Endogenous steroid production in cellular and subcellular fractions of rat testis after prolonged treatment with gonadotropins.

Steroid production and enzyme activities were examined in preparations of whole testis tissue, isolated interstitial tissue and seminiferous tubules obtained from adult rats with intact pituitaries receiving daily subcutaneous injections of 100 I.U. human chorionic gonadotropin for 5 days and from control animals. After human chorionic gonadotropin administration testosterone concentrations were increased in total homogenates of whole testis tissue, interstitial tissue and seminiferous tubules. The testosterone production from endogenous precursors was enhanced only in total homogenates of whole testis tissue and interstitial tissue obtained from testes of human chorionic gonadotropin-treated rats. The production of testosterone in the corresponding homogenates of isolated seminiferous tubules was very low. The specific activity of 3 beta-hydroxysteroid dehydrogenase was increased in total homogenates of whole testis tissue, isolated interstitial tissue and seminiferous tubules. No effect was observed on the specific activities of marker enzymes such as cytochrome c oxidase, monoamine oxidase, steroid sulfatase and lactate dehydrogenase, whereas the specific activities of carboxyl esterase were decreased in homogenates of whole testis tissue and interstitial tissue. Total activity of monoamine oxidase was increased in homogenates of interstitial tissue of tests from human chorionic gonadotropin treated rats. After the same prolonged human chorionic gonadotropin treatment the concentration of pregnenolone was increased in mitochondrial fractions of whole testis tissue, interstitial tissue and seminiferous tubules, and the amount of protein isolated in the mitochondrial fraction of interstitial tissue increased by 40%. Steroid production (estimated as pregnenolone) from endogenous precusors by mitochondrial fractions of whole testis tissue and interstitial tissue were increased after human chorionic gonadotropin treatment, for whole testis from 580 pmol/mg mitochondrial protein per h to 1420 pmol/mg per h; and for interstitial tissue from 2665 pmol/mg per h to 7050 pmol/mg per h. The production of pregnenolone in mitochondrial fractions obtaine from isolated seminiferous tubules was very low and contributed hardly at all to the total pregnenolone production in mitochondrial fractions of whole testis tissue from normal rats as well as from human chorionic gonadotropin-treated rats.     

Relationship of the hormone-sensitive lipase-mediated modulation of cholesterol metabolism in individual compartments of the testis to serum pituitary hormone and testosterone concentrations in a seasonal breeder,the mink (Mustela vison)

The role of cholesterol differs in the two compartments of the testis. In the interstitial tissue, cholesterol is necessary for the synthesis of testosterone, whereas in the seminiferous tubules, membrane cholesterol content in developing germ cells will influence the gametes' fertility. Here we evaluate the hormone-sensitive lipase (HSL) modulation of the cholesterol metabolism in each compartment of the testis. Two HSL immunoreactive bands of 104- and 108-kDa were detected in Western blots performed with polyclonal anti-human HSL antibodies in the interstitial tissue (ITf)- and seminiferous tubule (STf)-enriched fractions generated from testes harvested at 30-day intervals during puberty and, in the adult mink, during the annual seasonal reproductive cycle. Epididymal spermatozoa expressed a 104-kDa HSL isoform, and HSL was active in these cells. Immunolabeling localized HSL to interstitial macrophages; Sertoli cells, where its distribution was stage specific; spermatids; and the equatorial segment of spermatozoa. Total HSL protein levels, specific enzymatic activity, and free cholesterol (FC):esterified cholesterol (EC) ratios varied concomitantly in STf and ITf and reached maximal values in the adult during the period of maximal spermatogenic activity. In STf, HSL-specific activity correlated with FC:EC ratios but not with triglyceride levels. In STf, high HSL-specific activity occurred concomitantly with high FSH serum levels. In ITf, HSL-specific activity was high during periods of low serum prolactin levels and high serum testosterone levels. The results suggest that 1) modulation of cholesterol metabolism in individual testicular compartments may be regulated by HSL isoforms expressed by distinct cells; 2) interstitial macrophages may be part of a system involved in the synthesis of steroid hormones and in the recycling of sterols in the interstitium, whereas in the tubules, recycling could be ensured by Sertoli cells; 3) there is distinctive substrate preference for testicular HSL; and 4) HSL may be the only cholesterol esterase in this location.     

