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.
ABSTRACT
The effect of estradiol–17ß and progesterone given separately as well as in combination on the rate of hydrogen peroxide formation and lipid peroxidation in the uteri of ovariectomized rats was studied. Estradiol in 3 μg dose per day per animal elicited maximum stimulatory response and progesterone (100 μg), on the other hand, was without any such effect. However, progesterone given along with estradiol completely prevented the effect due to the latter. In the same way, vitamin E, a well known antioxidant was found to be extremelv effective in protecting the uterus from the highly peroxidative action of estradiol–17ß.
ABSTRACT
Prostaglandin-synthetase activity has been measured in the microsomal fraction of developing toad (Bufo melanostictus) ovary using arachidonic acid as the substrate. Indomethacin (0·74 μΜ) and aspirin (0·35 μΜ) inhibit this activity. The activity is maximum in immature ovary and its level gradually decreases with maturity of the organ till the breeding season arrives, when it rises again. Time course study shows that the activity in vitro becomes steady after 3 min of incubation in all the cases, except the immature ones in which it sharply declines. Soluble supernatant was found to contain some inhibitory factor(s), which is partially inactivated by heating at 100°C for 5 min (~ 43%). Intraperitoneal injection of equine luteinizing hormone stimulates this enzyme activity in the mature ovary during non-breeding season. This suggests that similar to mammalians prostaglandin-synthetase, the toad ovary enzyme is also regulated by luteinizing hormone.