Effects of estradiol-17beta and 17alpha, 20beta-dihydroxy-4-pregnen-3-one on different phospholipids metabolism and histological changes in ovary during reproductive growth in the catfish, Heteropneustes fossilis (Bloch).

Effect of cumulative doses of estradiol -17beta (E2-7, 14 and 28 mg/kg body weight) and 17alpha, 20beta-dihydroxy-4-pregnen-3-one (17alpha,20betaP-7, 14 and 28 mg/kg body weight) on total phospholipids (TP) and various phospholipids- phosphatidylcholine (PC), phosphatidylserine (PS), phosphatidylinositol (PI) and phosphatidylethanolamine (PE) on liver plasma and ovary were investigated during the reproductively active preparatory and prespawning phases of the annual reproductive cycle in the freshwater female catfish, H. fossilis. The effect of E2 on TP was generally stimulatory and has pronounced effect than 17alpha,20betaP during both the phases. The levels of PC was promoted high during prespawning phase by E2 comparatively very less than by 17alpha, 20betaP in studied tissues during both the phases. The levels of PS after E2 treatments was maximum in all tissues during prespawning phase whereas 17alpha,20betaP was effective only in liver during this phase. The PI was elevated in liver during preparatory phase but its elevation was in all studied tissues during prespawning phase after E2 treatments. The levels of PI was most effective in ovary during preparatory phase in response to 17alpha,20betaP. The levels of PE was declined in liver but elevated in ovary after E2 treatments during both the phases. Treatments of E2 during preparatory phase showed greater number of vitellogenic oocytes as compared to 17alpha,20betaP treatments. The present finding has demonstrated that estradiol-17beta has more pronounced effects than the 17alpha,20beta P in regulation of different phospholipids and ovarian recrudescence during reproductively active phases and among the phospholipids the PC is the main phospholipids of vitellogenin/ovarian lipids in H. fossilis.

Insulin alone can lead to a withdrawal of meiotic arrest in the carp oocyte.

Meiotic arrest of oocyte in an Indian carp, Labeo rohita Ham. has been found for the first time to be withdrawn by insulin only. Addition of insulin to oocytes in vitro caused germinal vesicle breakdown (GVBD), one of the first visual markers to determine initiation of the final maturational process. Under the influence of insulin the germinal vesicle (GV) of the oocyte migrated towards the animal pole, reached the micropyle and then dissolved (GVBD). By using different concentrations of insulin i.e., 0.063, 0.63, 6.3 and 12.6 mM, optimum amount required was found to be 6.3 mM. Induction of GVBD by insulin could be blocked by cycloheximide (Chx), a translation inhibitor, while actinomycin D (AcD) had no effect suggesting non-involvement of transcriptional activity in this process. Addition of the maturation-inducing steroid 17alpha,20beta-dihydroxy-4-pregnen-3-one (DHP) stimulated (P<0.01) GVBD of carp oocytes and its combination with insulin showed an additive effect. Gonadotropin (GtH) caused GVBD but its effect was greatly augmented by insulin. Our results demonstrate that not only can insulin alone induce GVBD in carp oocytes, but it also augments the stimulatory effect of DHP or IGF-I or GtH on GVBD. This information will be important in hormonal manipulation during induced breeding of carp.

Cyclic AMP-mediated control of oocyte maturation in the catfish, Clarias batrachus (Bloch): effects of 17 alpha,20 beta-dihydroxy-4-pregnen-3-one and phosphodiesterase inhibitors.

An increase in the percentage of germinal vesicle breakdown (GVBD) with a corresponding decrease in cAMP was found in the oocytes which were incubated for 36 hr with different concentrations of 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-DP). At its highest concentration (1 microgram/ml), 17 alpha,20 beta-DP induced 91.9 +/- 2.3% GVBD and decreased cAMP level to 0.8 +/- 0.1 pmol/oocyte from 2.9 +/- 0.2 pmol/oocyte (control). The two different known inhibitors of phosphodiesterase viz. 3-isobutyl-1-methyl-xanthine (IBMX) and theophylline inhibited GVBD in vitro and promoted the accumulation of cAMP in a dose-dependent manner irrespective of whether the oocytes were treated for a short duration (2 hr) or for a long duration (36 hr). Evaluation of time course response to 1 mM IBMX or 1 mM theophylline revealed that cAMP levels increased at all the time points when compared with their respective controls and blocked maturation. In contrast, 1 microgram/ml 17 alpha,20 beta-DP not only induced oocyte maturation but also caused an immediate decrease in cAMP within the first 2 hr (from 3.2 +/- 1.3 to 1.3 +/- 0.1 pmol/oocyte) of incubation which was maintained till the end of experiment (36 hr). Likewise, a significant inhibition of GVBD and accumulation of cAMP was recorded even in oocytes pre-stimulated with 1 microgram/ml 17 alpha,20 beta-DP for 6 hr and then treated with different concentrations of IBMX or theophylline. Taken together, these data strongly suggest that in C. batrachus a decrease of oocyte cAMP concentration is a prerequisite for the induction of oocyte maturation, and its increase is associated with the maintenance of meiotic arrest.

