Multiple sites of action of the vitamin D endocrine system: FSH stimulation of testis 1,25-dihydroxyvitamin D3 receptors

Clinical Electrophysiology and Mathematical Modeling for Precision Diagnosis of Infertility

How can cellular electrophysiology measurements and mathematical modeling of ionic channels help to identify pivotal targets in disease-related cell signaling? The purpose of this review is to highlight the advantages and disadvantages of using both of these complementary techniques to determine molecular targets that may be structurally or functionally altered in a specific disease. In addition, both electrophysiology measurements and mathematical modeling may improve coordinated drug development, accelerate the prediction of new drugs, and facilitate repositioning of pharmacological agents. This review focuses on the data obtained from electrophysiology and mathematical model approaches, including intracellular recording, cellular patch clamp measurements, and the Hodgkin and Huxley equation, as key precision methodologies. To this end, seminiferous tubules, the Sertoli cell line (TM4), and/or primary cultures of Sertoli cells were used to explore the role of follicle-stimulating hormone (FSH), thyroid hormones, retinol, testosterone, and 1,25(OH)2 vitamin D3 in the coordinated activation or inhibition of ionic channels essential for male fertility. Based on the discussed data, Sertoli cells precisely regulate their biological activity by coordinating channel activity according to the hormonal environment and the nutritional requirements required for germ cell development.

Age-dependent effect of vitamin D supplementation on musculoskeletal health in chronic spinal cord injury patients: A pilot study

OBJECTIVE

To determine the effect of vitamin D supplementation on changes in body composition associated with musculoskeletal health status in patients with chronic SCI and vitamin D deficiency as a response to age.

DESIGN

Prospective drug-intervention study.

SETTING

Department of rehabilitation medicine, Veterans Health Service Medical Center.

PARTICIPANTS

Seventeen patients with vitamin D insufficiency/deficiency (<30 ng/mL) and chronic SCI were divided into two groups: groups A <65 years (n = 8) and B ≥65 years of age (n = 9).

INTERVENTIONS

Both groups received 800 IU/day cholecalciferol for 12 weeks.

OUTCOME MEASURES

We used blood samples to evaluate metabolites related to vitamin D, testosterone (T), lipid profiles, and sex hormone-binding globulin (SHBG). Bioelectrical impedance analysis (BIA) was used to evaluate body composition.

RESULTS

Group A had significantly better baseline clinical characteristics for all BIA measurements. SHGB was significantly higher in Group B (P = 0.003) and albumin was significantly higher in Group A (P = 0.000). When comparing pre- to post-treatment, Group A showed a significant improvement in T (P = 0.042), total cholesterol (P = 0.035), and triglyceride (P = 0.025) levels, whereas Group B significantly increased vitamin D (P = 0.038) and protein mass (PM) (P = 0.034) levels.

CONCLUSION

This study suggested that addressing vitamin D deficiency in patients with SCI had different effects in young and older adults, with both groups showing positive changes in body composition. Particularly, the increase in PM on BIA measurements in elderly patients at high risk of sarcopenia was encouraging.

Correlative studies on vitamin D and total, free bioavailable testosterone levels in young, healthy men

The relationship between vitamin D levels and testicular hormonal function in men has not been clearly established. Therefore, we aimed to investigate the relationship between deficiency/insufficiency levels of 25(OH)D and luteinizing hormone (LH), follicle-stimulating hormone (FSH), total (TT), free (FT), and bioavailable testosterone (BT), and sex hormone binding globulin (SHBG) in young, healthy men. We enrolled 176 healthy, active young men aged 18–35 years from a genetically homogenous population of Lower Silesia, Poland. Serum levels of 25(OH)D, LH, FSH, and TT were measured by electrochemiluminescence (ECLIA). FT levels were measured by enzyme-linked immunosorbent assay (ELISA). BT levels were calculated from TT, SHBG, and albumin. SHBG was measured by chemiluminescent immunoassay CLIA. We did not find any significant differences between the mean hormonal values (LH, FSH, TT, FT, BT, and SHBG) and the status of 25(OH)D level (deficient and insufficient). Based on our results, we concluded that there is no relationship between deficient and insufficient 25(OH)D concentration and androgen levels in young, healthy men.