Influence of experimental cryptorchidism on cholesterol side-chain cleavage enzyme and delta5-3beta-hydroxysteroid dehydrogenase activities in rat testes.

Testicular cholesterol side-chain cleavage enzyme (CSCCE) and delta5-3beta-hydroxysteroid dehydrogenase (delta5-3beta-HSD) activities were assessed 12 hours and 2, 4, 8, 16, and 32 days after surgical induction of bilateral cryptorchidism in adult rats. Within 12 hours after surgery CSCCE activity (expressed as dpm of isocaproic acid-14C formed from cholesterol-26-14C/3 hours/testis) was significantly reduced (P less than 0.01) in cryptorchid testes to approximately 55% of sham-operated control values and remained depressed at less than 50% of control activities 2, 4, 16, and 32 days after surgery. Cryptorchid testis delta5-3beta-HSD activity (measured by a pregnenolone substrate-depletion assay and expressed as mumoles of products/30 minutes/testis) did not differ from controls (P greater than 0.05) 1/2, 2, or 4 days after translocation of testes to the abdominal cavity. By day 8 of cryptorchidism, however, delta5-3beta-HSD activity was reduced to 60% of control values (P less than 0.05) and continued to decline to approximately 30% of controls during the remainder of the experimental period. These observed alterations in enzyme activities suggest an impairment in the ability of cryptorchid rat testes to synthesize androgens and further indicate that testicular CSCCE is more acutely sensitive to the cryptorchid milieu than delta5-3beta-HSD.     

Steroid sulfatase activity in homogenates, microsomes and purified Leydig cells from adult rat testis

Steroid sulfatase (STS) activity was studied in the Long-Evans rat testis. The rate of dehydroepiandrosterone sulfate (DHA-S) hydrolysis determined in whole testis homogenates was low compared to that of the corresponding microsomal fractions, which was, in contrast, as high as that expressed in homogenates from purified Leydig cells. Such an increment in STS activity between total homogenates and the corresponding microsomes was not observed for the seminiferous tubules. The STS affinity reported for total testicular microsomes (Km = 3.47 +/- 0.54 microM; mean +/- SEM) was of the same magnitude as that previously reported for Leydig cells, but was about 3 times higher than that measured for whole testis homogenate (Km = 10.11 +/- 0.92 microM). In vivo hCG treatment decreased the STS affinity in total testicular microsomes without affecting this kinetic parameter in whole testis homogenate. These data suggest that the steroid sulfatase expressed in total testicular microsomes (activity and regulation by hCG) could be considered as a good index of Leydig cell STS activity.     

Intercellular transport of steroids in the infused rabbit testis

Tritiated-pregnenolone and tritiated-testosterone were infused via the testicular artery into the rabbit testis in situ, in order to determine if steroids can pass the "blood-testis barrier". After various periods of infusion (5-60 minutes) the testis were frozen cryostat sections were cut and freeze-dried. Interstitium and tubules were isolated by micro dissection and radioactivity per mcg dry weight was measured in both tissue compartments. Radioactive steroids could be isolated from the interstitial tissue as well as from the seminiferous tubules. Levels of radioactivity in the testes after infusion of tritiated-pregnenolone varied from 4 to 50% of the infused dose and were found to be dependent on the type of perfusion medium and the duration of the perfusion. Separation and identification of the radioactive steroids after infusing tritiated prognenolone showed that pregnenolone and testosterone were the major radioactive steroids in both interstitium and seminiferous tubules. After infusion with tritiated-testosterone, both tritiated-testosterone (77%) and tritiated-androstenedione (23%) were dound in the seminiferous tubules. It is concluded that steroids can be transported from the Leydig cells to the seminiferous tubules.     

