Insulin binding sites in gills of the estuarine crabChasmagnathus granulata

✍ Scribed by Kucharski, Luiz Carlos; Ribeiro, Maria Flávia; Schein, Vanessa; Da Silva, Roselis S. M.; Marques, Maria

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 103 KB
• Volume: 279
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/(sici)1097-010x(19971001)279:2<118::aid-jez2>3.0.co;2-r

✦ Synopsis

Bovine 125 I-insulin was injected into the estuarine crab Chasmagnathus granulata in order to study its distribution and specific uptake by tissues. The highest radioactivity uptake occurred in both anterior and posterior gills, which reached maximum values at 30-60 min following labeled insulin administration. Heart and hepatopancreas concentrated a very low amount of radioactivity (only 9 and 3%, respectively, of that shown by gills). A significant reduction of the uptake was observed in the gills when an excess of unlabeled insulin was injected together with the labeled hormone. In vitro studies also showed specific uptake of 125 I-insulin by the gills incubated at 25°C, which reached a plateau after 120-min incubation, suggesting a saturable process. The inhibition of 125 I-insulin uptake was dose dependent on unlabeled insulin. Glucagon did not compete with radioactivity uptake by gills in vivo and in vitro. Further characterization of insulinbinding sites was performed in gill membrane. The amount of unlabeled insulin that prevented 50% of the 125 I-insulin uptake was 7.78 µg/ml, and the Scatchard plot analysis established the presence of binding site with Kd of 3.11 µM and Bmax of 0.14 µM (r = 0.99). Ovine prolactin was not able to prevent 125 I-insulin binding to gill membrane. These findings seem to indicate the presence of specific binding sites for insulin or insulin-like substance in crab gills, which deserves further studies.