Immunomodulatory Effects of Vitamin D in Pregnancy and Beyond

In addition to its role in calcium homeostasis and bone formation, a modulatory role of the active form of vitamin D on cells of the immune system, particularly T lymphocytes, has been described. The effects of vitamin D on the production and action of several cytokines has been intensively investigated in recent years. In this connection, deficiency of vitamin D has been associated with several autoimmune diseases, including rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), antiphospholipid syndrome (APS), Hashimoto Thyroiditis (HT), and multiple sclerosis (MS). In a successful pregnancy, the maternal immune response needs to adapt to accommodate the semiallogeneic fetus. Disturbances in maternal tolerance are implicated in infertility and pregnancy complications such as miscarriages (RM) and preeclampsia (PE). It is well-known that a subset of T lymphocytes, regulatory T cells (Tregs) exhibit potent suppressive activity, and have a crucial role in curtailing the destructive response of the immune system during pregnancy, and preventing autoimmune diseases. Interestingly, vitamin D deficiency is common in pregnant women, despite the widespread use of prenatal vitamins, and adverse pregnancy outcomes such as RM, PE, intrauterine growth restriction have been linked to hypovitaminosis D during pregnancy. Research has shown that autoimmune diseases have a significant prevalence within the female population, and women with autoimmune disorders are at higher risk for adverse pregnancy outcomes. Provocatively, dysregulation of T cells plays a crucial role in the pathogenesis of autoimmunity, and adverse pregnancy outcomes where these pathologies are also associated with vitamin D deficiency. This article reviews the immunomodulatory role of vitamin D in autoimmune diseases and pregnancy. In particular, we will describe the role of vitamin D from conception until delivery, including the health of the offspring. This review highlights an observational study where hypovitaminosis D was correlated with decreased fertility, increased disease activity, placental insufficiency, and preeclampsia in women with APS.

Vitamin D3 regulates apoptosis and proliferation in the testis of D-galactose-induced aged rat model

The age-associated imbalances between proliferation and apoptosis lead to impaired spermatogenesis and infertility. The age-associated decline in vitamin D3 levels has been reported and suggested the anti-aging potential of vitamin D3. However, the age-associated decline levels of vitamin D3 has not been studied in relation to the testicular activity. Thus, we investigated the effect of vitamin D3 on the expression of testicular proliferation markers, apoptotic markers, antioxidants system and oxidative stress in a D-gal-induced aged rat model. The present study investigated the levels of vitamin D3 and AGE in serum and testes along with the expression of the AGE-receptor (AGER) in the testis. Vitamin D3 treatment significantly increases cell proliferation and decreases apoptosis in a D-gal-induced aged rat testis. Furthermore, vitamin D3 significantly decreases oxidative stress in aged rat testis by improving the antioxidant defense systems. The expression of AGER was down-regulated by vitamin D3 treatment in aged testis. The circulating and intra-testicular AGE was higher in aged groups, however, only circulating vitamin D3 levels decreased in aged groups. The immunolocalization of VDR showed increased immunostaining in the testis by vitamin D3 treatment. Thus, it can be concluded that vitamin D3 delays testicular senescence by regulating proliferation and apoptosis.

Endocrine regulation of sperm release

Spermiation (sperm release) is the culmination of a spermatid’s journey in the seminiferous epithelium. After a long association with the Sertoli cell, spermatids have to finally ‘let go’ of the support from Sertoli cells in order to be transported to the epididymis. Spermiation is a multistep process characterised by removal of excess spermatid cytoplasm, recycling of junctional adhesion molecules by endocytosis, extensive cytoskeletal remodelling and final spermatid disengagement. Successful execution of all these events requires coordinated regulation by endocrine and paracrine factors. This review focuses on the endocrine regulation of spermiation. With the aim of delineating how hormones control the various aspects of spermiation, this review provides an analysis of recent advances in research on the hormonal control of molecules associated with the spermiation machinery. Because spermiation is one of the most sensitive phases of spermatogenesis to variations in hormone levels, understanding their molecular control is imperative to advance our knowledge of the nuances of spermatogenesis and male fertility.

Association of vitamin D intake and serum levels with fertility: results from the Lifestyle and Fertility Study

OBJECTIVE

To evaluate the role of vitamin D intake and serum levels on conception of clinical pregnancy and live birth.

DESIGN

Prospective cohort study.

SETTING

Academic medical centers.

PATIENT(S)

Healthy, nulliparous women, age 18-39 years, and their male partners.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy and live birth were compared between those who did or did not meet the vitamin D estimated average requirement (EAR) intake (10 μg/d) and with serum 25-hydroxyvitamin D (25(OH)D) considered at risk for inadequacy or deficiency (<50 nmol/L) or sufficient (≥50 nmol/L).

RESULT(S)

Among 132 women, 37.1% did not meet the vitamin D EAR and 13.9% had serum levels at risk for inadequacy or deficiency. Clinical pregnancies were significantly higher among women who met the vitamin D EAR (67.5% vs. 49.0%) and with sufficient serum 25(OH)D (64.3% vs. 38.9%) compared with those who did not. Live births were higher among those who met the vitamin D EAR (59.0% vs. 40.0%). The adjusted odds ratio (AOR) of conceiving a clinical pregnancy was significantly higher among those who met the EAR (AOR = 2.26; 95% confidence interval [CI], 1.05-4.86) and had sufficient serum 25(OH)D (AOR = 3.37; 95% CI, 1.06-10.70). The associations were not significant after controlling for selected nutrients and dietary quality.