Comparison of components of the testis interstitium with testosterone secretion in hamster, rat, and guinea pig testes perfused in vitro

Components of the testis and cytoplasmic organelles in Leydig cells were quantified with morphometric techniques in hamster, rat, and guinea pig. Testosterone secretory capacity per gram of testis and per Leydig cell in response to luteinizing hormone (LH) (100 ng/ml) stimulation was determined in these three species from testes perfused in vitro. Numerous correlations were measured among structures, and between structures and testosterone secretion, to provide structural evidence of intratesticular control of Leydig cell function. Testosterone secretion per gm testis and per Leydig cell was significantly different in the three species: highest in the guinea pig, intermediate in the rat, and lowest in the hamster. The volume of seminiferous tubules per gm testis was negatively correlated, and the volumes of interstitium, Leydig cells, and lymphatic space per gm testis were positively correlated with testosterone secretion. No correlations were observed between volumes of blood vessels, elongated spindleshaped cells, or macrophages per gm testes and testosterone secretion. The average volume of a Leydig cell and the volume and surface area of smooth endoplasmic reticulum (SER) and peroxisomes per Leydig cell were positively correlated, and the volume of lysosomes and surface area of inner mitochondrial membrane per Leydig cell were negatively correlated with testosterone secretion. No correlations were observed between volume and surface area of rough endoplasmic reticulum (RER), Golgi apparatus, and lipid, and volume of ribosomes, cytoplasmic matrix, and the nucleus with testosterone secretion per Leydig cell. These results suggest that Leydig cell size is more important than number of Leydig cells in explaining the difference in testosterone-secreting capacity among the three species, and that this increase in average volume of a Leydig cell is associated specifically with increased volume and surface area of SER and peroxisomes. An important unresolved question is what is the role of peroxisomes in Leydig cell steroidogenesis.     

On the regulation of rat testicular steroidogenesis. Short term effect of luteinizing hormone and cycloheximide in vivo and Ca2+ in vitro on steroid production in cell-free systems.

An attempt has been made to correlate the rapid effect of luteinizing hormone on testicular steroid production in vivo with testicular steroid concentrations and in vitro steroid production rates in testis tissue preparations. Within 20 min after intravenous administration of 25 mug luteinizing hormone, increases were observed in testosterone concentrations in testicular venous plasma and in whole testis tissue and in pregnenlone concentrations isolated testis mitochondrial fractions. Testosterone production by whole testis homogenates and pregnenolone production by isolated mitochondrial fractions were significantly increased within 5 min after in vivo administration of luteinizing hormone. Injection of cycloheximide 10 min prior to luteinizing hormone prevented the stimulating effect of luteinizing hormone to steroid levels in testicular venous plasma and testis tissue and on steroid production rates by preparations of rat testis tissue. Cycloheximide treatment of control animals did not significantly alter testosterone concentrations and testosterone production rates vitro, although mitochondrial pregnenolone concentrations and production rates were decreased. Testosterone production by whole testis homogenates as well as the pregnenolone production by isolated mitochondrial fractions obtained from luteinizing hormone treated testes and control glands showed a biphasic time curve A period (5-10 min) of high steroid production was followed by a period lower steroid production. Addition of 25 mug luteinizing hormone or 10(-8)--10(-5) M adenosine 3':5'-monophosphate (cyclic AMP) to the incubation medium had no effect pregnenolone production by isolated mitochondrial fractions. Administration of leuteinizing hormone in vivo markedly enhance the stimulating effect of Ca2+ on testosterone production by whole testis homogenates and on pregnenolone production by isolated mitochondrial fractions.     

