Alteration of lipid composition, Na+, Κ+-ATPase and Δ5-3ß-hydroxy steroid dehydrogenase activities in microsomal membranes of mature toad ovary in different seasons.

ABSTRACT

Microsomal membranes isolated by sucrose density gradient centrifugation from mature toad ovary has been found to vary significantly in lipid composition and various enzyme activities in different seasons. Na+, Κ+-ATPase activity is the highest in breeding season (rainy season). Significantly the optimum temperature for enzyme activity is 30°C. The other enzyme Δ5-3ß-hydroxysteroid dehydrogenase activity is also lower in hibernation period than other seasons. The total phospholipid, sterol and fatty acid contents differ significantly between seasons. The poly-unsaturated fatty acid, except arachidonic acid content in hibernation period is much lower than that during other seasons. The sterol content is also the lowest in this season. The present findings indicate that during hibernation period the membrane is more rigid and the metabolic activity of the animal is slow because of a lower level of various functionally important enzyme activities.