CONCLUSION(S)

Women with vitamin D intake below EAR and serum 25(OH)D levels at risk for inadequacy or deficiency may be less likely to conceive and might benefit from increased vitamin D intake to achieve adequacy.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00642590.

Interactions between oestrogen and 1α,25(OH)2-vitamin D3 signalling and their roles in spermatogenesis and spermatozoa functions

Oestrogens and 1α,25(OH)₂-vitamin D₃ (1,25-D₃) are steroids that can provide effects by binding to their receptors localised in the cytoplasm and in the nucleus or the plasma membrane respectively inducing genomic and non-genomic effects. As confirmed notably by invalidation of the genes, coding for their receptors as tested with mice with in vivo and in vitro treatments, oestrogens and 1,25-D₃ are regulators of spermatogenesis. Moreover, some functions of ejaculated spermatozoa as viability, DNA integrity, motility, capacitation, acrosome reaction and fertilizing ability are targets for these hormones. The studies conducted on their mechanisms of action, even though not completely elicited, have allowed the demonstration of putative interactions between their signalling pathways that are worth examining more closely. The present review focuses on the elements regulated by oestrogens and 1,25-D₃ in the testis and spermatozoa as well as the interactions between the signalling pathways of both hormones.

Vitamin D supplement improved testicular function in diabetic rats

This study was designed to investigate the role that 1,25(OH)2D3 plays against testicular lesion in diabetic rats and try to find its possible mechanism of the steroidogenesis and the spermatogenesis. In diabetic rats, prolonged hyperglycemia evaluated inflammatory cytokines, damaged sperm production function and redox balance, diminished serum testosterone. After treated with 1,25(OH)2D3 at two different doses respectively for 12 months, all the alternations were effectively normalized. 1,25(OH)2D3 showed inhibitory effect on excessive inflammatory biomarkers and adjusted the expression reproductive genes and testicular androgen synthesis. It also upregulated Bcl-2 expression, decreased Bax and COX-2 expression and inhibited active caspase cascade (caspase 8 and caspase 3), which may preserved the testicular cells under diabetic condition. It revealed that vitamin D supplement may protect the cells through suppressing inflammation factors and alleviating cell apoptotic death, as well as upregulating the expression of genes related to reproductive and testosterone synthesis.

Relevance of vitamin D in reproduction

The steroid hormone vitamin D is historically recognized for its relevance to bone health and calcium homeostasis. Recent years have witnessed a shift in focus to non-skeletal benefits of vitamin D; in this latter context, an accruing body of literature attests to a relevance of vitamin D to reproductive physiology. This article reviews the existing data about the diverse and previously underappreciated roles for vitamin D in reproductive health. A large body of available literature suggests that vitamin D deficiency may be detrimental to reproductive biology. However, given that our appreciation of vitamin D's role in reproductive physiology is almost entirely shaped by 'associative' studies and that data based on prospective interventional trials are limited, these concepts remain predominantly conjectural. Exact mechanisms whereby vitamin D may participate in the regulation of reproductive physiology remain far from clear. This review underscores a need for appropriately designed intervention trials to address the existing knowledge gaps and to delineate the specific roles of vitamin D signaling in reproductive biology.

Vitamin D and fertility: a systematic review

BACKGROUND

Vitamin D has been well-known for its function in maintaining calcium and phosphorus homeostasis and promoting bone mineralization. There is some evidence that in addition to sex steroid hormones, the classic regulators of human reproduction, vitamin D also modulates reproductive processes in women and men.

AIM

The aim of this review was to assess the studies that evaluated the relationship between vitamin D and fertility in women and men as well as in animals.

METHODS

We performed a systematic literature search in Pubmed for relevant English language publications published until October 2011.

RESULTS AND DISCUSSION

The vitamin D receptor (VDR) and vitamin D metabolizing enzymes are found in reproductive tissues of women and men. Vdr knockout mice have significant gonadal insufficiency, decreased sperm count and motility, and histological abnormalities of testis, ovary and uterus. Moreover, we present evidence that vitamin D is involved in female reproduction including IVF outcome (clinical pregnancy rates) and polycystic ovary syndrome (PCOS). In PCOS women, low 25-hydroxyvitamin D (25(OH)D) levels are associated with obesity, metabolic, and endocrine disturbances and vitamin D supplementation might improve menstrual frequency and metabolic disturbances in those women. Moreover, vitamin D might influence steroidogenesis of sex hormones (estradiol and progesterone) in healthy women and high 25(OH)D levels might be associated with endometriosis. In men, vitamin D is positively associated with semen quality and androgen status. Moreover, vitamin D treatment might increase testosterone levels. Testiculopathic men show low CYP21R expression, low 25(OH)D levels, and osteoporosis despite normal testosterone levels.