Morphometric studies on hamster testes in gonadally active and inactive states: light microscope findings

This study provides quantitative information on the testes of seasonally breeding golden hamsters during active and regressed states of gonadal activity. Seminiferous tubules occupied 92.5% of testis volume in adult gonadally active animals. Leydig cells constituted 1.4% of the testicular volume. The mean volume of an individual Leydig cell was 1092 microns 3, and each testis contained about 25.4 million Leydig cells. The volume of an average Sertoli cell nucleus during stage VII-VIII of the cycle was 502 microns 3. A gram of hamster testis during the active state of gonadal activity contained 44.5 million Sertoli cells, and the entire testis contained approximately 73.8 million Sertoli cells. Testes of the hamsters exposed to short photoperiods for 12-13 wk displayed a 90% reduction in testis volume that was associated with a decrease in the volume of seminiferous tubules (90.8% reduction), tubular lumena (98.8%), interstitium (72.7%), Leydig cell compartment (79.3%), individual Leydig cells (69.7%), Leydig cell nuclei (50.0%), blood vessels (85.5%), macrophages (68.9%), and Sertoli cell nuclei (34.1%). The diameter (61.1%) and the length (36.8%) of the seminiferous tubules were also decreased. Although the number of Leydig cells per testis was significantly lower (p less than 0.02) after short-photoperiod exposure, the number of Sertoli cells per testis remained unchanged. The individual Sertoli cell in gonadally active hamsters accommodated, on the average, 2.27 pre-leptotene spermatocytes, 2.46 pachytene spermatocytes, and 8.17 round spermatids; the corresponding numbers in the regressed testes were 0.96, 0.20, and 0.04, respectively. The striking differences in the testicular structure between the active and regressed states of gonadal activity follow photoperiod-induced changes in endocrine function and suggest that the golden hamster may be used as a model to study structure-function relationships in the testis.     

Impact of fine needle aspiration (FNA) and of the number of punctures on the feline testis: clinical, gross anatomy and histological assessment

The safety of testicular fine needle aspiration (FNA) has been proven in dogs but has not been fully established in men, while studies in rats have given contradictory results. Furthermore, the extent of damage inflicted by multiple punctures is unknown. The aim of this study was to determine the impact of FNA and of the number of punctures on the feline testis with clinical, gross anatomy and histological examinations. Twenty-seven sexually mature healthy laboratory Domestic Shorthair cats were randomly assigned to two groups: 5 cats in which no FNA was performed (control group), and 22 cats which had their left and right testis punctured with a 26 ga needle towards 3 and 8 directions, respectively (experimental group). Two cats at a time were orchiectomized 5 or 30 min, 1, 2, 4, 7 or 14 days or 1, 2, 3 or 4 mo post-aspiration. The cats of the control group were also orchiectomized. During the first week post-aspiration clinical examination revealed vaginal cavity hematoma (8/44 testes), while the histological findings were focal hemorrhagic areas (20/24 testes), erythrocytes inside the seminiferous tubules' lumen (9/24 testes), and germinal cell degeneration in <1.94% of the seminiferous tubules (15/24 testes). After the first week the histological findings were germinal cell degeneration in <2.14% of the seminiferous tubules (19/20 testes) and enlargement of the lumen of <5.16% of the seminiferous tubules (7/20 testes). The germinal epithelium and interstitium had an overall normal appearance. No significant differences were observed between the left and right testis. The results of the study indicate that testicular FNA should be considered a safe procedure in the cat when up to 8 punctures are performed.     

Stage dependent and androgen inductive expression of orphan receptor TR4 in rat testis

In this study, we investigated the expression of TR4 in different stages of seminiferous tubules and the relationship between TR4 and androgen in rat testis. We found that TR4 was stage-dependently expressed in rat seminiferous tubules, T withdrawal induced by high doses of testosterone undecanoate and ethane dimethane sulfonate inhibit TR4 expression in rat testis, and testosterone induced TR4 expression in co-cultured primary germ/Sertoli cells. Furthermore, we demonstrated that androgen receptor could enhance TR4-mediated transactivation activity in testis cells in the presence of testosterone. Together, these data indicate that the expression of TR4 in rat testis is stage dependent and androgen inductive, and suggest the important role of orphan receptor TR4 in spermatogenesis.     

