Dopaminergic regulation of ion transport in the crab Chasmagnathus granulatus

GENOVESE GRISELDA; MIHAELA SENEK; NICOLÁS ORTIZ; DAVID TOWLE; CARLOS LUQUET

San Diego, California.

Congreso; Experimental Biology 2005 and XXXV International Congress of Physiological Sciences.; 2005

Federation of American Societies for Experimental Biology - FASEB.

Euryhaline crabs compensate diffusive salt loss by active absorption across posterior gills, regulated by neuroendocrine factors such as dopamine (DA). In most species, DA stimulates electrogenic ion absorption via a cAMP pathway. We studied the effects of DA, DA receptor agonists and antagonists and effectors of the cAMP pathway in perfused gills of C. granulatus. DA dissolved in isosmotic saline produced a transient 120 % increase in the transepithelial potential difference (Vte). The PKA inhibitor KT5720 blocked this effect. Inhibition of phosphodiesterase or protein phosphatases blocked the descending phase of the effect, maintaining the increased Vte. DA applied to gills stimulated with the adenyl cyclase activator forskolin partially reduced Vte. To test whether stimulatory and inhihibitory effects of DA were mediated by different receptors, we perfused DA along with one D1 and two D2 receptor antagonists, SCH23390, Domperidone and Spiperone, respectively. SCH23390 blocked the inhibitory phase of DA effect, while both D2 antagonists blocked the stimulating phase. Similarly, the D1 agonist Fenoldopam, applied on gills stimulated with forskolin, produced the same reduction of Vte as DA. We propose that in C. granulatus D1-like receptors are linked to a Gi protein since they reduce the activity of the cAMP pathway. In contrast, D2-like receptors activate ion transport through a Gs protein increasing cAMP content.