Effects of pinealectomy and melatonin treatment on liver and plasma metabolites in the goldfish, Carassius auratus

Delahunty, George; Bauer, G.; Prack, Margaret M.; Vlaming, Victor de

doi:10.1016/0016-6480(78)90151-x

Cited by 41 publications

(20 citation statements)

References 20 publications

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“…Most studies of rhythms of pituitary hormones such as prolactin and growth hormone were based on heterologous radioimmunoassays (Leatherland & McKeown 1973, Leatherland et al 1974, McKeown & Peter 1976, Spieler et al 1976, Delahunty et al 1978a), or histological studies (Leatherland & Nuti 1982). Because of this, the data must be interpreted with considerable caution, and additional studies, using homologous assay systems are required before rhythms in the plasma levels of these protein hormones can be validated.…”

Section: Die1 Rhythm Of Feedingmentioning

confidence: 99%

Circadian rhythms and feeding time in fishes

1992

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SynopsisAlthough several studies have described effects of meal frequency and timing of meals on growth performance and body composition of different species of fishes, the mechanisms by which such variables influence the energy partitioning processes is not known. They may interact with the natural feeding rhythm of the fish, or with various behavioural and physiological parameters that exhibit 'circadian-like' patterns; however, in most cases, the endogenous character of such rhythms is not clear. The time of feeding, perse, can act as a Zeitgeber and override the effect of the light/dark alternation. Fish that are fed always at the same time of day show typical pre-feeding activity. Blood levels of some nutrients and hormones also show peaks or troughs at the time of feeding, but whether these are pre-feeding or post-prandial events is not clear. These results from fish are compared with similar studies with mammals. The existence and location of an endogenous multi-oscillator system is also discussed.

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Section: Die1 Rhythm Of Feedingmentioning

confidence: 99%

Circadian rhythms and feeding time in fishes

1992

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“…Melatonin administration has been reported to increase [24][25][26][27] or decrease [27] or have no effects on blood glucose level [27,28]. The mechanism by which melatonin modulates plasma glucose is unknown.…”

Section: Introductionmentioning

confidence: 99%

Modulation of Blood Glucose by Melatonin: A Direct Action on Melatonin Receptors in Mouse Hepatocytes

Poon

Choy

Pang³

2001

Neurosignals

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Melatonin receptors were studied in isolated mouse hepatocytes using the 2[¹²⁵I]iodomelatonin binding assay. The binding of 2[¹²⁵I]iodomelatonin to hepatocytes isolated from the mouse using collagenase was stable, saturable, reversible and of high affinity. The equilibrium dissociation constant (K_d) obtained from saturation studies was 10.0 ± 0.4 pmol/l (n = 16), which was comparable to the K_d obtained from kinetics studies (6.9 ± 1.2 pmol/l, n = 3), and the maximum number of binding sites (B_max) was 2.9 ± 0.4 fmol/mg protein (n = 16). The relative order of potency of indoles in competing for 2[¹²⁵I]iodomelatonin binding was 2-iodomelatonin > 2-phenylmelatonin > 6-chloromelatonin > melatonin > 6-hydroxymelatonin > N-acetylserotonin, indicating that the binding was mediated by the ML₁ receptor subtype. The linear Rosenthal plots, the close proximity of the Hill coefficient to unity and the monophasic competition curves suggest that a single class of 2[¹²⁵I]iodomelatonin binding sites is present in the mouse hepatocytes. Guanosine 5′-O-(3-thiotriphosphate) dose-dependently inhibited 2[¹²⁵I]iodomelatonin by lowering the affinity of binding, while no inhibitory effects of adenosine nucleotides were observed, suggesting that the binding sites are G-protein linked. Western immunoblotting was used to identify the melatonin receptor subtype in mouse hepatocytes using anti-Mel_1a and anti-Mel_1b. Hepatocyte membrane extract reacted with anti-Mel_1b but not anti-Mel_1a giving a peptide-blockable band of 36 kD, supporting the hypothesis that the melatonin receptors in mouse hepatocytes are of the Mel_1b subtype. Melatonin injection and a high plasma glucose level affected 2[¹²⁵I]iodomelatonin binding in the whole mouse liver homogenates. Plasma glucose was elevated by mid-light intraperitoneal injection of melatonin (4 and 40 mg/kg body weight) in a dose-dependent manner with maximum elevation achieved 1 h after injection. 2[¹²⁵I]Iodomelatonin binding at this time showed increased K_d with no changes in B_max. When the plasma glucose returned to normal within 2 h, the binding remained lowered with increased K_d but no changes in B_max. Elevation of plasma glucose by 2-deoxyglucose injection (500 mg/kg), on the other hand, decreased the binding by decreasing the B_max without affecting the K_d. Suppression of plasma glucose by insulin injection (3 IU/kg) did not change the binding. Thus, melatonin may act directly on the liver to elevate the plasma glucose level, and changes in plasma glucose level itself may in turn affect hepatic melatonin binding.

