Glucose‐6‐phosphatase activity of endoplasmic reticulum and Golgi apparatus in spermatocytes and spermatids of the rat: an electron microscopic cytochemical study

Abstract

Summary -The glucose-6-phosphatase (G6Pase) activity of cytoplasmic components of spermatocytes and spermatids of the rat was examined by electron microscope cytochemistry using cerium chloride as a capture agent. G6Pase activity, a recognized ERresident enzyme, was present in all ER cisternae of spermatocytes. In spermatids, while some ER cisternae were G6Pase-rcactive, others were negative or only slightly reactive, indicating an unequal distribution of the enzymatic activity throughout the network of ER cisternae in these cells. In spermatocytes, the c/s-and trans-elements of the stacks of Golgi saccules were slightly but significantly reactive for G6Pase. In the Golgi apparatus of spermatids, the c/s-element, 4 or 5 underlying saccules, as well as one or two thick trans Golgi elements were G6Pase reactive. The G6Pase activity of the various Golgi elements, fike that of the ER cisternae was not affected by the pH of the medium and was completely inhibited by Na-vanadate, a known G6Pase inhibitor. Sertoli and Leydig cells, submitted to the same cytochemical conditions, showed complete G6Pase reactivity of their ER; however in Sertoli cells, all Golgi components were consistently negative while in Leydig cells the c/s-and trans-elements of the Golgi stacks were slightly reactive, as in spermatocytes. Thus, the G6Pase reactivity of Golgi elements, appeared variable from one cell type to another. The compact juxtanuclear Golgi apparatuses of spermatocyte, and spermatids were both associated with numerous G6Pase reactive ER cisternae; some were present at their Curface, others crossed their cortices between Golgi stacks and formed elaborate networks in their cores. Other ER cisternae, in tur:,, were closely apposed to or intertwined with trans-elements of the Golgi stacks, a relationship raising the possibility of molecular ex~,,langes at this pole of the stacks in germinal cells.lllueose-6-phosphatme I endopluml¢ retleulum I Golgi apparatus I spermulocytes I spermatids

Organellar relationships in the Golgi region of the pancreatic beta cell line, HIT-T15, visualized by high resolution electron tomography

“…The first type of ER has a cisternal appearance, with ribosomes bound on only one surface; it flattens out to closely follow the cisternal membrane of C5. This first type resembles ER membranes that have been described by others in close association with the trans Golgi (6,(33)(34)(35)(36). The second kind of ER traverses the Golgi stack and is almost entirely devoid of bound ribosomes; its convoluted membranes form close contacts with C5, C6, and C7 in the heart of the trans Golgi region.…”

“…This ER corresponds to descriptions of smooth ER postulated to function in lipid metabolism at the trans Golgi face (37). Such sites of close apposition between the ER and trans Golgi have been proposed to facilitate molecular exchange between these two organelles (36,6), and may account for the trans-first scattering of Golgi enzymes after MT depolymerization (38).…”

Ultrastructural localization of enzymatic activity during spermiogenesis in two phytophagous bugs (Hemiptera: Pentatomidae)

“…Thiamine pyrophosphatase activity has been detected in the plasma membrane of insect (Baccetti, 1977;Báo & de Souza, 1994) and mollusc sperm cells , as well as in the Golgi complex and axoneme of some invertebrates (Yasuzumi & Lee, 1966;Báo & de Souza, 1994;Furtado & Báo, 1996). In addition, glucose-6-phosphatase activity has been shown in the endoplasmic reticulum and Golgi complex of rat (Thorne-Tjolmsland et al, 1991) and insects spermatids (Báo & de Souza, 1994;Furtado & Báo, 1996) and in the axoneme and mitochondrial compartments of spermatozoa of some invertebrate and vertebrate species (Anderson & Personne, 1970;Bigliardi et al, 1970). The existence of such enzymatic activity to cytochrome C oxidase in the mitochondrial derivatives has been previously described in insects (Anderson & Personne, 1970;Bigliardi et al, 1970;Baccetti et al, 1973;Báo et al, 1992).…”

Structure of the Golgi and Distribution of Reporter Molecules at 20°C Reveals the Complexity of the Exit Compartments

“…This ER, which displays ribosomes only where is it not adherent to Golgi cisternae, was described in multiple cell types during the 1960s and 1970s as part of the structure called "GERL" (Golgi, ER, lysosomal;Novikoff, 1964;Novikoff et al, 1971;Novikoff and Novikoff, 1977;Hand and Oliver, 1977). Later electron microscopy, using glucose-6-phosphatase reaction product to define the ER, showed clear association of ER with the trans-most cisterna in spermatids (Thorne-Tjomsland et al, 1991). In our current study the unique way in which the ER is associated with, and in some cases actually wrapped around, the bulging domains of the three trans-most cisternae strengthens the case that this is a structure/function relationship that is crucial to trans-Golgi processes.…”