RESUMO
The peptide hormone oxytocin has long been known to affect the life-span of the corpus luteum on administration. There is now a good deal of evidence to suggest that endogenous oxytocin may also be involved in this process, probably through a stimulatory action on uterine prostaglandin synthesis. Recently the role of oxytocin in controlling estrous cyclicity has been given added prominence by the discovery that oxytocin is secreted by the ruminant corpus luteum. This paper reviews current ideas in this area, and deals particularly with the mechanism of action of oxytocin.
Assuntos
Hormônios do Corpo Lúteo/farmacologia , Estro/efeitos dos fármacos , Ocitocina/farmacologia , Animais , Feminino , Gravidez , OvinosRESUMO
The ornithine decarboxylase (ODC) activity in cytosol and in dispersed cells of bovine corpora lutea was characterized in detail. The enzyme activity was maximal at an assay temperature of 38 C and was linear with respect to both duration of incubation and the amount of cytosol protein or cell number added. The pH optima for the enzyme was rather broad, i.e. 7.2 to 8.5. The apparent Km for ornithine (140-280 micro M) was similar for cytosol and cell ODC. Thiol compounds were required for the maximal enzyme activity and there was an absolute requirement for pyridoxal phosphate as a cofactor, with an apparent Km of 15 micro M. There was a modest competitive inhibition of ODC activity by the end products of ornithine catabolism. Human chorionic gonadotropin (hCG), prostaglandin (PG)E1, PGF2 alpha and cyclic nucleotides had no direct effect on ODC activity. There was no consistent response of ODC in cells and tissues slices pretreated with hCG and PGs. Only the corpus luteum part of bovine ovary of pregnancy contained ODC and this enzyme activity was unchanged throughout pregnancy.
Assuntos
Carboxiliases/metabolismo , Corpo Lúteo/enzimologia , Ornitina Descarboxilase/metabolismo , Animais , Bovinos , Gonadotropina Coriônica/farmacologia , Hormônios do Corpo Lúteo/farmacologia , Citosol/enzimologia , Ditiotreitol/farmacologia , Feminino , Técnicas In Vitro , Nucleotídeos Cíclicos/farmacologia , Ornitina/farmacologia , Gravidez , Prostaglandinas E/farmacologia , Prostaglandinas F/farmacologia , Fosfato de Piridoxal/farmacologiaRESUMO
A detailed review of the hormonal effects on intraocular pressure is presented. There is evidence that corticotropin, vasopressin, thyroxin, insulin, glucocorticoids and mineralocorticoids may play a role in the physiologic regulation of intraocular pressure. Growth hormone, melanocyte stimulating hormone, progesterone, estrogen, chorionic gonadotropin and relaxin may influence intraocular pressure when administered in pharmacologic doses. Whether the key to understanding primary open-angle glaucoma lies in recognizing abnormal endocrine mechanisms, especially involving glucocorticoids, remains unclear at the present time.
