Metabolism of the TRH analog L-pyro-2-aminoadipyl-L-histidyl-[3H]-L-thiazolidine-4-carboxamide (MK-771) in gut and brain tissue of rats: the implications for its bioavailability.
Drug Metab Dispos
; 11(2): 147-51, 1983.
Article
en En
| MEDLINE
| ID: mdl-6133720
ABSTRACT
Hydrolysis of the terminal amide group of L-pyro-2-aminoadipyl-L-histidyl-[3H]-L-thiazolidine-4-carboxamide ([3H]MK-771) in rat brain homogenates was rapid and yielded the corresponding [3H] tripeptide carboxylic acid (III). Brain proteolytic enzymes may limit the bioavailability of [3H]MK-771. In contrast MK-771 degradation in a rat gut homogenate (where the radiolabeled product of hydrolysis was [3H]thioproline) was much slower and intestinal proteolytic enzymes probably did not prevent the absorption of MK-771 into the systemic circulation. However, the majority of an oral dose of MK-771 was not absorbed and intact MK-771 represented only 2% of the fecal radioactivity. Degradation of unabsorbed MK-771 occurred mainly in the large intestine of normal rats presumably because of the action of gut flora. Eighty percent of the oral dose remained in the intestine of germ-free rats as intact MK-771 and it was concluded that the limited absorption of MK-771 was caused by its inefficient transportation across gut membranes.
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Banco de datos:
MEDLINE
Asunto principal:
Encéfalo
/
Hormona Liberadora de Tirotropina
/
Sistema Digestivo
Límite:
Animals
Idioma:
En
Año:
1983
Tipo del documento:
Article