Vitellogenesis in the cockroach Nauphoeta cinerea: Separation of two classes of ovarian binding sites and calcium effects on binding and uptake
✍ Scribed by Dr. Rolf König; Helmut Kindle; Dr. Joseph G. Kunkel; Dr. Beatrice Lanzrein
- Publisher
- John Wiley and Sons
- Year
- 1988
- Tongue
- English
- Weight
- 965 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0739-4462
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✦ Synopsis
Two classes of vitellogenin binding sites with Kd-values of 7.3 n M and 290 n M were observed in follicle-membrane preparations of the cockroach Nauphoeta cinerea using a membrane-binding assay at pH 8. Separation of follicle cells and basal laminae from oocyte membranes prior t o binding studies showed that the fraction consisting of follicle cells and basal laminae (FC/BL) contained high-affinity binding sites for vitellogenin (Kd = 16.6 nM), whereas loweraffinity binding sites (& = 200 nM) were found in the oocyte membrane fraction. The concentration of Ca2+ had a distinct effect on vitellogenin binding and uptake: maximal binding to the oocyte membrane fraction was observed at 0.3 m M Ca2+ and to the FClBL fraction at 10 mM, whereas uptake of vitellogenin by oocytes in vitro was highest at 4 m M Ca2+. The calcium ionophore A23187 decreased vitellogenin uptake. This effect of A23187 could be counteracted by the calcium chelator Quin2. A hypothetical model for the uptake of vitellogenin into follicles of Nauphoeta cinerea is suggested.