1α,25(OH)2-Vitamin D3 stimulates rapid plasma membrane calcium influx via MAPK activation in immature rat Sertoli cells

It was characterized that the rapid response to 1α,25(OH)(2)-vitamin D(3) (1,25D(3)) on (45)Ca(2+) influx in rat Sertoli cells was mediated by voltage-dependent Ca(2+) channels (VDCCs), PKC, ERK1/2 and p38 MAPK pathways. In primary culture of 10 day-old rat Sertoli cells as well as in the whole testis, the time-course of (45)Ca(2+) influx did not change significantly in basal conditions. However, 1,25D(3) showed stimulatory effect on (45)Ca(2+) influx from 10(-15) to 10(-8) M after 60 s of incubation. The maximum effect was around 140% at 10(-12) M on purified Sertoli cells showing a steady state on (45)Ca(2+) influx between 10(-11) and 10(-9) M. Under this experimental condition, 1,25D(3) stimulated (45)Ca(2+) influx from 73% to 106% and no effect was observed at 10(-16), 10(-8) and 10(-7) M in whole testis. VDCC activities are mandatory for a full and complete stimulatory effect of 1,25D(3) in these approaches. K(+) and Cl(-) channels also are strongly involved in this rapid response coordinated by 1,25D(3). The participation of some selected kinases, points to PKC and ERK1/2 upstream activity to p38 MAPK activation suggesting an intracellular cross-talk between rapid (45)Ca(2+) influx and nuclear events. In addition, the comparative effect of microtubule disassembles and ClC-3 channel blocker on (45)Ca(2+) influx provides evidence of secretory activity of Sertoli cells triggered by 1,25D(3). Our results suggest that 1,25D(3) activates p38 MAPK and reorganizes microtubules, involving Ca(2+), PKC and ERK1/2 as upstream regulators and that extracellular Ca(2+) have a central role to rapidly start hormone-induced gene transcription and/or the secretory activity of Sertoli cell.

Regulation of aromatase expression by 1α,25(OH)2 vitamin D3 in rat testicular cells

It is well known that the vitamin D endocrine system is involved in physiological and biochemical events in numerous tissues, especially gut, bone and kidney but also testis. Therefore, in this study the effect and mechanisms of action of 1α,25(OH)2 vitamin D3 (1,25D) on aromatase gene expression in immature rat Sertoli cells were evaluated. Vitamin D receptor transcripts were present in immature Sertoli cells as well as in adult testicular germ cells and somatic cells. The treatment of immature Sertoli cells with 100 nM 1,25D increased the amount of aromatase transcript, mainly in 30-day-old rats. The protein kinase A (PKA) blocker, H89, partially inhibited the 1,25D effect. The stimulation of aromatase gene expression in 30-day-old Sertoli cells by the agonist 1α,25(OH)2 lumisterol3, and the suppression of the 1,25D effect by the antagonists 1β,25(OH)2 vitamin D3 and (23S)-25-dehydro-1α (OH)-vitamin D3-26,23-lactone suggested, besides a genomic effect of 1,25D, the existence of non-genomic activation of the membrane-bound vitamin D receptor involving the PKA pathway.

Role of 1alpha,25(OH)2 vitamin D3 on alpha-[1-(14)C]MeAIB accumulation in immature rat testis

1,25D3 is critical for the maintenance of normal reproduction since reduced fertility is observed in male rats on a vitamin D-deficient diet. Vitamin D-deficient male rats have incomplete spermatogenesis and degenerative testicular changes. In the present study we have examined the ionic involvement and intracellular messengers of the stimulatory effect of 1,25D3 on amino acid accumulation in immature rat testis. 1,25D3 stimulates amino acid accumulation from 10(-12) to 10(-6) M by increasing the slope to reach a maximum value at 10(-10) M, as compared to the control group. No effect was observed at a lower dose (10(-13) M). Time-course showed an increase on amino acid accumulation after 15, 30, and 60 min of incubation with 1,25D3 (10(-10) M). 1,25D3 stimulated amino acid accumulation in 11-day-old rat testis but not in testis that were 20 days old. Cycloheximide totally blocked the 1,25D3 action on amino acid accumulation. Furthermore, a localized elevation of cAMP increased the stimulatory effect of 1,25D3 and the blockage of PKA nullified the action of the hormone. In addition, 1,25D3 action on amino acid accumulation was also mediated by ionic pathways, since verapamil and apamine diminished the hormone effect. The stimulatory effect of 1,25D3 on amino acid accumulation is age-dependent and specific to this steroidal hormone since testosterone was not able to change amino acid accumulation in both ages studied. This study provides evidence for a dual effect for 1,25D3, pointing to a genomic effect that can be triggered by PKA, as well as to a rapid response involving Ca2+/K+ channels on the plasma membrane.

Testicular maturation arrest to testis cancer: spectrum of expression of the vitamin D receptor and vitamin D treatment in vitro

PURPOSE

We investigated the qualitative distribution of vitamin D receptor in human testis pathologies and performed an in vitro study of vitamin D receptor expression in a human testis cancer cell line model.

