ENVIRONMENTAL VERSUS FUNCTIONAL HYPOXIA ANOXIA IN SOLE SOLEA-SOLEA - THE LACTATE PARADOX REVISITED/

The effects of hypoxia (12 and 6% air saturation), anoxia and forced e xercise on intermediary metabolism were compared and the first 4 h of recovery after exhaustive exercise examined in common sole Solea solea . Intermediates of energy metabolism and lactate production were analy zed in white muscle, liver and blood. Rates of ATP production by anaer obic metabolism for the 4 different conditions were 52, 150, 1777, and 6834 pmol 100g(-1) h(-1), respectively. Total anaerobic ATP yield was 625, 1799, 3074, and 3132 mu mol ATP 100g(-1). Under hypoxia the ener gy consumption of the fish appeared to be depressed (i.e. below standa rd metabolic rate), while under anoxia the rate was at routine metabol ic rate, and under forced exercise was twice the active metabolic rate . The muscle/blood lactate ratio after forced exercise was comparable to those found previously for other flatfish species; however, hypoxia exposure resulted in a completely inverse situation with blood lactat e levels up to 20 mM, whereas anoxia resulted in an intermediate situa tion. The results challenge the present concept of lactate 'releasers' and 'non-releasers' describing the transfer of lactate from muscle ti ssue into the blood. It is concluded that the distinction between laca te 'releasers' and 'non-releasers' can no longer be applied on a speci es basis but must be related to type and intensity of the induced stre ss situation.