Metabolic changes during spermatogenesis and thoracic tissue maturation in Drosophila hydei

Abstract

In vitro enzyme studies indicate that gametes depend upon carbohydrate oxidation by way of the pentose shunt cycle, glycolysis, and the Krebs cycle for energy early in spermatogenesis in Drosophila hydei. Enzymes associated with amino acid metabolism and fatty acid synthesis are also high in activity at these developmental stages. In late spermiogenesis gametic glycolytic and Krebs cycle enzyme activities increase greatly. Both carbohydrates and amino acids are likely energy sources for mature spermatozoa. Low lactate dehydrogenase and β-hydroxyacyl dehydrogenase activities suggest that gametes at all developmental stages have low capacities for lactic acid formation and fatty acid oxidation. Thoracic tissue development differs fundamentally from testis development in that the α-glycerophosphate dehydrogenase-oxidase cycle becomes highly developed in thoracic tissue, whereas the low activity of α-glycerophosphate dehydrogenase indicates that it is a minor factor in gamete metabolism. Furthermore, NADP-isocitrate dehydrogenase and malic enzyme become increasingly less active as thoracic tissue matures, with malate dehydrogenase and NAD-isocitrate dehydrogenase becoming more active. The NADP-dependent enzymes are very active at all stages of spermatozoan development. Glycolytic and Krebs cycle enzyme activities are much higher in thoracic tissue at all maturation stages than in the mature testis.