Simultaneous apocrine and merocrine secretion in the rat coagulating gland

Abstract

The coagulating gland of the rat synthesizes two prevalent secretory proteins (transglutaminase and 115 K) that are discharched in a different manner, one being secreted in an apocrine fashion (transglutaminase) and the other one in a merocrine way (115 K). Differences in the intra- cellular pathway and the release of either protein were studied using immunofluorescence on semithin sections, immunoelectron microscopy of preembedding-processed chopper sections and postembedding-processed ultrathin sections of rat coagulating gland. Immunohistochemical staining using an anti-transglutaminase antibody resulted in dense labeling of the cytoplasm of secretory cells and their apical blebs, whereas the cisternae of the rough endoplasmic reticulum and the Golgi apparatus were completely unlabeled. When, on the contrary, the anti-115 K antiserum was used, dense labeling of the cisternae of the rough endoplasmic reticulum, the Golgi apparatus, and the secretory granules was seen. Intraluminal secretion was also labeled, but the secretory blebs remained unlabeled. Our findings show that, in the coagulating gland of the male rat, the two secretory proteins studied are processed in parallel, but at completely different intracellular pathways. They are released via different extrusion mechanisms. Transglutaminase is synthesized outside the endoplasmic reticulum, reaches the apical cell pole by free flow in the cytoplasm, and is released via apocrine blebs, the membranes of which appear to be derived from the apical plasma membrane. The protein 115 K, on the other hand, follows the classic route, being synthesized within the cisternae of rough endoplasmic reticulum, subsequently glycosylated in the Golgi apparatus, and released in a merocrine fashion. The mutual exclusion of the two secretory pathways and the regulation of the alternative release mechanism are still unresolved issues.

Epididymosomes, prostasomes, and liposomes: their roles in mammalian male reproductive physiology

“…Although controversial, apocrine secretion is considered to be the major secretory pathway of the prostate. It seems that the reproductive tract extensively uses the apocrine secretion pathway, as R22 R Sullivan and F Saez it has been described in the prostate, seminal vesicles (Aumuller et al 1997), coagulating gland (Groos et al 1999), vas deferens (Manin et al 1995), epididymis (Hermo & Jacks 2002, Rejraji et al 2006, and, in females, in the uterus (Griffiths et al 2008).…”

“…The presence of these 20 nm diameter vesicles in the apical cytoplasm of cells forming blebs as well as in the intraluminal compartment suggests that they are liberated in the epididymal lumen once the blebs detach from the cells and disintegrate in the extracellular compartment. First described by Jones et al (1978) in boar andDavis (1980) in rabbit, they were thought to be an artifact due to poor tissue fixation (Aumuller et al 1999). Yanagimachi et al (1985) have nicely revisited the association of small membrane vesicles with epididymal spermatozoa in Chinese hamsters.…”

The coagulating gland in the male greater cane rat (Thryonomys swinderianus): morphological and immunohistochemical features

“…Glands that secrete by apocrine mechanism will normally have cells with apical blebs that contain secretory products and at different stages; some pinching off from the cell and discharged into the lumen and others still attached to the cells with few and scattered microvilli [32]. Although apocrine method of secretion have been described in the coagulating glands of most rodents [15,21,32] as well as in other glands in both animals and man [3,5,6,28], this secretion method always coexist with merocrine secretory activities in these glands [6]. The observations in the present study suggest apocrine secretory activities predominate in the coagulating gland of the cane rat.…”

“…Though absent in man, this gland in mice has also been reported to be embryologically homologous to the middle lobe and structurally related to the central zone of the human prostate [15,25]. It however, shows varying structural diversities that make it a distinct accessory sex gland especially among wild rodents [12,21] and which will possibly impact on its role in the reproduction of each of these wild species.…”

Apocrine secretion in accessory sex glands

“…Chez le taureau, les vesicules seminales secretent des exosomes qui se retrouvent dans le plasma seminal et qui s'apparentent donc aux prostasomes [1]. Chez le rat, la glande coagulante secrete des exosomes auxquels sont associees des activites transglutaminase et carbonyle anhydrase impliquees dans la formation du bouchon vaginal [5,28]. Le canal deferent chez la souris secrete egalement des exosomes montrant une activite aldose reductase qui est transferee aux spermatozoides mais dont la fonction demeure indeterminee [16,37].…”