Expression, activity, and subcellular localization of testicular hormone-sensitive lipase during postnatal development in the guinea pig

The present work reports on testicular hormone-sensitive lipase (HSL), the biological significance of which has been documented in male fertility. The HSL protein levels and enzymatic activity were measured, respectively, by densitometry of immunoreactive bands in Western blots, performed with antibodies against recombinant rat HSL, and by spectrophotometry in seminiferous tubules (STf) and interstitial tissue (ITf) enriched fractions generated from neonatal, pubertal, and adult guinea pig testes. In addition, HSL was studied in subcellular fractions obtained from STf isolated from adult testes and in epididymal spermatozoa (Spz). A 104-kDa HSL protein was detected in STf and ITf, the expression and activity of which increased with testicular development. Three immunoreactive bands of 104, 110, and 120 kDa were detected in the lysosomal subfraction, and two bands of 104 and 120 kDa were detected in Spz. The HSL activity was positively correlated with free (FC) and esterified (EC) cholesterol ratios in STf and ITf, but not with triglyceride (TG) levels, during testicular development. Immunolabeling localized HSL to elongated spermatids and Sertoli cells, where its distribution was stage-dependent, and within the cells lining the excurrent ducts of the testis. The findings of the 104- and 120-kDa HSL immunoreactive bands and of HSL activity in Spz as well, as the detection of the 104-, 110-, and 120-kDa immunoreactive bands in lysosomes, suggest that part of HSL may originate from germ cells and be imported in Sertoli cells. The HSL protein levels and enzymatic activity in ITf and STf were positively correlated with serum testosterone levels during development. To the best of our knowledge, this study is the first to contribute insights regarding the impact of HSL on FC:EC cholesterol ratios and TG levels in the interstitial tissue and tubules in relation to serum testosterone levels during postnatal development, and regarding the immunolocalization of the enzyme in regions of the male gamete consistent with spermatozoa-oocyte interaction.     

Ontogenesis and regulation of steroid sulfatase activity in Leydig cells and seminiferous tubules in the Long-Evans rat

Steroid sulfatase (STS) activity was studied in Long-Evans rat testis. The affinity of the enzyme was shown to increase during postnatal development and to be always higher in purified Leydig cells than in seminiferous tubules. STS activity appeared to be higher in the seminiferous tubules at the earlier stages. In vivo injection of 100 IU hCG resulted in a decrease in the affinity and an increase in the activity of the enzyme expressed in Leydig cells with no such modification in seminiferous tubules. This suggests that STS could play a regulatory role in testosterone production by Leydig cells.     

Differential metabolism of pregnenolone by testicular homogenates of humans and two species of macaques. Lack of synthesis of the human sex pheromone precursor 5,16-androstadien-3 beta-ol in nonhuman primates.

In previous reports we described the early time sequence in in vitro [4-14C] pregnenolone metabolism in human and rat testicular homogenates and, apart from a difference in the preferred route of the conversion of pregnenolone to testosterone, we demonstrated the presence of delta 16-synthetase activity in human but not in rat testes. In the study of testicular function higher monkeys are increasingly used as a model for human reproduction. The availability of testes from 2 different species of macaques (rhesus and crab eating monkeys) enabled us to compare the in vitro metabolism of pregnenolone in these testes with human testes. The pattern obtained in both monkey species were very similar, but completely different from those found in man. The delta 4 pathway was the preferred route for the conversion of pregnenolone to testosterone in the monkeys tested, the delta 5 pathway in the humans. delta 16-Synthetase activity, a prerequisite for the synthesis of the sex pheromone precursors 5,16-androstadien-3 beta-ol and 4,16-androstadien-3-one, was clearly measurable in the human but not in the monkey testicular homogenates. So far, man and boar are the only species harbouring delta 16-synthetase activity in their testes. These in vitro data indicate that the nonhuman primates studied are not suitable models for the study of human testicular function.     

The synthesis of testosterone and estradiol-17beta by the gonads of neonatal rats in vitro.