MATERIALS AND METHODS

Qualitative immunohistochemical analysis of vitamin D receptor in testis tumors, normal testis and specimens from infertile patients was performed. The human embryonal carcinoma cell line NT2/D1 (American Type Culture Collection, Manassas, Virginia) was cultured. Vitamin D receptor expression was examined by Western immunoblot analysis after incubating the cells with 250 to 800 nM vitamin D, 10 to 70 nM testosterone, 2 nM calcium or a combination of the 3 products.

RESULTS

Negative controls, synctiotrophoblasts and interstitial stroma did not stain positive for vitamin D receptor. Spermatogenic, Sertoli's, Leydig and tumor cells stained positive in all specimens. Embryonal carcinoma demonstrated more nuclear and cytoplasmic staining than other tumors. Vitamin D receptor expression was seen at 50 kDa in the cell line. Sequential concentrations of vitamin D increased vitamin D receptor expression intensity. Simultaneous addition of vitamin D and testosterone decreased the vitamin D receptor signal, as did testosterone alone. Delayed administration of vitamin D 5 hours after testosterone showed the return of vitamin D receptor expression. A combination of calcium, testosterone and vitamin D showed decreased or no vitamin D receptor expression. Calcium alone increased vitamin D receptor expression at later passages.

CONCLUSIONS

To our knowledge this is the first description of vitamin D receptor in different primary testis pathologies and in an embryonal carcinoma cell line. The in vitro model showed that vitamin D receptor is an active receptor and it is inducible with the addition of vitamin D. Testosterone may be important for vitamin D receptor down-regulation. Calcium may be an important co-factor in vitamin D receptor expression.

Vitamin D receptor found in human sperm

OBJECTIVES

Several animal studies have suggested that vitamin D and the vitamin D receptor (VDR) play a role in male fertility. The mechanism of action in the testis and the interaction with sperm is unknown. The presence of the VDR on sperm has never been demonstrated. The objective of this pilot study was to investigate the presence of the VDR on human sperm.

METHODS

A prospective study of sperm collected from 10 fertile men, mean age 33.7 +/- 2.2 years, was undertaken. Qualitative analysis for VDR was performed by immunohistochemistry using a monoclonal antibody to human VDR. For comparison of the spatial relationship of the receptor, qualitative analysis of the androgen receptor on sperm was performed. Immunoprecipitation and immunoblotting of total sperm protein lysate using VDR antibodies further characterized the VDR.

RESULTS

Immunohistochemistry demonstrated that the VDR was located predominantly on the head/nucleus of the sperm and mid-piece. Immunoblotting confirmed the presence of the VDR with a molecular weight of 50 kDa in all subjects.

CONCLUSIONS

Our results have demonstrated the presence of the VDR on human sperm for what we believe to be the first time.

Ligand structure-function relationships in the vitamin D endocrine system from the perspective of drug development (including cancer treatment)

It has become readily apparent to many scientists and pharmaceutical companies that the vitamin D endocrine system offers a wide array of drug development opportunities. There are already successes, as noted by 1alpha,25(OH)2D3 (Roche, and Abbott) for renal osteodystrophy and osteoporosis and 1alpha(OH)D3 (Leo, Chugai, Teijin) for renal osteodystrophy and (in Japan) osteoporosis, 1alpha,24(OH)2-24-cyclopropyl-D3 (Dovonex) and 1alpha,24(OH)2D3 (Teijin) for psoriasis, and 19-nor-1alpha,25(OH)2D2 (Abbott) for renal osteodystrophy, as well as drugs under active development. Yet there are still many important and challenging drug development frontiers, particularly in the area of cancer treatment and immune system disorders where exploration is only in the initial early stages. In addition, the application of vitamin D-related drugs in neurology and brain pathology should not be overlooked. It is to be hoped that the cellular and molecular basis for the vexing problem of analog-induced hypercalcemia will be elucidated. Given that there are believed to be over 2000 analogs of 1alpha,25(OH)2D3 already available for consideration, it is to be expected that over the next decade a significant number of new vitamin D structure-function drug development projects will be brought to conclusion.

Association of vitamin D receptors with the nuclear matrix of human and rat genitourinary tissues

Calcitrol, 1,25 dihydroxyvitamin D3 (1,25-D3) has an important role in the antiproliferative and growth regulatory effects on normal and neoplastic cells (e.g. prostate cancer cells). 1,25-D3 binds to the vitamin D receptor (VDR), a member of the steroid receptor superfamily. Steroids, via intranuclear receptors, have been demonstrated to have high affinity binding to the nuclear matrix, the tissue specific scaffolding of the nucleus that is involved in the organization of DNA, replication and transcription. We hypothesized that the VDR interacts closely with the nuclear matrix in both human and rat tissues. In the studies described here, nuclear matrix proteins (NMP) were extracted from a number of rat and human tissues and immunoblot analysis performed using a rat anti-VDR antibody. The results from these studies reveal that the anti-VDR antibody detects six forms of the VDR in the NMP preparations: human testis demonstrated a protein of 57 and 52 kDa molecular weight compared with 57 and 37 kDa in the rat testis. Human prostate demonstrated proteins of 52 kDa compared to rat ventral (57 and 37 kDa) and dorsal prostate (52 and 26 kDa). Human and rat bladder NMP demonstrated a protein binding at 55 kDa and rat seminal vesicle NMP binding at 48 kDa. This is the first report of VDRs associated with the nuclear matrix. The varying molecular weight proteins reactive with the anti-VDR antibody within these tissues may represent different isoforms, proteolytic cleavage of a larger VDR or post-translational modification. The VDR-NMP interaction may be involved in the tissue specific actions of 1,25-D3 especially growth regulatory and antiproliferative effects.

