Involvement of cAMP-Dependent protein kinase and intracellular free calcium ions in regulation of ovulation of the follicle-enclosed oocytes ofRana temporaria by gonadotropic hormones

The inhibitor of cAMP-dependent protein kinase N-[2-(methylamino)ethyl]-5-isoquinoline-sulfonamide (H-8) (12.5–50 μM) decreased the rate of ovulation of the follicle-enclosedRana temporaria oocytes induced by the homologous pituitary extract in amphibian Ringer solution and in a chloride-free medium. The inhibitor of voltage-dependent calcium channels diltiazem (10 and 100 μM) decreased the rate of ovulation in Ringer solution but did not affect it in a chloride-free medium or decreased the ovulation inhibitory effect of this medium. It was concluded that cAMP-dependent protein kinase and intracellular free calcium ions were involved as second messengers in the gonadotropin regulation not only in maturation of amphibian oocytes but also in ovulation.     

Influence of culture medium osmolality on maturation and ovulation of common frog oocytes stimulated in vitro by pituitary extract or progesterone

The influence of diluted Ringer solution on ovulation and maturation of common frog oocytes stimulated in vitro by homologous pituitary extract (0.005 pit/ml) or progesterone (1 μg/ml) was studied. During hibernation, the dilution of Ringer solution led to a decreased percentage of oocytes ovulated and matured under the influence of both inducers. As the season of reproduction approached, the dependence of oocyte maturation and ovulation on the Ringer solution dilution was reduced. Possible causes of different dependence of the ovulation of amphibian and sturgeon oocytes stimulated by gonadotropic hormones or progesterone on the culture medium osmolality is discussed.     

Aquaporins in gametogenesis of vertebrate animals

A review of the data on the presence, localization, and supposed role of aquaporin water channels in oocytes of Xenopus laevis, oogenesis and maturation of teleosts Sparus auratus and Oncorhynchus mykiss, oogenesis and oocyte maturation of rats and mice, and spermatogenesis of several mammalians.     

Oocyte maturation and activation in the common frog and the clawed toad under the action of divalent cations]

Maturation of Rana temporaria and Xenopus laevis oocytes was induced by solutions containing Mn2+ and Co2+ ions. Completion of oocyte maturation was estimated by the following criteria: (1) appearance of the maturation promoting factor (MPF) in the oocyte cytoplasm and (2) oocyte capacity to activation and formation of male pronuclei from the injected sperm nuclei. X. laevis oocytes matured under the effect of Co2+ ions were shown to contain MPF. Oocytes of both species matured under the effect of either ions could not be activated by pricking with a needle and injected sperm nuclei didn't transform into pronuclei. R. temporaria oocytes matured under the effect of ions in late spring, when natural spawning takes place, showed spontaneous activation.     

Influence of culture medium osmolality on maturation and ovulation of Rana temporaria oocytes stimulated in vitro by the pituitary gland extract or progesterone

The influence of diluted Ringer solution on ovulation and maturation of common frog oocytes stimulated in vitro by homologous pituitary extract (0.005 pit/ml) or progesterone (1 pg/ml) was studied. During wintering, the dilution of Ringer solution led to a decreased percentage of oocytes ovulated and matured under the influence of both inducers. As the season of reproduction approached, the dependence of oocyte maturation and ovulation on the Ringer solution dilution weakened. Possible causes of different dependence of the ovulation of amphibian and sturgeon oocytes stimulated by gonadotropic hormones or progesterone on the culture medium osmolality is discussed.     

Role of hydration in ovulation of common frog oocytes in vitro

Stimulation of ovulation of the common frog Rana temporaria oocytes with homologous pituitary extract caused an increase in their volume. Factors that are known to inhibit hydration in teleostean oocytes (potassium-free Ringer solution and inhibitor of Na⁺,K⁺-ATPase—ouabain), as well as aquaporin inhibitors (mercuric chloride and methylmethanethiosulphonate) inhibited also homologous pituitary extract-induced volume increase in follicle-enclosed oocytes and led to reduced percentage of ovulated oocytes. Volume of denuded oocytes remained unchanged in the course of maturation when exposed to progesterone or other treatments. The data obtained suggest that stimulation of oocyte ovulation in the common frog caused an increase in their hydration that is necessary for their ovulation but this did not occur in denuded cells.