The rate of synthesis of estradiol-17beta by the ovary, and of testosterone by the testis of the newborn rat have been studied in vitro using tissue homogenates. Quantitative estimation of these steroids has shown a peak of activity in the ovary between 8 and 12 days post partum of 63 pg/mg tissue/hr, compared with 6 pg/mg/hr at day 6, and 19 pg/mg/hr at day 14. Testosterone synthesis in the testis is most active on day 1 (3.1 ng/mg/hr), declining steadily to 1.1 ng/mg/hr on day 11. Adult testicular tissue under the same conditions synthesised 0.5 - 1.0 ng testosterone/mg/hr. These results are consistent with other observations which have suggested a transient period of active steroidogenesis immediately after birth in the rat, but the time during which steroid synthesis is elevated has been more clearly defined. The methods described here provide a model system for the study of synthetic steroids and other drugs which may affect the sexual differentiation of the hypothalamus by altering gonadal steroidogenesis.     

Reinitiation of spermatogenesis by exogenous gonadotropins in a seasonal breeder, the woodchuck (Marmota monax), during gonadal inactivity.

The present study was undertaken (1) to document structural and functional changes in the testes of seasonally breeding woodchuck during active and inactive states of spermatogenesis and (2) to evaluate the ability of exogenous gonadotropins to reinitiate spermatogenesis outside the breeding season. During seasonal gonadal inactivity, there were significant (P less than 0.05) reductions in volumes of several testicular features (testis, seminiferous tubules, tubular lumen, interstitial tissue, individual Leydig cells, Leydig cell nuclei, and Leydig cell cytoplasm) as compared with gonadally active animals. The diameter of the seminiferous tubules was decreased by 26%, and Leydig cell numbers also declined in the regressed testes. These changes were accompanied by a decline in testosterone (T) levels in both plasma and testis, and reduction in epithelial height of accessory reproductive organs. A hormonal regimen was developed that would reinitiate spermatogenesis in captive, sexually quiescent woodchucks. A combination of PMSG and hCG markedly stimulated testicular growth and function and restored spermatogenesis qualitatively. Quantitatively normal spermatogenesis was restored in 2 of 6 treated males. Morphometric analyses revealed substantial increases in seminiferous tubular diameter and in the volume of seminiferous tubules, tubular lumen, total Leydig cells, and individual Leydig cells in the hormone-treated animals. These increased values corresponded to 99, 75, 68, 51, and 200%, respectively, of the values measured in naturally active woodchucks. Leydig cell numbers, however, remained unchanged and approximated only 31% of the number found in naturally active testes. Hormonal stimulation also resulted in a significant rise in serum T as well as in the total content of testicular T, and a marked increase in epithelial height in various accessory reproductive glands. The most effective hormonal protocol for stimulating spermatogenesis was treatment with 12.5 IU of PMSG twice a week for 4 weeks followed by 12.5 IU of PMSG + 25 IU of hCG twice a week for 4 weeks.     

Spermatogenesis, testicular composition and the concentration of testosterone in the equine testis as influenced by season

The influence of season on spermatogenesis, testicular composition and the concentration of testosterone in the equine testis was evaluated using testes from 45 stallions. Testes were obtained through a commercial abbatoir during September, December-January, March and July. The weights of the testes, the tunica albuginea and testicular parenchyma and the proportion of the testicular parenchyma occupied by seminiferous tubules or interstitial tissue were similar during each season. How ever, diameter of the seminiferous tubules was greater in July than during other months of the study. In addition, the concentration of testosterone within the testicular parenchyma was twice as great during July as during the fall and winter, and this period of peak testicular testosterone concentrations was associated with spermatozoal production rates, which were 65% greater than those observed in September.     

Developmental appearance of the Ca2+-binding proteins parvalbumin,calbindin D-28K,S-100 proteins and calmodulin during testicular development in the rat

Summary Calcium and intracellular Ca²⁺-binding proteins are possibly involved in hormone production and spermatogenesis in rat testis. Parvalbumin, calbindin D-28K, S-100 proteins and calmodulin were localized in the Leydig cells, which are sites of testosterone synthesis. Only the appearance of parvalbumin-immunoreactivity is closely correlated to testosterone production during development of the testes. Calbindin D-28K-immunoreactivity persisted in foetal-type Leydig cells and in adult-type Leydig cells at all stages of development. S-100-immunoreactivity was low during all foetal stages, absent between birth and puberty, and increased thereafter. Calmodulin staining is most prominent in the cytoplasm of developing spermatocytes and of maturing spermatids. All four proteins co-exist in the seminiferous tubules. The distinct localization and developmental appearance of these proteins suggests different regulatory roles in Leydig cell function and spermatogenesis.     

