Inhibitory effect of estradiol-17 beta on human chorionic gonadotropin-induced increment of testicular blood flow and plasma testosterone concentration in rats

Testicular haemodynamics, plasma testosterone and oestradiol concentrations, and serum nitric oxide levels in the Egyptian buffalo bull after a single administration of human chorionic gonadotropin

This current study aimed for the first time to evaluate the effect of a single intravenous administration of human chorionic gonadotropin hormone (hCG) on the testicular artery haemodynamics measurements (resistance [RI], and pulsatility indices [PI]), plasma steroids (estradiol-17β and testosterone) and nitric oxide (NO) levels in buffalo bulls. Twelve Egyptian buffalo bulls weighted 450 ± 20 kg were randomly divided into the hCG group (n = 6) and injected a single dose with Ovogest (EPIFASI; 5,000 IU, iv), whereas the others (n = 6) were injected with normal saline and served as controls. Doppler evaluation and blood sampling were performed just before the administration (hour 0) and at 1, 2, 4, 6, 8, 10, 24 and 28 hr after administration. Bulls in the control group did not show any alterations in hormonal levels and blood flow parameters (p > .05). In the hCG group, RI was declined (p < .05) in 6 hr post-administration (0.31 ± 0.01 versus 0.45 ± 0.01), while PI was declined (p < .05) later in 10 hr (0.74 ± 0.01 versus 1.23 ± 0.02). Additionally, testicular blood flow was increased (p < .05) 8 hr (42.02 ± 1.02 ml/min/100 g versus 31.34 ± 0.88 ml/min/100 g) after administration. Testosterone and NO levels were (p < .05) increased at 4 and 6 hr post-administration (3.55 ± 0.03 ng/ml versus 2.84 ± 0.01 ng/ml, and 55.32 ± 4.25 µmol/L versus 32.21 ± 1.55 µmol/L), whereas oestradiol levels were elevated (p < .05) in 6 hr (31.25 ± 0.08 pg/ml) only post-administration then declined. In conclusion, the single intravenous administration of hCG triggered many alterations in the supratesticular artery vascularization and hormonal profile that could affect positively on steroidogenesis and testicular function in buffalo bull.

Amifostine protective effect on cisplatin-treated rat testis

Cisplatin is a potent drug used in clinical oncology but causes spermatogenesis damage. Amifostine is a drug used against toxicity caused by ionizing irradiation and chemotherapeutic drugs. Since cisplatin provokes fertility and induces germ cell apoptosis and necrosis, we proposed to evaluate the amifostine cytoprotective action on testes of cisplatin-treated rats. Thirty-day-old prepubertal Wistar rats received a single cisplatin dose of 5 mg/kg and were killed after 3, 6, and 12 hr. The hematoxylin-eosin stained testicular sections were submitted to histological, morphometric, and stereological analysis. The terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphosphate nick end-labeling (TUNEL) method was used to label apoptotic cells. TUNEL-positive and TUNEL-negative germ cells with abnormal nuclear morphology (ANM) were scored. Significant alterations of greater part of the parameters occurred in the cisplatin-treated group (CE) compared to the group that received amifostine before the cisplatin-treatment (ACE); however, testicular weight and volume did not vary between these groups. Tubular diameter was reduced in CE in comparison to ACE rats, while interstitial tissue and lymphatic space volume and volume density were significantly higher in CE rats; interstitial testicular edema probably occurred in cisplatin-treated rats. CE rats showed important histological alterations, which were more accentuated than in ACE rats. The numerical densities of apoptotic germ cells and TUNEL-negative cells with ANM were lower in ACE than in CE rats. In conclusion, the amifostine previously administered to prepubertal rats reduced the testicular damage caused by cisplatin. We conclude that amifostine partially protected the rat seminiferous epithelium against cisplatin toxicity.

Testicular blood flow and plasma concentrations of testosterone and total estrogen in the stallion after the administration of human chorionic gonadotropin

