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Pinealectomy and pineal hormones modify cytochrome P450-dependent monooxygenase system in rat liver

100%

Plewka A., Kaminski M.

Polish Journal of Environmental Studies

1998

tom 07

nr 3

The cytochrome P450-dependent liver monooxygenase system is influenced by many endocrine glands. The components of the system show circadian rhythmicity and therefore their activities change during the day. This may suggest that the pineal gland, whose activity is strongly related to the external environment, influences this metabolic system. A growing interest in melatonin used as a nonprescription drug that inhibits aging and cures various diseases prompted us to investigate the influence of pineal hormones on the liver's metabolic system. The aim of this study was to evaluate the effect of pinealectomy, melatonin, or serotonin on the cytochrome P450-dependent monooxygenase system. The experiment was performed on sexually mature male Wistar rats. The rats were divided as follows: a control group, pinealectomized rats, melatonin-treated rats, and seroto- nin-treated rats. Pinealectomy was done 14 days before decapitation. The isolated microsomal fraction was assayed for the activity of cytochrome P450-dependent monooxygenase system and for the activity of the enzymatic system, which non-obligatorily cooperates with the MFO system. Both pinealectomy and prolonged administration of melatonin or serotonin modified the activity of the mixed function oxidase system. In all experimental groups the components of microsome electron-transport chain I were inhibited. In microsome electron-transport chain II only melatonin and serotonin produced an inhibitory effect, while pinealectomy did not affect cytochrome b5 and NADH-cytochrome b5 reductase. 4-Aminopyrine N-deme- thylase and aniline hydroxylase did not alter either after pinealectomy or melatonin treatment (only a decreasing tendency was noted). In contrast, serotonin treatment decreased these activities significantly.

Modulation of pancreatic enzyme secretion by melatonin and its precursor; L-tryptophan. Role of CCK and afferent nerves

80%

Leja-Szpak A., Jaworek J., Nawrot-Porabka K., Palonek M., Mitis-Musiol M., Dembinski A., Konturek S. J., Pawlik W. W.

Journal of Physiology and Pharmacology. Supplement

2004

tom 55

nr 2

33-46

Melatonin, a pineal hormone, is also produced in the gastrointestinal tract. Melatonin receptors have been detected in the stomach, intestine and pancreas. This indole inhibits insulin secretion but its role in the physiological modulation of exocrine pancreatic function is yet unknown. The aim of this study was to evaluate the pancreatic secretory effect of melatonin and its precursor; L-tryptophan given intraduodenally (i.d.) to the conscious rats with intact or capsaicin deactivated sensory nerves. CCK1 receptor antagonist; tarazepide, was used in the part of the study to determine the involvement of CCK in the secretory effects of melatonin. The secretory studies were performed on awaken rats surgically equipped with silicone catheters, one of them was inserted into pancreato-biliary duct, the other one - into duodenum. Melatonin (1, 5 or 25 mg/kg) or L-tryptophan (10, 50 or 250 mg/kg) were administered i.d. Samples of pancreatic juice were collected in 15 minutes aliquots. Tarazepide (2,5 mg/kg i.p.) was given to the rats 15 min prior to the administration of melatonin or L-tryptophan. Neurotoxic dose of capsaicin (100 mg/kg s.c.) was used to deactivate afferent nerves and thus to assess the role of these nerves in the melatonin-induced pancreatic enzyme secretion. Administration of melatonin (1, 5 or 25 mg/kg i.d.) or L-tryptophan (10, 50 or 250 mg/kg i.d.) significantly increased pancreatic amylase outputs. Deactivation of sensory nerves by capsaicin or administration of CCK1 - receptor antagonist; tarazepide, reversed the stimulatory effects of melatonin or L-tryptophan on pancreatic secretory function. Administration of melatonin or its amino-acid precursor to the rats resulted in the significant and dose-dependent rises of melatonin and CCK plasma levels. We conclude that melatonin or its precursor; L-tryptophan stimulates pancreatic enzyme secretion via stimulation of CCK release and activation of duodeno-pancreatic reflexes.

Effect of central administration of L-tryptophan [melatonin precursor] and luzindole [melatonin MT2 receptor antagonist] on the course of caerulein induced acute pancreatitis in the rat

80%

Nawrot K., Jaworek J., Bonior J., Leja-Szpak A., Kot M., Sendur R., Pawlik W. W., Konturek S. J.

Journal of Physiology and Pharmacology. Supplement

2001

tom 52

nr 2

Ograniczanie wyników

2 Journal of Physiology and Pharmacology. Supplement

1 Polish Journal of Environmental Studies

2 Jaworek J.

2 Konturek S. J.

2 Leja-Szpak A.

2 Pawlik W. W.

1 Bonior J.

1 Dembinski A.

1 Kaminski M.

1 Kot M.

1 Mitis-Musiol M.

1 Nawrot K.

1 Nawrot-Porabka K.

1 Palonek M.

1 Plewka A.

1 Sendur R.

1 2004

1 2001

1 1998

Wyniki wyszukiwania

Pinealectomy and pineal hormones modify cytochrome P450-dependent monooxygenase system in rat liver

Modulation of pancreatic enzyme secretion by melatonin and its precursor; L-tryptophan. Role of CCK and afferent nerves

Effect of central administration of L-tryptophan [melatonin precursor] and luzindole [melatonin MT2 receptor antagonist] on the course of caerulein induced acute pancreatitis in the rat