Modulation of adenyl cyclase activity in the gills of Tapes philippinarum.
Adenyl cyclase (AC) plays a pivotal role in cell signaling. The AC system of bivalves has received little attention so far, and our study has been addressed to the characterization of AC properties in the gills of T. philippinarum. The enzyme showed a Km value of 0.77 mM for ATP in the presence of 5 mM Mg2+; in the absence of agonists, it was poorly affected by GTP, while it was stimulated by GTPgammaS and GppNHp up to 14-fold and 4-fold, respectively. Similarly to other invertebrates, the enzyme activity was scarcely stimulated by forskolin. The receptor agonist serotonin (5-HT) significantly stimulated the AC activity, and the pharmacological profile of the 5-HT receptor/s was as follows: (+)butaclamol > dihydroergocryptine > methysergide > prazosin > yohimbine. The AC activity was assessed in vitro in the presence of tributyltin chloride and HgCl2, which reduced the AC activity only at the highest dose tested (10-100 microM). Our data indicate the presence of a membrane-bound AC in gill membranes of T. philippinarum, coupled to Gs proteins and to a specific class of 5-HT receptors. Such receptors show a pharmacological profile slightly different from that reported for 5-HT invertebrate receptors cloned so far.
Valbonesi
Paola
P
University of Bologna, Interdepartment Centre for Research on Environmental Science, 48100 Ravenna, Italy.
Caselli
Federico
F
Capuzzo
Antonio
A
Fabbri
Elena
E
D000262:Adenylyl Cyclases / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D049872:Bivalvia / Q000187:drug effects / Q000201:enzymology*; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000633:toxicity; D005880:Gills / Q000187:drug effects / Q000201:enzymology*; D007700:Kinetics; D008627:Mercuric Chloride / Q000633:toxicity; D011985:Receptors, Serotonin / Q000378:metabolism; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology*; D012701:Serotonin / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014220:Trialkyltin Compounds / Q000633:toxicity
D004785:Environmental Pollutants; D011985:Receptors, Serotonin; D014220:Trialkyltin Compounds; D012701:Serotonin; C011559:tributyltin; D008627:Mercuric Chloride; D000242:Cyclic AMP; D000262:Adenylyl Cyclases