The effects of hydrostatic pressure on signal transduction in brain membranes of deep-sea fishes of the genus Coryphaenoides

To investigate the effects of increased hydrostatic pressure on transmembra ne signaling in deep-living marine species, the A(1) adenosine receptor - i nhibitory G protein (G(i)) - adenylyl cyclase signaling complex was examine d in brain membrane preparations from four teleost fish species of the deep -sea family Macrouridae. The combined depth ranges of the adults of these s pecies, Coryphaenoides armatus, C. cinereus, C. filifer, C. pectoralis, spa n several hundred meters to 5400 m. Basal adenylyl cyclase activity, determ ined at 5 degreesC, was inhibited by increased hydrostatic pressure in all four species. At the highest pressure tested, 476 atm, adenylyl cyclase act ivity was inhibited 60 to 70% relative to the atmospheric pressure values. Pressure inhibition did not result from denaturation or loss of protein com ponents from the membrane due to pressure-induced shedding. Despite the pre ssure-inhibition of basal adenylyl cyclase activity, the responsiveness of adenylyl cyclase activity to modulation by N-6-cyclopentyladenosine, an A(1 ) adenosine receptor agonist, was retained at elevated pressures. Because t he accumulation of the second messenger cAMP depends on the summation of mo dulatory inputs, these results indicate that the transmembrane signaling in these deep-living species is insensitive to hydrostatic pressure changes.