Ultrastructural Distribution of Calcium in the Rat Testis1

Abstract

Despite the important role of calcium in the growth and differentiation of a variety of cell types, its exact location and function in the somatic and germ cells of the testis remain to be determined. In the present study, we examined the subcellular distribution of calcium in the immature and adult rat testis. Calcium was localized at the electron microscopic level by ion-capture cytochemistry using combined oxalate and pyroantimonate procedures. Calcium-containing precipitates localized primarily within the nuclei, mitochondria, and cytosol of somatic and germ cells. Differences in the size and quantity of the calcium precipitates were observed among the various cellular compartments. In the somatic cells (Sertoli, Leydig, and myoid), the nuclei exhibited large round-shaped calcium-containing precipitates, whereas the mitochondria in these cell types contained numerous smaller precipitates. The cytoplasmic vesicles possessed single precipitates. These vesicles could be calciosomes, which have been described in other non-muscle cell types. Among germ cells, round spermatids exhibited a large number of vesicular, calsiosome-like structures in the cytoplasm containing single precipitates. The elongating spermatids from adult testis showed calcium localization within the nuclear matrix unassociated with the nuclear envelope, or in a peripheral alignment of precipitates along the nuclear envelope. Calciosome-like structures were also seen in round spermatids. Spermatogonia and spermatocytes exhibited calcium in nuclei, mitochondria, and cytoplasmic vesicles. These results demonstrate a differential distribution of calcium within the various cell types of the testis. The presence of calcium in the nucleus may suggest a role in cell growth and differentiation; calsiosome-like structures may represent the active exchangeable pool of calcium, and the differential type of distribution of calcium in elongating spermatids suggests a role for calcium in spermatid differentiation.

Localizations of intracellular calcium and Ca2+-ATPase in hamster spermatogenic cells and spermatozoa

“…This difference may be due to the different species used. In the hamster testis, the localizations of calcium precipitates in the cytoplasm and mitochondrial matrix in different spermatogenic cell types were similar to that described in a prior report (Ravindranath et al, 1994). During spermatogeneis, Sertoli and Leydig cells are under hormonal regulation by FSH and LH, respectively.…”

“…of all the cell types in the rat testis (Ravindranath et al, 1994), in sharp distinction to the current study conducted in hamster testis. This difference may be due to the different species used.…”

“…Ca 2þ and its ATPase play an important role in the process of cellular growth and differentiation, particularly as second messengers in signal transduction pathways in somatic cells (Ravindranath et al, 1994). A prior report suggested the presence of a large number of calcium containing precipitates within the nuclei Fig.…”

“…Sertoli cells, being secretory in nature, could be expected to possess calcium pools at the PM region for exocytosis of secretory products. FSH and calcium have been implicated in the process of exocytosis of proteins (Means et al, 1980;Ravindranath et al, 1994).…”

“…Very little is known about its involvement in the function of Sertoli, Leydig, and spermatogenic cells during spermatogenesis. Experimental studies have demonstrated that calcium is essential for the maintenance of cell shape, the regulation of protein secretion, estradiol biosynthesis, and transglutaminase activation in Sertoli cells Reichert, 1989, 1992;Means et al, 1980); Leydig cell steroidogenesis (Sullivan et al, 1986); and spermatid differentiation (Ravindranath et al, 1994). However, the role of calcium and its intracellular location in the different germ cell types has not been sufficiently characterized.…”