Content of K+ and Na+in Seminiferous Tubule and Rete Testis Fluids from Sertoli Cell-enriched Testes1

Muffly, Karl E.; Turner, Terry T.; Brown, Melinda S.; Hall, Peter F.

doi:10.1095/biolreprod33.5.1245

Cited by 15 publications

(6 citation statements)

References 4 publications

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“…The existence of an isoform of the Na,K-ATPase with particular functional characteristics, such as a4, may be important in finely controlling Na þ and K þ electrochemical gradients to adjust cell ion content and membrane potential to the specific requirements of the different male germ cell types. The low affinity of a4 for extracellular K þ (lower than a1) (Blanco et al 1999) may correlate with the high K þ environment the male germ cells face once they migrate into the adluminal compartment of the seminiferous epithelium (Muffly et al 1985). Thus, at the high K þ concentration of the testis tubules, the cation does not affect a1, but can regulate a4 function, influencing the ion gradients across the plasma membrane, and the membrane potential of the cells.…”

Section: Discussionmentioning

confidence: 99%

Different expression and activity of the α1 and α4 isoforms of the Na,K-ATPase during rat male germ cell ontogeny

K¹,

Sánchez²,

An³

et al. 2005

Reproduction

105

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Two catalytic isoforms of the Na,K-ATPase, a1 and a4, are present in testis. While a1 is ubiquitously expressed in tissues, a4 predominates in male germ cells. Each isoform has distinct enzymatic properties and appears to play specific roles. To gain insight into the relevance of the Na,K-ATPase a isoforms in male germ cell biology, we have studied the expression and activity of a1 and a4 during spermatogenesis and epididymal maturation. This was explored in rat testes at different ages, in isolated spermatogenic cells and in spermatozoa from the caput and caudal regions of the epididymis. Our results show that a1 and a4 undergo differential regulation during development. Whereas a1 exhibits only modest changes, a4 increases with gamete differentiation. The most drastic changes for a4 take place in spermatocytes at the mRNA level, and with the transition of round spermatids into spermatozoa for expression and activity of the protein. No further changes are detected during transit of spermatozoa through the epididymis. In addition, the cellular distribution of a4 is modified with development, being diffusely expressed at the plasma membrane and intracellular compartments of immature cells, finally to localize to the midregion of the spermatozoon flagellum. In contrast, the a1 isoform is evenly present along the plasma membrane of the developing and mature gametes. In conclusion, the Na,K-ATPase a1 and a4 isoforms are functional in diploid, meiotic and haploid male germ cells, a4 being significantly upregulated during spermatogenesis. These results support the importance of a4 in male gamete differentiation and function.

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Section: Discussionmentioning

confidence: 99%

Different expression and activity of the α1 and α4 isoforms of the Na,K-ATPase during rat male germ cell ontogeny

K¹,

Sánchez²,

An³

et al. 2005

Reproduction

105

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“…Because myo-inositol is known to be important for osmoregulation in the kidney, we hypothesize that it may be performing the same function in the lumen as well. For example, the concentration of potassium is much higher in the luminal fluid as compared with the serum [1,3,28]. Because Sertoli cells, pachytene spermatocytes, and round spermatids are all expressing Isyna1 at an elevated level, it Ci of 3 H-myo-inositol.…”

Section: Discussionmentioning

confidence: 99%

Characterization of the Expression and Regulation of Genes Necessary for myo-Inositol Biosynthesis and Transport in the Seminiferous Epithelium1

