Immunocytochemical localization of catechol estrogen in the rat pituitary gland. I Posterior lobe.

Abstract

Light and electron microscopic immunocytochemical observation of catechol estrogen localization in the posterior lobe of the rat pituitary gland was undertaken with a specific antibody to 2-hydroxyestrone coupled to bovine serum albumin and the peroxidase-antiperoxidase technique.Immunoreactive deposits were found in the pituicytes mainly in the peripheral part. The extended catechol estrogen-positive processes of the pituicytes enclosed or made contact with adjacent axon terminals and free extended catechol estrogen-positive processes were often found in the perivascular space. These results suggest that catechol estrogen may be involved in the regulation of neuroendocrine functions in the posterior lobe.Catechol estrogen is the major product of biotransformation of estrogen in man and rats. The possible significance of catechol estrogens as potential mediators of estrogen action and a direct biochemical link between estrogen and catecholaminergic function has been considered (1, 4, 12, 17-20, 27, 28, 32). Biochemical studies have shown that catechol estrogen is widely distributed in animal tissue including the pituitary gland (1,3,5,9, 12, 17, 21, 28,32,33). However, the physiological roles of catechol estrogen in the pituitary gland have not been determined, although they may be the links connecting primary estrogens and catechol amines in the regulation of gonadotropin and prolactin secretion (16, 30).We have already reported that the localization of catechol estrogen is shown by immunocytochemical methods in paraffin-embedded tissue (23). So in the hope that the cellular localization of catechol estrogen might give further clues to its function, the present study examined the distribution of catechol estrogen in the posterior lobe of the rat. MATERIALS AND METHODSImmunocytochemical procedures for light microscope observation. Eight adult Wistar rats (9-12 weeks old) of both sexes were anesthetized with Nembutal and perfused through the heart with 100 ml of periodate-lysine-paraformaldehyde (PLP) (29). After perfusion the posterior lobes were rapidly removed and fixed for three hr in PLP at 4°C, dehydrated through a graded series of alcohol and embedded in paraffin. Sections (5 ,czm) were cut, mounted on glass slides with egg albumin and glycerine and dried overnight at 37°C. For Immunocytochemical staining, paraffin sections were deparaffinized with xylene and brought to water through a graded series of alcohol. The sections were washed with distilled water and then treated with 0.005 M unbuffered periodic acid and 0.003 M unbuffered sodium borohydride to inhibit endogenous peroxidase (24) . They were subsequently incubated with a 1 : 50 dilution (in PBS) of normal goat serum for 30 min at room temperature. Sections were incubated for 24 hr at 4°C in a 1 : 1000 dilution (in PBS) of either rabbit antiserum (for details see references 23, 45) to 2-hydroxyestrone-l7-(0-carboxymethyl)-oxime bovine serum albumin (BSA) conjugate which was absorbed with BSA, or, as a control, in normal rabbit serum; then in a 1 : ...