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Journal of Experimental Biology 159,23-43 (1991)
Published by Company of Biologists 1991

The Effects of Hydrostatic Pressure on A1 Adenosine Receptor Signal Transduction in Brain Membranes of Two Congeneric Marine Fishes

JOSEPH F. SIEBENALLER 1, ARTHUR F. HAGAR 2, and THOMAS F. MURRAY 3

1 Deparment of Zoology and Physiology, Louisiana State University, Baton Rouge, LA 70803, USA
2 Department of Physiology, Louisiana State University Medical Center, New Orleans, LA 70122, USA
3 College of Pharmacy, Oregon State University, Corvallis, OR 97331, USA

To investigate the effects of deep-sea temperatures and hydrostatic pressures on transmembrane signal transduction, the A1 adenosine receptor/inhibitory G protein/adenylyl cyclase complex was studied in brain membranes from two congeneric marine fishes that live at different depths. These scorpaenid species, Sebastolobus alascanus and S. altivelis, have been used as a model system to study adaptations to the deep sea. At 5°C and atmospheric pressure the basal adenylyl cyclase activities of the two species are similar. The inhibition of adenylyl cyclase by the A1 adenosine receptor-specific agonist, N6-cyclopentyladenosine (CPA), was dependent on GTP. The IC50 values for inhibition of adenylyl cyclase by CPA were 2.0±1.14µmoll-1 and 1.6±1.06 for S. alascanus and S. altivelis, respectively. The A1 adenosine receptor antagonist 8-cyclopentyl-1, 3-dipropylxanthine reversed the CPA-induced inhibition of adenylyl cyclase in a concentration-dependent manner. Brain membranes prepared from the Sebastolobus species incubated at 48.1 MPa (0.1 MPa = l atmosphere) and 5°C for 2.5 h did not lose basal adenylyl cyclase activity or sensitivity to inhibition by CPA when assayed at atmospheric pressure. In contrast, rat brain membranes lost 59% of their activity under these conditions. At atmospheric pressure, the Km values of 2-deoxy-ATP were identical for the Sebastolobus species adenylyl cyclases. Increased pressure increased the Km values in both species. However, the Km of 2-deoxy-ATP was less sensitive to pressure for the enzyme from the deeper-living S. altivelis. Basal adenylyl cyclase activity and the inhibitory effect of 100µmoll-1 CPA were assayed at 0.1, 13.7 and 41.2MPa. Increased pressure inhibited basal adenylyl

Key words: A1 adenosine receptor, adenylyl cyclase, hydrostatic pressure, Sebastolobus altivelis, Sebastolobus alascanus, deep sea, brain membrane composition, ADP ribosylation

Accepted on April 5, 1991






© The Company of Biologists Ltd 1991