Homologous up-regulation of vitamin D receptors is tissue specific in the rat

1,25-dihydroxyvitamin D3 (1,25(OH)2D3) receptors (VDR) are expressed in multiple tissues within the body. VDR levels are increased by 1,25(OH)2D3 in intestine and kidney and in numerous cell models. The ability of 1,25(OH)2D3 to affect VDR levels in other target tissues in vivo was studied by assessing VDR levels by the 3H-1,25(OH)2D3 binding assay under varied physiological conditions in the rat. When compared with vitamin D-deficient (-D) controls, rats raised on a normal vitamin D-sufficient (+D) diet showed elevated VDR levels in kidney (391 +/- 53 vs. 913 +/- 76 fmol/g of tissue;p < 0.05), but not in testis, heart, or lung. Up-regulation of the VDR also occurred in kidney of +D rats 1 day after a single 100-ng dose of 1,25(OH)2D3 (454 +/- 43 vs. 746 +/- 113 fmol/mg of DNA; p < 0.05), but no changes were seen in intestine, testis, or lung. Because 1,25(OH)2D3-induced hypercalcemia may independently affect VDR regulation, 1,25(OH)2D3 was infused into -D rats, and normocalcemia was maintained by reduced dietary calcium intake. In this model, the renal VDR was again up-regulated (446 +/- 115 vs. 778 +/- 58 fmol/mg of DNA; p < 0.05), but VDR levels in testis and lung were unaffected. Scatchard analysis and tests of 1,25(OH)2D3 dose (1-100 ng/day for 7 days) and temporal (100 ng/day for 1-7 days) responsiveness further supported the tissue-specific nature of the homologous VDR regulation. Assay of VDR levels by L-1-tosylamido-2-phenylethyl chloromethyl ketone-3H-1,25(OH)2D3 exchange assay ruled out differences in endogenous 1,25(OH)2D3 occupancy as the basis for the observed differences in VDR regulation. Finally, coidentity of the VDR-like sites in kidney versus testis was confirmed by competitive binding analysis comparing their relative affinities for 25(OH)D3 versus 1,25(OH)2D3 (30.5 +/- 6.4 vs. 35.6 +/- 3.6 in kidney and testis, respectively) and by immunoblot analysis using a highly specific monoclonal anti-rat VDR antibody. Thus, under a wide variety of experimental conditions, homologous up-regulation of the VDR occurs in the rat kidney in vivo, but not in several other target tissues which do not regulate plasma calcium homeostasis. Moreover, this differential VDR regulation did not result from secondary changes in plasma calcium, from differential 1,25(OH)2D3 responsiveness in the various tissues, nor from differences in endogenous 1,25(OH)2D3 occupancy of the VDR. These studies thus establish that, in contrast to observations in vitro, the widely described phenomenon of homologous VDR up-regulation in kidney and intestine is not a universal property of 1,25(OH)2D3 target tissues in vivo in the rat.

Environmental temperature and cryptorchidism: effects on pregnenolone-sulfatase of mice testicular tissue

This study examined the capacity of abdominal organs, such as the scrotal testis, exposed to environmental temperature to hydrolyze pregnenolone sulfate. The cryptorchid state of exposure to 34 degrees C during 14 days decreased testis weight by 38 and 23%. But the enzymatic activity (nanomoles of free steroid/testis) was significantly higher (p < .05) compared with the control. Moreover, a rise in the environmental temperature combined with cryptorchidism in mice, two conditions that induced testicular damage, has been related to the elaboration of factors capable of modifying, through paracrine mechanism, the androgen biosynthesis. The presence of this factor could lead to an increase in the hydrolysis of pregnenolone sulfate, but as for cryptorchidism or high environmental temperature exposure, when cryptorchid mice were exposed to temperatures of 34 degrees C an apparent synergism of both conditions produced a decrease of 66% in testis weight. It would appear that the steroid sulfatase is predominantly located in the interstitial epithelium. This study suggests that cryptorchidism and hyperthermia damage the tubular epithelium by different mechanisms.

