MEDESANI, D.A.; L�PEZ GRECO, L.S.; RODR�GUEZ, E.M.; University of Buenos Aires, Argentina: Interference of heavy metals on endocrine control of ovarian growth, in the estuarine crab Chasmagnathus granulata
The effects of cadmium and copper on the hormonal control of ovarian growth were evaluated on the estuarine crab Chasmagnathus granulata, by means of both in vivo (14 d-exposure) and in vitro (24 h) assays. For both kind of assays, heavy metal (HM) concentrations of 0 (control), 0.5 mg/L of cadmium or 0.1 mg/l of copper were used. No significant (p>0.05) change of the gonadosomatic index was observed in the in vivo assays with intact females exposed to HM, while eyestalk-ablated exposed females showed significantly (p<0.05) lower GSI values than their respective controls. This latter result led us to consider the possibility that the HM interfered with extra-eyestalk hormones. In this sense, no differences were noted between control and HM exposed groups after co-incubating ovary with thoracic ganglion (the source of the gonad stimulating hormone). However, when ovary was incubated with methyl farnesoate or 17-hydroxyprogesterone, 3H-leucine incorporation was significantly lower in the HM-exposed groups than in the controls, indicating a possible interference of cadmium and copper with the transduction pathway of those hormones. On the other hand, ovaries co-incubated in vitro with eyestalk tissue (ET) and exposed to either HM, showed significantly higher 3H-leucine incorporation than did the controls. Taking also into account that the addition of eyestalk extracts to the incubation medium reversed the effect caused by each HM, an inhibitory effect of the assayed HM on the secretion of the gonad inhibiting hormone (GIH) from the ET seems to have occured.