Transport of iron and transferrin synthesis by the seminiferous epithelium of the rat in vivo

The transport of radioactive iron across the seminiferous tubules was analyzed in vivo by light-microscope quantitative radioautography. At 5 min after a single intratesticular injection of 55Fe-transferrin, a strong labeling of the basal aspect of the seminiferous epithelium was observed. Between 30 min and 2 h, the labeling on the basal aspect of the seminiferous epithelium decreased. This decrease was accompanied by a substantial increase of the radioautographic reaction over the cellular elements in the adluminal compartment. These results were consistent with the demonstration of 59Fe associated with meiotic spermatocytes and differentiating spermatids isolated by velocity sedimentation from testes injected with 59Fe-transferrin. Furthermore, after a single intratesticular injection of 59Fe-labeled human transferrin, radiolabeled rat transferrin was immunoprecipitated from homogenates of isolated tubules with a specific antibody and appeared as a single radioactive band on fluorographs of urea/polyacrylamide gels. Similarly, 59Fe-labeled rat transferrin but not 125I-transferrin was immunoprecipitated from rete testis fluids of testes infused with either 59Fe- or 125I-labeled human transferrin. Finally, the synthesis of testicular transferrin in vivo was demonstrated in fluorographs of immunoprecipitated transferrin after an intratesticular injection of 35S-methionine in rats whose livers were excluded from the general circulation by ligation of both the hepatic artery and the portal vein. Thus, our results demonstrated a unidirectional system of iron transport from the basal compartment of the seminiferous epithelium to the germ cells in the adluminal compartment involving two distinct transferrins, i.e., a serum transferrin and a testicular transferrin synthesized by the seminiferous epithelium.     

Immunolocalization and activity of aromatase in the bank vole testes.

A direct approach to identify the cellular source of P450 aromatase in the bank vole testes (seasonally breeding rodents) is the use of immunohistochemistry with a specific antibody that recognizes this enzyme. To confirm the presence of functional aromatase, its activity was measured in microsomal preparations of whole testes and of seminiferous tubules by means of biochemical assay with tritiated androstenedione. The assay was validated using increasing concentrations of both microsomal preparations. Immunoreactive aromatase was found in Leydig cells, Sertoli cells, and germ cells, especially in spermatocytes and spermatids. The aromatase activity was present in microsomal fractions of whole testis and seminiferous tubules. The immunolocalization of P450 aromatase and aromatase activity have been found as photoperiod-dependent.     

Radiation effects on rat testes. V. Studies on lysosomal enzymes (acid phosphatase and acid DNAse) and their physiological significance following partial body gamma-irradiation.

Acid phosphatase is present in the nucleus and cytoplasm of cells in the seminiferous tubules and the interstitium of rat testes. The effect of irradiation on acid phosphatase is dependent on the environmental temperature and the dose of irradiation. It appears that initial rise in the enzyme at a low radiation dose and a high environmental temperature or at a high dose and low temperature is associated with a lysosomal breakdown of the germinal cells of the testes. A decrease in acid phosphatase in the advanced stages of radiation injury is a secondary radiation effect which may lead to decreased metabolic synthesis of phosphate esters owing to the unavailability of orthophosphate in the testicular tubules. The reduced acid phosphatase activity can be detected in the seminiferous tubules, suggesting that the enzyme activity is related to the state of the germ cell population. An initial increase in acid phosphatase is matched by an initial rise in acid DNAse within hours of irradiation, further suggesting that there is radiation interaction with the cells of the germinal epithelium. The enhanced activity of DNAse following a 2nd week of irradiation at 2000 R confirms the phagocytic activity of the non-germinal cells.