Effect of different gonadal states on the forskolin stimulated adenylate cyclase activity in rat brain

Forskolin-stimulated adenylate cyclase activity, measured in the hypothalamus and cerebral cortex differs in male and female rats. The gonadal steroid treatment performed induced changes in the studied adenylate cyclase activity probably in relation to the sex of the animals. The stimulated-forskolin adenylate cyclase activity in the hypothalamus from orchidectomized males showed more sensitivity than ovariectomized females. Finally, in male rats, the effects of castration on the hypothalamic enzymatic activity were partially restored by the administration of testosterone dipropionate. On the other hand, estradiol decreased the forskolin-adenylate cyclase activity in the female hypothalamus and cerebral cortex. The results show that the forskolin-stimulated adenylate cyclase activity may be related with the sex and/or the gonadal state of experimental animals.

Guanylate cyclase activity in retina optic nerve and optic chiasm of rats under different illumination conditions

In the present work we have measured the guanylase cyclase activity in soluble fractions from several tissues relevant to the visual response under different illumination conditions. Guanylate cyclase was sensitive to changes of light / dark periods in incubated extract obtained from soluble fractions of retina, optic nerve and optic chiasm. The changes in soluble guanylate cylcase activity found, about 100 fold between dark and light periods in those tissues, indicate a key role for this enzyme. The results showed that light inhibit strongly the soluble retinal guanylate cyclase activity; while it increases the activity of this enzyme in the optic nerve. A generalized photoinhibited response of soluble guanylate cyclase eas observed in all studied tissues in prolonged dark adapted animals. The effect of Na+ 1 and 10 nM, and free Ca++ 28 M and 2.8 MuM on the guanylate cyclase activity was performed in the studied tissues. The enzymatic activity appeared to be inversely related in the retina and optic nerve with regard to the ion exposue, which may involve different ionic control mechanisms. All indicate an active role for the soluble guanylate cyclase in the phototransduction process not only in retina, also in other tissues relevant in the visual response.

Preparation, production and functional characterization of anti cAMP and cGMP antibodies

The present work was intended to evaluate the preparation of antigens, as well as the production and characterization of anti cAMP and cGMP antibodies. Such antibodies were obtained from rabbits, and we used 2'O-succinyl cyclic nucleotide derivate, conjugated with human serum albumin, as antigen. The characterization of the antibodies was monitored by their immunoreactivity with the labelled antigen [125I]-cyclic nucleotide. This assay consists in a competition between a labelled and an unlabelled antigen for a fixed number of binding sites present in the specific antibody. The antibodies were specific for the inducing antigens. Cross-reactivity tests showed low degree competition between the immunogen and other antigens. The very high affinity, high quality and specificity of the generated antibodies indicate that they may be used not only in radioimmunoassay and immunocytochemistry methodologies, but also as bioblockers of physiological pathways

Effect of progesterone on the hypothalamic cAMP concentration in estradiol: primed rats

El efecto de progesterona sobre la concentración de 3', 5' monofosfato cíclico de adenosina (cAMP) fue estudiado en el hipotálamo de ratas ovariectomizadas tratadas con estradiol. La inyección de progesterona (2mg/rata) en ratas ovariectomizadas, 3 días luego de la dosis de estradiol, produjo a la 4 h un aumento en el contenido hipotálamo del nucleótido: mientras que bajos niveles de cAMP se encontraron 24h después de la inyección de progesterona, lo cual sugiere una respuesta bifásica de la misma. La administración de dietilditiocarbamato, un bloqueante de la síntesis noradrenérgica, no previno el aumento de cAMP hipotalámico inducido por progesterona luego de 4 h de inyectada, el cual fue bloqueado por la administración de fenoxibenzamina, un a-adrenobloqueante, o propranolol, un ß-adrenobloqueante, suguiriendo la participación de receptores a y ß adrenérgicos. Puesto que no se obdervan cambios en la concentración hipotalámica de cAMP en los animales sacrificados por la tarde, se puede inferir que los efectos de progesterona sobre este parámetro podrían depender de la hora del día en que el esteroide fue administrado