Effect of 11 beta OH pregna-1,4-diene-3,20-dione (deltaHOP) on thymocyte plasma membranes

En trabajos anteriores se demostró que la acción inibitoria del esteroide delta HOP a altas concentraciones no era consecuencia de un efecto genómico como en el caso de los glucocorticoides. Para investigar si este efecto se producía a traves de la membrana plasmática, en este trabajo se estudió , en tromocitos de ratas, las alteraciones producidas por estos esteroides en la fuidez de la membrana por polarización de fluorescencia con 1,6-difenil-1, 3, 5-hexatrieno (DPH) y la movilidad de las proteínas de susperficie por la formación de "caps" con concanavalina A fluorescente (Con A-fl). La polarización de fluorescencia disminuyó con los glucocorticoides por aumento de la fluidez de la membrana, mientras que la alfa HOP no produjo ningún cambio. En los experimentos con Con A-fl se observó una disminución del inúmero de células con "cap" cuando se incubó con delta HOP y con los inhibidores de "caps" (citocalasina B y acida sódica), mientras que los glucocorticoides no tuvieron efecto inhibidor. El tratamiento "in vitro" con delta HOP o glucocorticoides produjo el mismo efecto que "in vitro". Estos resultados sugieren que la delta HOP actúa en forma superficial sobre la membrana plasmática, in hibiendo la movilidad de las proteínas de superficie, pero no alterando la fluidez de la bicapa lipídica

Appearance and persistence of 113-hydroxypregnant-1, 4-diene-3, 20-dione (delta HOP) effect in vivo

Se estudió el efecto "in vitro" de la 11ß-hidroxipregna-1,4-diene-3,20 diona (DeltaHOP) en ratones tratados en forma aguda y crónica con el esteroide, en conparación con los tratados con dexametasona y vehículo. En los experimentos agudos, una inyección de DeltaHOP de 2 mg/100 gm de peso animal tuvo su máximo efecto inhibitorio en la incorporación de uridina-H3 por los timocitos después de 18 h, desapareciendo el efecto a las 36 h, no observándose cambios en los niveles de corticosterona plasmática. Una dosis de 0.033 mg/100 gm de peso animal de dexametasona produjo inhibición en la incorporación de uridina 5 h después de la inyección, juntamente con una disminución significativa de los niveles de corticosterona plasmática; este efecto desapereció a las 12 h, mientras que el ejercido sobre el timo recién desapareció a las 24 h. En el tratamiento crónico DeltaHOP produjo la máxima inhibición 5 h después de la última inyección y se mantuvo hasta las 36 h sin modificar la corticosterona plasmática. En cambio la dexametasona produjo la misma inhibición que DeltaHOP, pero el efecto desapareció antes ( a las 18 h); en estos animales la corticosterona se mantuvo baja hasta las 18 h. En tratamientos crónicos, después de 5 h de la última inyección, DeltaHOP no modificó los pesos de timos y bazos, pero éstos disminuyeron significativamente con el tratamiento de dexametasona. Estos resultados sugieren que la acción "in vivo" de DeltaHOP es diferente a la de los glucocorticoides

Mechanism of the inhibitory effect of 11ß hydroxypregna 1,4 diene 3,20 dione (delta HOP) at high concentrations in RNA synthesis / 303-12

La potente inhibición de la síntesis de ARN en timocitos de rata por la 11ß -hidroxipregna-1,4-dien-3,20-diona (DeltaHOP) demostrado recientemente, cumple las tres condiciones requeridas para un efecto no-genómico: no perdurabilidad del efecto después de ser retirado el esteroide por lavado, acción instantánea y efecto en presencia de inhibidores de la síntesis de ARN. La inyección intraperitoneal de DeltaHOP en ratones (2 mg/100 gm) provoca un 32% de inhibición de la síntesis de ARN en los timocitos; queda por aclarar si esta inhibición es debida también a un efecto no-genómico