Disruption of Endocrine Regulation of Glycemia Levels by Cadmium and Copper in the Estuarine Crab Chasmagnathus granulata.

DANIEL A. MEDESANI, LAURA S. LÓPEZ G. AND ENRIQUE M. RODRÍGUEZ

BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY

SPRINGER SCIENCE

Año: 2004 vol. 73 p. 942 - 946

0007-4861

Carbohydrate metabolism has been one of the topics extensively studied in crustaceans (see Santos and Keller 1993a, for review). Hormonal control of circulating levels of glucose has also been one of the best-studied subjects in the field of crustacean endocrinology. The so-called “crustacean hyperglycemic hormone” (CHH) is a peptide of about 70 amino acids, that has been isolated and sequenced for several crustacean species (Keller 1992). It belongs to a family of neuropeptides, all of them released from the sinus gland in the eyestalks (Charmantier et al. 1997). Hyperglycemia in situations such as the emersion of crabs has been reported (Santos and Keller 1993b; Schmitt and Santos 1993) in correlation with increased levels of circulating CHH (Webster 1996). Since other stimuli promote CHH secretion, this hormone has been also proposed to act as a stress hormone for crustaceans (Chang et al. 1998, 1999). On the other hand, reproductive functions of some isoforms of CHH have been also reported and reviewed (Charmantier et al. 1997; De Kleijn and Van Herp 1998).   A hyperglycemic response has also been reported in crustaceans due to exposure to heavy metals such as cadmium (Reddy et al. 1994, 1996) and some other pollutants (Fingerman et al. 1998). However, a hypoglycemic dose-dependent effect was reported for the South American estuarine crab Chasmagnathus granulata after a 2-week exposure to cadmium and copper (Medesani et al. 2001). Hypoglycemia was seen in intact crabs, but not in eyestalkless ones. From these results, we proposed the hypothesis that the observed hypoglycemia was caused by both heavy metals through inhibition of CHH secretion from the eyestalks. However, an alternative hypothesis that those heavy metals antagonize the hormone action at target tissues merits investigation. This study is aimed therefore at testing this latter hypothesis.