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“…Melatonin, which is considered to be a chief hormonal product of the pineal gland, has a broad spectrum of physiological actions [3] which include thermoregulation [4,5], reproduction [1,6,7], intermediary metabolism [8], electrolyte metabolism [9], blood flow and evaporative water loss during heat stress in rats [10]. Melatonin is also implicated in immune response [11] and oncostatic action [12], Recent studies reveal that melatonin-induced release of opioid peptides mediate immunoenhancing effects [13], Ear lier studies from our laboratory indicated in volvement of melatonin in hemopoiesis and its rhythms [14].…”

Section: Introductionmentioning

confidence: 99%

Diurnal Sensitivity in Melatonin-lnduced Hematological Changes in the Male Albino Rat

Karimungi

Joshi²

1996

Neurosignals

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The influence of melatonin on diurnal changes in the hematological profile was investigated in male albino rats. Following treatment with melatonin, under two different experimental protocols, blood samples were collected at 06.00, 12.00, 18.00 and 24.00 h from separate groups of animals for detailed hematological analysis. In experiment 1, melatonin (25 µg, s.c.) treatment, once daily at 17.00 h for 4 weeks, led to an alteration in the rhythm of RBC production with a decrease in its counts at 12.00 h. The total WBC counts were increased at 06.00 and 12.00 h and decreased at 18.00 and 24.00 h. In experiment 2, twice-daily administration of melatonin (once at 09.00 h and again at 17.00 h), for 2 weeks, resulted in a decrease in total RBC counts at 06.00 and 24.00 h, whereas at 18.00 h there was an increase, compared to the respective control values. The total WBC counts increased at 06.00, 12.00 and 18.00 h and decreased at 24.00 h. Erythrocyte indices like mean cell volume (MCV), mean cell hemoglobin (MCH) and mean cell hemoglobin concentration (MCHC), in both experiments, correlated with RBC, hemoglobin and hematocrit values. The WBC differential counts in experiment 1 revealed a decrease in total neutrophils at 24.00 h, whereas in experiment 2 there was a general decrease in their number. While in experiment 1 the total lymphocyte number was increased at 06.00 h and decreased at 18.00 and 24.00 h, in experiment 2 it was increased except at 24.00 h. It may be concluded that melatonin has a modulatory role in hemopoiesis and its rhythms. The stimulatory effect of. melatonin on WBC supports its purported immunopotentiating action.

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Effects of pinealectomy and melatonin treatment on liver and plasma metabolites in the goldfish, Carassius auratus

Cited by 41 publications

References 20 publications

Circadian rhythms and feeding time in fishes

Circadian rhythms and feeding time in fishes

Modulation of Blood Glucose by Melatonin: A Direct Action on Melatonin Receptors in Mouse Hepatocytes

Diurnal Sensitivity in Melatonin-lnduced Hematological Changes in the Male Albino Rat

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