Summary
Day time rat pineal N-Acetyltransferase (P-NAT) activity is higher when homogenate used for incubation is diluted. Samples containing homogenate equivalent to 1/80 pineal gland had highest enzyme activity when compared with samples that contained homogenate equivalent to 1/40 and 1/20 pineal gland, respectively. Thus P-NAT activity is inhibited by a compound present in the pineal gland of the rat. This inhibition was not found in pineal glands of animals that had been injected with isoproterenol. Furthermore day time P-NAT activity is inhibited by excess of substrate, whereas even at 10 mmol/l of substrate isoproterenol stimulated P-NAT activity is not. It is suggested that these two phenomena are involved in the physiologic regulation of the circadian changes of P-NAT activity.
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References
Chan A, Ebadi M (1981) Evidence for existance of a serotonin N-Acetyltransferase inactivating substance in rat pineal gland. Endocr Res Commun 8: 205–227
Dubbels R, Schloot W (1981) Unterschiede in der Leber-N-Acetyltransferaseaktivität bei Laborratten nach Fütterung verschiedener Standarddiäten. Z Versuchstierk 23: 155–160
Eisenthal R, Cornish-Bowden A (1974) The direct linear plot. Biochem J 139: 715–720
Khoory R, Dubbels R, Schloot W (1985 a) A modified assay for rat pineal N-Acetyltransferase with enhanced sensitivity and indicating an inhibiting principle of the homogenate. In: Brown GM, Wainwright SD (eds) The pineal gland — endocrine aspects. Pergamon, Oxford, pp 53–58
Khoory R, Rommel B, Dubbels R, Schloot W (1985 b) N-Acetyltransferase of rat pineal gland acetylates isoniazid. Drug Res 35: 1821–1824
Klein DC, Auerbach DA, Namboodiri MAA, Wheler, GHT (1981) Indole metabolism in the mammalian pineal gland. In: Reiter RJ (ed) The pineal gland, vol 1: anatomy and biochemistry. CRC, Boca Raton, pp 199–228
Klein DC, Weller JL (1970) Indole metabolism in the pineal gland: A circadian rhythm in N-acetyltransferase. Science 169: 1093–1095
Namboodiri MAA, Favilla JT, Klein DC (1981) Pineal N-acetyltransferase is inactivated by disulfide-containing peptides: Insulin is the most potent. Science 213: 571–573
Namboodiri MAA, Weller JL, Klein DC (1980) Evidence of inactivation of pineal indoleamine N-acetyltransferase by protein thiol: disulfide exchange. J Biol Chem 255: 6032–6035
Rudeen PK, Reiter RJ, Vaughan MK (1975) Pineal serotonin-N-acetyltransferase activity in four mammalian species. Neurosci Lett 1: 225–229
Schloot W, Dubbels R, Birau N (1981) Genetics of melatonin. In: Birau N, Schloot W (eds) Melatonin — current status and perspectives. Pergamon, Oxford, pp 269–285
Snyder SH, Zweig M, Axelrod J, Fischer JE (1965) Control of the circadian rhythm in serotonin content of the rat pineal gland. Proc Soc Natl Acad Sci USA 53: 301–305
Voisin P, Namboodiri MAA, Klein DC (1984) Arylamine N-acetyltransferase and arylalkylamine N-acetyltransferase in the mammalian pineal gland. J Biol Chem 259: 10913–10918
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This study was supported by the Deutsche Forschungsgemeinschaft (Kh 8/1-1).
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Khoory, R., Schloot, W. Inhibition of day time, but not isoproterenol-stimulated pineal N-acetyltransferase activity by an unidentified pineal compound. J. Neural Transmission 66, 281–289 (1986). https://doi.org/10.1007/BF01260920
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DOI: https://doi.org/10.1007/BF01260920