosa cells synthesize glycosaminoglycans (GAG) as constituents of proteoglycans. Those proteoglycans accumulate in follicular fluid because their molecular sizes exceed the molecular weight cut-off for the blood-follicle barrier. A proteoglycan containing heparan sulfate side-chains accounts for 10 to 15% of the total proteoglycans synthesized and secreted by granulosa cells and found in antral fluid. The majority (85 to 90%) of the GAG is dermatan sulfate existing on two proteoglycans which differ mainly by their number of dermatan sulfate chains. The smaller molecular weight dermatan sulfate proteoglycan varies in production in response to hormonal stimuli and its concentration in antral fluid decreases with follicular enlargement Potencies of the heparan sulfate and dermatan sulfate chains to interact with heparin binding sites on granulosa cells vary with follicular maturation Glycosaminoglycans modulate gonadotropin binding to granulosa cells; inhibit degradation of low density lipoproteins and progesterone production by granulosa cells; affect cumulus expansion, oocyte maturation, and physical properties of the zonae pellucidae; and are related to fertilizing quality of oocytes in vitro Thus, GAG serve to orchestrate a multitude of events which must act in concert for normal follicular development to proceed. Failure of a follicle to metabolize proteoglvcans in appropriate ratios at critical points during differentiation may lead to elevated concentrations of those proteoglycans and prevent ovulation Thus, proteoglycans/GAG may be a biochemical key to our understanding of cellular changes contributing to atresia. |
