Effect of steroid hormones on Bufo arenarum oviduct. Ultrastructural study

Abstract

The endocrine regulation of the mucosa of the oviductal pars convoluta was analyzed by ultrastructural studies demonstrating that ovariectomy, together with a decrease in ovarian steroids circulating levels, caused a marked regression in this portion of Bufo arenarum oviduct. Twenty-five days after ovariectomy, a decrease in the depth of the epithelial and glandular layers was observed due to the notable loss of secretory cells, whose number was clearly smaller than in nonovariectomized females. The remaining secretory cells showed involution signs, with few secretory granules in their cytoplasm, little endoplasmic reticulum near poorly developed Golgi complexes and a large amount of lipid droplets. Cells in an advanced autolysis state were found in the lumen. These characteristics evidence a nonfunctional state of the pars convoluta. Treatment with 5alpha-dihydrotestosterone (DHT) completely reversed the ovariectomy effect, inducing pars convoluta growths and restoring the characteristics of epithelial and glandular secretory cells in the whole pars convoluta, with micrographs similar to the control. These same effects were observed after treatment with estradiol-17beta (E2), progesterone (P) o E(2)+P in the glandular layer of the whole pars convoluta, but only in the epithelial layer of the most anterior region of this duct. In the secretory cells of other segments these treatments induced the formation of granules of high electron density and homogeneous aspect. Each steroid had a particular effect on the pars convoluta. Although E2 and DHT induced the development of the organoids involved in the proteins biosynthesis, P and DHT acted as secretagogues.

Structural analysis of toad oviductal mucosa in relation to jelly components secretion throughout the reproductive cycle

“…Confirming our results, previous data obtained by TEM (Winik et al ., 1999) demonstrated that the secretion contains abundant material of heterogeneous aspect constituted by SG released from the GSC and flocculent material from the ESC and that, although exocytosis still prevails, we can often observe processes of apocrine and holocrine secretion (Winik et al ., 1999; Medina et al ., 2000; 2007). That is to say that in this species the release of the contents that will form the structure of the jelly coats includes several mechanisms that have not been demonstrated in other amphibians.…”

“…At present, data concerning the histological organization of the PC in relation to the process of secretion of the jelly components are scarce. It is known that the IPZ, only described and partially studied in Rhinella arenarum (Moreno, 1972; Winik et al ., 1999; Medina et al ., 2007) and Rhinella paracnemis (Alcaide & Cruz López, 2002), represents a zone of morphological, structural and functional transition. Morphologically, in this region, the oviduct is no longer straight and the first convolutions appear, represented by the first two handles of the PPC (Moreno, 1972).…”

Homeostasis and secretion of calcium in the oviductal mucosa of toad Rhinella arenarum

“…The apparition of the basolateral pump should take place during the postovulatory period, when the circulating concentrations of progesterone (P) are low, and androgens and estradiol (E 2 ) are high (Fernández et al, ; Medina et al, ), suggests that calcium pump is under estrogen regulation. Previous studies demonstrate that exogenous E 2 induces the development of the organoids that participate in the synthesis of numerous proteins, one of which could be the calcium pump (Fernández et al, ; Fernández and Ramos, ; Medina et al, ). Taken together, the present results demonstrate, for the first time in an amphibian that specific molecules participate both in the intracellular homeostasis of Ca 2+ and in the process of its secretion in the oviductal zone and thus implicated in the synthesis and secretion of jelly components.…”

“…In the toad Rhinella arenarum , as in other anuran amphibians, the oviducts are structurally and functionally divided into three main zones: the pars recta (PR), the pars convoluta (PC) and the ovisac or uterus (Moreno, ; Fernández et al, ; Winik et al, ; Medina et al, ). In these vertebrates, two types of oviductal secretion have been identified, each of them produced by a different portion of the duct and with a different biological role in fertilization.…”

Ultrastructure of the oviductal mucosa of Leptodactylus chaquensis. Analysis of the preovulatory and postovulatory periods

“…However, there are few studies that focus on the oviductal morphology of anurans and they are limited to some species and to some periods of the reproductive cycle (Shivers & James, 1970; Yoshizaki & Katagiri, 1981; Yoshizaki, 1985). Only the R. arenarum oviduct has been studied at the histological, ultrastructural and functional level throughout the reproductive cycle (Fernández et al , 1989; Winik et al , 1999; Fernández & Ramos, 2003; Medina et al , 2007; Crespo et al , 2009; Medina et al , 2012). With respect to L. chaquensis , at present the structural organization (Alcaide de Pucci, 1991b) and the histochemical analysis (Alcaide de Pucci, 1991a) of the oviduct during the preovulatory period have been studied by optical microscopy.…”