Immunohistochemical detection and distribution of the 1,25-dihydroxyvitamin D3 receptor in rat reproductive tissues

Vitamin D3, via its active metabolite 1,25-dihydroxyvitamin D3, plays a critical part in male and female reproduction in the rat. 1,25-Dihydroxyvitamin D3 activity is mediated by an intracellular receptor (VDR). VDR distribution in reproductive tissue has not been studied using antibodies against the receptor. We developed a polyclonal antibody against the VDR and used it to examine VDR distribution in male and female rat reproductive tissues. In rat testes, VDR epitopes were observed in seminiferous tubules, specifically in spermatogonia, Sertoli cells and spermatocytes. Spermatozoa stained faintly. Epithelial cells of the epididymis, seminal vesicles and prostate also expressed VDR epitopes. In the female rat reproductive tract, immunostaining for VDR was seen in ovarian follicles, specifically in granulosa cells. Weaker VDR immunostaining was observed in follicular thecal cells and in the ovarian stroma and germinal epithelium. Corpus luteal cells stained intensely for VDR. Epithelium of fallopian tubes and the uterus also contained VDR epitopes. Both nuclear and cytoplasmic VDR immunostaining was observed in male and female rat reproductive tissues. We conclude that the VDR is widely distributed in male and female reproductive tissues and that it is likely to mediate actions of 1,25-dihydroxyvitamin D3 in the tissues.

Vitamin D and prostate cancer

Our findings demonstrate the presence of VDR in various human prostate cancer cell lines and in primary cultures derived from normal, BPH and prostate cancer. In addition, 1,25-D induced several bioresponses in these cells including growth inhibition and PSA stimulation. Based on examples in many different malignant cells as well as our data in prostate cells, that vitamin D is anti-proliferative and promotes cellular maturation, it seem clear that vitamin D must be viewed as an important cellular modulator of growth and differentiation if addition to its classical role as regulator of calcium homeostasis. In this respect, vitamin D has the potential to have beneficial actions on various malignancies including prostate cancer. Its ultimate role in prostate cancer remains to be determined, but 1,25-D may prove useful in chemoprevention and/or differentiation therapy. We believe the data currently available provide the basis for an optimistic view on the possible use of vitamin D to treat prostate cancer in patients and that further investigation is clearly warranted to better define its potential therapeutic utility.

Absence of calbindin-D28 expression in nonclassical 1,25-dihydroxyvitamin D targets: analysis by polymerase chain reaction

CaBP-D28 mRNA expression in rat heart, testis, and lung was assessed by polymerase chain reaction (PCR). The animal model used was the hyperinduced vitamin D-treated rat (100 ng 1,25-dihydroxyvitamin D subcutaneously, daily for 7 days). For the PCR studies, two pairs of 20 mer oligonucleotide primers (designated 1-4 according to their position on the coding strand, but with primers 3 and 4 in reverse orientation) derived from the rat CaBP-D28 cDNA sequence were tested in various combinations. Optimal conditions were established using a 1:100 dilution of cDNA from normal rat kidney. Bands of the predicted sizes of 869 (1, 3), 994 (1, 4), 725 (2, 3), and 850 (2, 4) nucleotide base pairs resulted, but with varying intensities: 2,4 approximately 1,3 > 1,4 > 2,3. Repeat PCR (recycling after 1:100 dilution and readdition of reagents and primers with at least one different primer) provided strong additional amplification, particularly with the 1,4/2,4 combination. Under these conditions, mixing experiments showed that CaBP-D28 transcripts were detectable at 10(-7)- to 10(-9)-fold lower levels of expression than in D+ kidney. When RNA was isolated and cDNA generated from test tissues from 4 individual vitamin D-stimulated (D+) and vitamin D-deficient (D-) rats, repeat PCR (1,4/2,4 primer combination) provided no evidence of significant CaBP-D28 mRNA expression in the nonclassic target tissues, in contrast to strong bands in both the D- kidney (undiluted) and D+ kidney (1:100 dilution) preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiological effects of 1,25-dihydroxyvitamin D3 in TM4 Sertoli cell line

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] receptors have been previously described in Sertoli cells. This study was performed to assess biological activity of the receptor in the mouse Sertoli cell line TM4. A 2-h preincubation with 0.01-25 nM 1,25(OH)2D3 resulted in a dose-dependent rapid uptake of 45Ca2+ within 5 min of addition of the isotope to the cells (27 +/- 8%, n = 4 experiments; P less than 0.05). This response was specific for 1,25(OH)2D3, in that it was not induced by 25-hydroxyvitamin D3, estradiol, cortisol, R 5020 (promegestone), or testosterone. However, a combination of testosterone and 1,25(OH)2D3 inhibited uptake by 23 +/- 8% (n = 3 experiments, P less than 0.01). That the mechanism responsible for 1,25(OH)2D3-stimulated uptake may involve 1,25(OH)2D3 receptor interaction is supported by the observation that cycloheximide inhibited the response. Conversely, there was no detectable change in uptake by 1,25(OH)2D3-treated cells after 24-h incubation with 0.1-5 nM 1,25(OH)2D3. Increased levels of DNA and protein content also resulted from a 2-h incubation with the steroid and were sustained up to 24 h without a concomitant increase in cell number or a detectable change in cell morphology. The presence of specific 1,25(OH)2D3 receptor-like binding sites was demonstrated by sucrose gradient analysis and hydroxylapatite assay. These data demonstrate that 1,25(OH)2D3 may play an important role in testicular function through regulation of receptor-mediated events.

