Influence of Catechol and Indole Amines upon Pineal Uptake of Thyroxine

Cady, P.; Dillman, Robert O.

doi:10.1159/000122009

Cited by 12 publications

(6 citation statements)

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“…Direct effects o f melatonin on pineal cells are suggested by the observation that the pineal gland exhibits the highest uptake of (3H)-melatonin 1 h after its intravenous administration to cats (Wurtman et al, 1964). Likewise incubation of bovine pineal slices with melatonin has been shown to enhance pineal thyroxine uptake, an effect not shared by its closely related compound serotonin (Cady and Dillman, 1971). The present report describes the occurrence o f melatonin-binding sites in membrane preparations from bovine pineal gland.…”

Section: Introductionmentioning

confidence: 52%

Binding Sites for Melatonin in Bovine Pineal Gland

Vacas¹,

Cardinali²

1980

Horm Res

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High-affinity binding of melatonin to crude membrane preparations of bovine pineal gland was examined by a rapid filtration procedure through Whatman GFB paper. Maximal melatonin binding was attained in 60 min at 37 °C, in 2 h at 25 °C and in 5 h at 0 °C; at 25 and 37 °C it was 36 and 42% of that at 0 °C. Specific binding was thermolabile and decreased following incubation with trypsin; it was also pH dependent, the maximum being observed at physiological pH. Melatonin binding was inhibited by the addition of monovalent or divalent ions to the incubation buffer. Subcellular fractionation studies indicated that 39 and 50% of binding was located in the pellets at 900 and 27,000 g whereas 11% was detected in the microsomal pellet. Scatchard analysis revealed a single population of binding sites with K_d= (7.0 ± 1.5) 10^-7M (mean ± SEM, n = 4); binding site concentration ranged from 185 to 356 fmol/mg of protein. When various melatonin analogues were tested for their ability to inhibit (³H)-melatonin binding, the following Ki values (10^-7M), were obtained: N-acetyl-serotonin 120, serotonin 130, 2-methyl indole 154, 5-hydroxytryptophol 218, 5-methoxytryptamine 266, 5-methoxytryptophol 660, tryptamine 1,740, 5-hydroxyindole acetic acid 3,455, 5-methoxyindole acetic acid 12,690, 5-hydroxytryptophan 13,600, and 6-hydroxymelatonin 55,550. These results suggest that melatonin receptors may be present in the pineal gland.

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Section: Introductionmentioning

confidence: 52%

Binding Sites for Melatonin in Bovine Pineal Gland

Vacas¹,

Cardinali²

1980

Horm Res

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“…In this context, Cady and Ddlmann [3] have shown that melatonin enhances the uptake of thyroxin by bovine pineal slices. Re cently we have presented results of a more elaborate study of the responses of pineal cells to melatonin microelectro phoresis [26], showing a pronounced circadian rhythm in the numers of excitatory and inhibitory effects.…”

Section: Discussionmentioning

confidence: 99%

Electrical Responses of Pineal Cells to Thyroid Hormones and Parathormone

Semm¹,

Demaine²,

Vollrath³

1981

Neuroendocrinology

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The effects of microelectrophoretic application of thyroxin, thyrocalcitonin and parathormone on pineal cells of urethane anesthetized guinea pigs were evaluated. A total of 162 cells were tested with thyroxin, 122 of these units also being subjected to the microelectrophoresis of the indolamine melatonin. 68 cells were excited by the administration of thyroxin, 63 were inhibited while the remaining cells did not respond. 79% of the cells tested with both thyroxin and melatonin responded in a similar way to the two substances. The responses to thyroxin varied significantly depending on whether the cells were tested during the day or at night. 104 pineal cells were tested with thyrocalcitonin, 20 U exhibiting an increased firing frequency, 58 showing an inhibitory response and the remaining 26 being unresponsive. Parathormone was applied to 64 pineal cells. Of the 43 cells responding to the hormone, 29 were excited and 14 showed decreased activity. In general, these results suggest that pineal cells may be subject to feedback control by the hormones of the thyroid and parathyroid glands.

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“…Several lines of evidence point to a local, intrapineal, role of melatonin. The pineal gland has a high capacity to take up melatonin from the bloodstream (22), and melatonin treatments alter several pineal morphological and biochemical parameters, including the number of dense-cored or granulated vesicles (23,24), thyroxine uptake (25), microtubular protein content (26), enzyme activity in melatonin pathway (26)(27)(28) and noradrenaline (NA) release and uptake (29). It was also early noted that melatonin injections alter 5-HT levels and block the rhythm in 5-HT content of the rat and ferret pineal gland (30,31).…”

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confidence: 99%

Evidence for a Regulatory Role of Melatonin on Serotonin Release and Uptake in the Pineal Gland

Míguez¹,

Simonneaux²,

Pévet³

1995

J Neuroendocrinology

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Melatonin has been proposed to exert some regulatory actions within the pineal gland itself. The present study examined the effect of melatonin on the release of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) from rat pineal glands by using an in vitro perifusion system. Melatonin induced a concentration-dependent stimulatory effect on 5-HT secretion from 10(-6) M to 10(-3) M. Maximal effects were obtained with melatonin 10(-3) M and concentrations lower than 10(-6) M were without effect. The secretion of 5-HIAA was inhibited by melatonin 10(-3) and 10(-4) M, but it was increased when pineals were incubated with 10(-5) and 10(-6) M of melatonin. The indoleamine secretion was also studied on peripherally denervated rat pineal glands. Basal output of 5-HT from these glands was increased when compared with those from control rats. In contrast, the secretion of 5-HIAA was strongly reduced after removal of the sympathetic input to the pineal gland. Melatonin 10(-3) M failed to stimulate 5-HT release from denervated pineal glands, although it inhibited 5-HIAA secretion. In contrast, melatonin 10(-5) M enhanced 5-HT release without altering 5-HIAA output. Fluoxetine, a 5-HT uptake inhibitor, produced similar effects than mM concentrations of melatonin on the indoleamine secretion from control pineal glands, but it had no effect on glands taken from peripherally denervated rats. These data suggest that mM concentrations of the pineal hormone are able to stimulate 5-HT release from the pinealocyte, while mM concentrations of melatonin increase extracellular 5-HT by inhibiting its reuptake in the adrenergic nerve endings. These findings are discussed in relation to the possible role of melatonin regulating the intra- and extracellular availability of 5-HT in the pineal gland and its significance as an autocrine factor.

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Influence of Catechol and Indole Amines upon Pineal Uptake of Thyroxine

Cited by 12 publications

References 0 publications

Binding Sites for Melatonin in Bovine Pineal Gland

Binding Sites for Melatonin in Bovine Pineal Gland

Electrical Responses of Pineal Cells to Thyroid Hormones and Parathormone

Evidence for a Regulatory Role of Melatonin on Serotonin Release and Uptake in the Pineal Gland

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