Chauvin

Griswold

2004

Biology of Reproduction

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In many mammals, the concentration of myo-inositol in the fluid of the seminiferous tubules is dramatically higher than levels found in serum. Two enzymes involved in myo-inositol synthesis: myo-inositol-1-phosphate synthase (ISYNA1) and myo-inositol monophosphatase-1 (IMPA1), are known to have high activity in the testes. ISYNA1 is an isomerase that catalyzes the conversion of glucose-6-phoshate to myo-inositol-1-phosphate. IMPA1 then hydrolyzes the phosphate group to produce myo-inositol. Although no physiological role for the high concentration of myo-inositol has yet to be elucidated, it has been suggested that it could be involved in osmoregulation. Previous research on these enzymes in the testis has focused on enzyme activity. The objective of this study was to evaluate the expression of these genes and the myo-inositol transporter, Slc5a3, within the testis. Using Northern blot analyses, we found that all three genes, Impa1, Isyna1, and Slc5a3 are expressed in Sertoli cells. Isyna1 is highly expressed in two types of germ cells, pachytene spermatocytes and round spermatids. IMPA1 was expressed in round spermatids. Slc5a3 expression is upregulated when Sertoli cells are treated with 0.1 mM dibutyryl cAMP. When Sertoli cells were cultured in a hypertonic medium, there was an increase in the expression of Isyna1 and Slc5a3. We postulate that this upregulation is a result of the capability of the Sertoli cell to sense and then react to a change in osmolarity by increasing the transport and production of the osmolyte myo-inositol.

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“…If the primary defect lies within the germ cells per se abnormal transmembrane potentials could interfere with the extensive remodeling process. The Sertoli cell is responsible for the composition of the intratubular fluid [46, 47]; testis fluid has a lower K + /Na + ratio than is seen in other extracellular spaces, and presumably this milieu is necessary for normal sperm maturation. Additionally, cytosolic calcium levels are important for transduction of the FSH signal in Sertoli cells [48].…”

Section: Discussionmentioning

confidence: 99%

Hypothalamic-Pituitary-Gonadal Axis in the Mutant Weaver Mouse

Schwartz¹,

Szabó²,

Verina

et al. 1998

Neuroendocrinology

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The weaver (wv) mutant mouse manifests severe locomotor defects, a deficiency in granule cells of the cerebellum, and cellular deficits in the midbrain dopaminergic system. The wv phenotype is associated with a missense mutation in the pore region of the G-protein-gated inwardly rectifying potassium channel, GIRK2. The homozygous male wv mouse is essentially infertile due to an inadequate level of sperm production. Females are fertile although they also manifest the neurological phenotype. Homozygotes of both sexes have reduced body weight. We have evaluated the hypothalamic-pituitary-gonadal axis in heterozygote and homozygote male and female wv mutants in comparison with wild-type controls. Testicular weight was significantly reduced in the homozygous males, due to degenerative changes of seminiferous epithelium. Serum and pituitary content of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin were normal in all groups, and the normal sex differences were noted (FSH and LH higher in males, prolactin higher in females). Pituitary growth hormone (GH) concentration was normal, with control and mutant males showing higher GH than females. Serum testosterone levels were normal in the mutants, as was testicular testosterone. Testicular α-inhibin content was mildly reduced, but high in proportion to testicular weight. The defect in spermatogenesis appeared predominantly in the postmeiotic stages. In situ hybridization was consistent with expression of some GIRK2 mRNA isoforms in seminiferous epithelium. There were no significant differences between genotypes in the levels of dopamine, dihydroxyphenylacetic acid, serotonin and 5-hydroxyindoleacetic acid in the mediobasal and preoptic hypothalamic regions. Homovanillic acid levels in these two areas were, however, reduced in wv homozygotes compared to wild-type animals. In the light of normal pituitary hormone levels, normal hypothalamic monoamine concentrations and normal sex differences in gonadotropins, we conclude that the infertility in the male homozygote wv mouse lies within the tubule and is probably a primary defect in the germ cells. The hormonal data suggest that Leydig cell function, and at least some aspects of Sertoli cell function, are normal in the mutant mice.

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Content of K+ and Na+in Seminiferous Tubule and Rete Testis Fluids from Sertoli Cell-enriched Testes1

Cited by 15 publications

References 4 publications

Different expression and activity of the α1 and α4 isoforms of the Na,K-ATPase during rat male germ cell ontogeny

Different expression and activity of the α1 and α4 isoforms of the Na,K-ATPase during rat male germ cell ontogeny

Characterization of the Expression and Regulation of Genes Necessary for myo-Inositol Biosynthesis and Transport in the Seminiferous Epithelium1

Hypothalamic-Pituitary-Gonadal Axis in the Mutant Weaver Mouse

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