Light microscopic and ultrastructural pathology of seminiferous tubules of rats given multiple doses of Pasteurella multocida group D protein toxin

Male Holtzman rats were given subcutaneous doses of a purified Pasteurella multocida group D heat-labile toxin on alternate days for up to 22 days. Rats were necropsied at 18 days or 36 days (14 days after last dose of toxin) or when moribund, and testicles were taken for histologic and ultrastructural examination. Other selected tissues, including liver and spleen, were taken for histologic examination. Histologically, testicular and splenic lesions occurred more consistently and at much smaller doses when compared with lesions in other target organs such as liver. Testicular and splenic lesions were present in all rats (6/6) given 0.8 micrograms/kg toxin and were seen in some rats (1/6) given as little as 0.2 micrograms/kg toxin. Only 3/6 rats given 0.8 micrograms/kg toxin had hepatic lesions; no hepatic lesions were seen at doses of 0.2 micrograms/kg. Testicles from toxin-treated rats were smaller and weighed less than controls. Seminiferous tubules were moderately dilated and lined by polygonal sertoli cells. The normal spermatogenic maturation sequence and mature spermatids were absent, and many tubules contained multinucleate spermatocytes. Severely affected tubules were necrotic and mineralized. Ultrastructurally, there was necrosis of adluminal spermatocytes, multinucleate cell formation, and spaces between Sertoli cell plasma membranes. Testicular lesions were similar to those described for vitamin D-deficient rats, vitamin A-deficient rats, vasectomized rats, and rats given intravenous tumor necrosis factor; however, rats given lethal doses of toxin did not have elevated levels of TNF alpha activity.

Evidence for two classes of 1,25-dihydroxyvitamin D3 binding sites in classical vs. nonclassical target tissues

Possible differences in 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] binding sites in classical and nonclassical target tissues were tested by Scatchard analysis of [3H]1,25(OH)2D3 binding in parallel chromatin preparations of rat kidney vs. testis. Two distinct binding components were resolved in kidney (p less than 0.005). Moreover, the single binding site in testis exhibited a 10-fold lower Kd (p less than 0.05) than did the principal binding site in kidney (50 +/- 4 vs. 405 +/- 142 pM). Secondly, regulation of [3H]1,25(OH)2D3 binding sites also differed. 1,25(OH)2D3 injection resulted in increased 1,25(OH)2D3 binding (p less than 0.05) in kidney (92%) and intestine (415%), but not in testis, lung or heart. These results suggest that the principal 1,25(OH)2D3 binding sites in classical targets kidney and intestine may be intrinsically different from those in at least some nonclassical targets.

Vitamin D independence of small calcium-binding proteins in nonclassical target tissues

The presence and regulation of Ca-binding proteins (CaBPs) were investigated in newly identified 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] target tissues. 45Ca(2+)-blot analysis of proteins in normal rats yielded a 45Ca2+ band comigrating with authentic calmodulin. Additionally, a parvalbumin-like band (mol mass = 15.4 +/- 0.3 kDa) was prominent in prostate, and a strong unidentified 45Ca2+ band was always evident in the testis (mol mass = 23.5 +/- 0.7 kDa). Lung, bladder, and especially prostate demonstrated 45Ca2+ bands comigrating with the intestinal vitamin D-related CaBP (CaBP-D9K; mol mass = 10.9 +/- 0.5 kDa). Most tissues (including testis, heart, and lung) exhibited low levels of a 45Ca2+ band comigrating with the renal CaBP-D28K (mol mass = 28.3 +/- 0.4 kDa). Importantly, 45Ca2+ binding to all detectable CaBPs was unchanged in these four tissues in vitamin D-deficient rats, despite substantial downregulation of the intestinal CaBP-D9K and renal CaBP-D28K. Neither immunoblot analysis (rabbit anti-rat renal CaBP-D28K) nor Northern analysis (rat brain CaBP-D28K cDNA) provided evidence for coidentity of the 28-kDa 45Ca2+ band with the CaBP-D28K. Conversely, immunoblot analysis of lung, but not prostate, cytosol provided evidence for specific immunocross-reactivity to rabbit anti-rat intestinal CaBP-D9K. Immunoblot analysis of the 9-kDa CaBP in lung further confirmed its vitamin D independence. In conclusion, the vitamin D independence of the CaBPs in these putative new 1,25(OH)2D3 targets suggests the absence of an obligatory relationship between 1,25(OH)2D3 effects and CaBP induction therein.(ABSTRACT TRUNCATED AT 250 WORDS)