[14-3-3 proteins--a role in the regulation of melatonin biosynthesis].

14-3-3 proteins compose a large family of proteins that exist primarily as homo- and heterodimers within all eukaryotic cells. They are engaged in the regulation of numerous cellular processes, including melatonin biosynthesis. Melatonin, the hormone of darkness, is synthesized in a diurnal or circadian rhythm, with high levels at night.

UV-A light regulation of arylalkylamine N-acetyltransferase activity in the chick pineal gland: role of cAMP and proteasomal proteolysis.

Acute exposure of dark-adapted, cultured chick pineal glands to UV-A light significantly decreased the tissue cAMP concentration and the activity of arylalkylamine N-acetyltransferase (AANAT), the penultimate and key regulatory enzyme in the melatonin biosynthetic pathway. The magnitude of these changes was dependent on the duration of UV-A exposure. The UV-A light-evoked decline in pineal AANAT activity was blocked by cAMP protagonists (forskolin and dibutyryl-cAMP) and by inhibitors of the proteasomal degradation pathway (MG-132, proteasome inhibitor I, and lactacystin).

Near-ultraviolet light perceived by the retina generates the signal suppressing melatonin synthesis in the chick pineal gland-an involvement of NMDA glutamate receptors.

Exposure of dark-adapted chicks to near ultraviolet (UV-A) light significantly decreased melatonin (MEL) content and the activity of serotonin N-acetyltransferase (AA-NAT; the penultimate and key regulatory enzyme in MEL production) in the pineal glands. Significant reduction in MEL level and AA-NAT activity was also found in pineals of animals whose heads were covered with black opaque tape, an observation suggesting that in the chicken UV-A light perceived by the eyes alone is capable of affecting MEL synthesis in the pineal gland. Covering the chick's eyes, in addition to the head, totally blocked the studied UV-A action.

Pertussis toxin-sensitive G protein modulates the ability of histamine to stimulate cAMP production in the chick pineal gland.

Histamine (HA) is a potent stimulator of cAMP synthesis in various structures of chick brain, including the pineal gland. The action of HA is mediated by specific, membrane bound H(2)-like receptors, whose pharmacological profile is different from that described for H(2) receptors in mammalian tissues. In this work, we analyzed the effects of cholera toxin (CTX) and pertussis toxin (PTX), well-known modulators of G(s) and G(i)/G(o) protein, respectively, on the stimulatory action of HA on cAMP synthesis in the chick pineal gland organ cultures.

Suppression of melatonin biosynthesis in the chicken pineal gland by retinally perceived light - involvement of D1-dopamine receptors.

In this study the role of retinal dopamine (DA) receptors in the light-induced suppression of melatonin biosynthesis in the chicken pineal gland was examined. Exposure of dark-adapted chickens to low intensity light (4 lux) at night significantly decreased the activity of serotonin N-acetyltransferase (AA-NAT; the penultimate and key regulatory enzyme in melatonin production) and melatonin content in the pineal gland. This suppressive action of light was blocked by intraocular (i.

The relationship between melatonin and dopamine rhythms in the duck retina.

In the retina of duck, levels of dopamine (DA) and its main metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), fluctuate throughout the day, with high values during the light phase. The rhythmic changes in DA content and metabolism are out of phase with the daily oscillations in melatonin (MEL) and serotonin N-acetyltransferase (AA-NAT; the penultimate and key regulatory enzyme in MEL biosynthesis) activity. Acute exposure of ducks to light at night potently increased levels of DA and DOPAC, and decreased AA-NAT activity and MEL content in the retina.

Daily variation in the concentration of 5-methoxytryptophol and melatonin in the duck pineal gland and plasma.

The duck pineal gland rhythmically produces two 5-methoxyindole compounds, i.e. 5-methoxytryptophol and melatonin.