Hormonal regulation of sulfated glycoprotein‐1 synthesis by nonciliated cells of the efferent ducts of adult rats

Abstract

The objective of this study was to define the factors regulating the endogenous production of sulfated glycoprotein-1 (SGP-1) in nonciliated cells of the efferent ducts. To this end we examined five different groups of animals undergoing the following experimental procedures: (1) hypophysectomized animals at 7, 14, and 28 days, (2) 7-day hypophysectomized rats receiving testosterone implants given at various time intervals thereafter, (3) castration at various time intervals up to 7 days, (4) 7-day castrated rats receiving testosterone implants at various time intervals thereafter, and (5) castrated rats given testosterone implants immediately after castration and sacrificed at different time intervals thereafter. Efferent ducts were fixed by perfusion with 4% paraformaldehyde and 0.5% glutaraldehyde in phosphate buffer for quantitative immunocytochemical analysis at the level of the electron microscope. For each experimental condition and their controls, the number of gold particles/micron2 within the endosomal and lysosomal compartments was calculated taking into account the changes in both the volume of the cell and organelles being quantified and expressed as labeling content. The results revealed that hypophysectomy (up to 4 weeks) caused a marked significant decrease in the SGP-1 labeling content of the endosomal and lysosomal compartments. The labeling content of the lysosomal compartment of efferent ducts from rats castrated for up to 1 week did not change significantly. However, there was a significant decrease in the labeling content of endosomes. This decrease is due to SGP-1, which is secreted by Sertoli cells, not being available for uptake in the efferent ducts. These results suggested that testosterone is not required for maintaining the high labeling content of SGP-1 within lysosomes of nonciliated cells, but that a pituitary factor appears to be needed. The administration of testosterone at different intervals to 7-day castrated animals resulted in a significant decrease of lysosomal SGP-1, suggesting that testosterone under these experimental conditions inhibits the production of a pituitary factor that maintains the high labeling content of SGP-1 within lysosomes of the nonciliated cells. Testosterone administered to 7-day hypophysectomized animals over a 24-hr period had no effect on the labeling content of SGP-1 within lysosomes. However, the administration of testosterone to animals immediately following castration showed no differences in the labeling content of SGP-1 within compared to controls.(ABSTRACT TRUNCATED AT 400 WORDS)

Regulation of Sulfated Glycoprotein‐1 and Cathepsin D Expression in Adult Rat Epididymis

“…In the efferent ducts, expression of SGP‐1 within lysosomes was not dependent on luminal or circulating androgens, nor was it dependent on a luminal factor entering the ducts from the testis (Rosenthal et al, 1995). However, the absence of SGP‐1 expression after hypophysectomy suggested that a pituitary factor, which may have a direct or indirect effect, is involved in its regulation in nonciliated cells of the efferent ducts (Rosenthal et al, 1995). Thus, different regulatory factors appear to come into play between the nonciliated cells of the efferent ducts and epithelial cells of the epididymis in the case of SGP‐1.…”

“…In a previous study we noted that SGP‐1 expression in the efferent ducts was not dependent on luminal or circulating testicular factors, but was regulated by a pituitary factor (Rosenthal et al, 1995). Thus, it is of interest to determine whether this is also true for SGP‐1 expression in the different cell types and regions of the epididymis.…”

Expression and tissue distribution of rat sulfated glycoprotein-1 (prosaposin).

“…In the reproductive system its expression appears to be induced by a pituitary factor (Rosenthal et al, 1995). Two mature forms of SGP-1 have been identified in Sertoli cells and in epithelial cells of the efferent ducts Igdoura et al, 1993): an intracellular form, which is also found in liver and spleen (O'Brien and Kishimoto, 1991).…”

Identification of a Novel Sequence Involved in Lysosomal Sorting of the Sphingolipid Activator Protein Prosaposin

“…The 70-kDa secretory prosaposin is a post-translationally modified form of the 65-kDa lysosomal prosaposin (27,28). This observation suggests that the Golgi apparatus must decode a sorting signal from the 65-kDa prosaposin to target it to the lysosomes before it is fully glycosylated in the distal compartment of this organelle.…”