[Identification of the existence of luteinizing hormone in pituitary vacuoles of rats].

ABSTRACT

It is generally believed that glycoprotein hormone exists in granules of the gonadotrophin (GTH) cells, and recent studies on the formation and secretion of glycoprotein hormones also concern much on the changes in the pituitary granules. In our previous studies, it was found that the secretion of luteinizing hormone (LH) was closely related to the morphological changes in pituitary vacuoles of rats, and the morphology of GTH cells was also closely related to the changes in vacuolar morphology. Therefore, it appears that there exists an inseparable relationship between the storage and secretion of LH and pituitary vacuoles. In order to examine whether the pituitary vacuoles contain LH in rats, and to further explore if LH is stored and released by the pituitary vacuoles, the vacuoles were separated and purified from pituitary, cortex and liver tissues by density gradient centrifugation. The vacuolar protein components, LH and glycoproteins were determined by the methods of SDS-PAGE, Western immunoblot and Con A/HRP, respectively. The results showed that (1) abundant protein components with various molecular masses were present in the vacuoles of the pituitary, cortex and liver in male, female and ovariectomized rats, and some of the protein components were similar in the molecular mass; (2) both pituitary tissues and vacuoles contained LH, and their LH levels had no significant difference by quantitative analysis of extracted protein samples; and (3) glycoproteins of various molecular masses were found in the vacuoles of the pituitary, cortex and liver, but the same position of stained glycoprotein band and LH molecular mass was only observed in the pituitary vacuoles. From the results given above, it can be concluded that LH specifically exists in the pituitary vacuoles, although there are some similar protein components in various cellular vacuoles. The possibility was further demonstrated at the molecular level that the pituitary vacuoles may have the function of storing and releasing LH due to the pituitary vacuoles containing LH with assembled glycone.