The goal of this study was to investigate for the first time a possible association between plasma concentrations of testosterone and total estrogen and testicular blood flow in the stallion. Correlations between these variables were calculated before and after administration of human chorionic gonadotropin (hCG). Eight mature warmblood stallions received 5,000 IU hCG intravenously, and four stallions received solvent only. Testicular blood flow in the left and right testicular arteries was assessed using colour Doppler sonography by measuring blood flow volume (BFV) and pulsatility index (PI) immediately before (time 0) and 1, 3, 6, 12, 24, 72, 120 and 168 h after hCG administration. EDTA blood samples were collected after each examination from a jugular vein to measure plasma testosterone and total estrogen concentrations. After treatment, the BFV increased and was elevated at 1 h and between 12 and 24 h. The profile of the PI was contrary to that of the BFV throughout the study period. Following hCG, there was a biphasic increase in testosterone concentration with maxima between 1 and 3 h and between 24 and 72 h, and there was a monophasic increase in the total estrogen concentration with a maximum between 6 and 24 h. At time 0, the total estrogen concentration correlated significantly with BFV (r=0.90; P<0.05) but the testosterone concentration did not (P>0.05). The testosterone and total estrogen concentrations did not correlate with PI (P>0.05). The total estrogen concentration, but not testosterone, correlated well with BFV after injection of hCG (P<0.05). The results of this study indicated that the testicular blood flow volume of the stallion may be regulated by estrogens, but additional studies are necessary to investigate whether there is a causal relationship.

Age-related differences in testicular microcirculation

Different aspects of testicular microcirculation were studied in rats aged 20, 24 or 90 days, in order to determine if maturational changes in the testis could influence its vasculature. Using laser Doppler flowmetry, it was found that vasomotion was not present in 20-day-old rats, but it could be induced by hCG-treatment given 32 h prior to flow measurements. In rats aged 24 days vasomotion was present in the testis but it was not influenced by hCG treatment, in contrast to adult rats in which testicular vasomotion disappeared after hCG treatment. In all age-groups, hCG treatment induced an increase in testicular interstitial fluid (IF) volume, which was most pronounced in young rats. In young rats, as in adults, there was an increase in the volume density of polymorphonuclear (PMN) leucocytes in testicular blood vessels after hCG treatment. However, rats aged 20 or 24 days did not exhibit any significant extravascular migration of leucocytes as occurred in adult rat testis after hCG injection. The deposition of colloidal carbon particles observed in adult rats after hCG-treatment was also not seen in young rats. It is concluded that the vasculature of the immature rat testis responds to hCG stimulation with an increase in IF volume. However, when compared to adult rats, different mechanisms may be operating because no evidence for opening of inter-endothelial cell gaps was observed in the testis of young rats.

Effect of an LHRH-agonist on testicular microcirculation in hypophysectomized rats

The effect of an LHRH-agonist on testicular vasomotion was studied in adult hypophysectomized rats. At 0.5 and 1 h after injection of 1 microgram LHRH-agonist, no effect on vasomotion was observed, but after 2 h the pulsatile blood flow pattern had changed to continuous flow in 50% of the rats. At 4 h after treatment with LHRH-agonist, vasomotion was not detected in the testis of any rat. In addition, at the latter time an increased number of polymorphonuclear leucocytes (PMNs) were observed in testicular microvessels, and some PMNs had migrated into the interstitial space. These findings are discussed in relation to the well-known stimulatory effect of LHRH-agonists on testicular interstitial fluid volume.

Testicular vascular resistance in the rat after intratesticular injection of an LRH-agonist

Testicular vascular resistance (TVR) was estimated 1, 2, 4 and 8 h after unilateral intratesticular injection of 1 or 10 ng of an LRH-agonist (A). The lower dose had no effect on plasma levels of testosterone or LH, but there was a significant increase in TVR 2 h after injection when compared to the vehicle-injected contralateral testis. Injection of 10 ng LRH-A induced an increase in plasma levels of LH at 1 and 2 h after treatment and in the plasma levels of testosterone at 1, 2 and 4 h. In the same rats there was a decrease in TVR at 2, 4 and 8 h after LRH-A treatment compared to the contralateral testis. It is concluded that LRH-A can have both stimulatory and inhibitory effects on TVR in the rat and that the direction of this effect may be related to the ambient level of LH.

Luteinising hormones activate a factor(s) in testicular interstitial fluid which increases testicular vascular permeability

The mechanism by which hCG increases the rat testicular vascular permeability was studied by injecting the testes with hCG (0.1-100 ng) together with testicular interstitial fluid (150 mul) or with the fluid alone (control) and measuring the uptake of i.v. injected [125I]hCG and the interstitial fluid volume in the testes. Both parameters were already increased with 1 ng of hCG and maxima were seen with 2 ng of hCG. The effect of hCG was not inhibited by injection of a 1000-fold excess of deglycosylated hCG together with hCG. No increase was seen after injection of 2 ng of hCG in saline or in rat serum. The response was specific to luteinising hormones since only rLH mimicked the effect of hCG, but deglycosylated hCG, rFSH or rat prolactin did not. Denaturation of the fluid or addition of serine protease inhibitor (p-aminobenzamidine) to the fluid prevented the effect of hCG. Treatment of the hCG-activated fluid with anti-hCG gamma-globulin Sepharose did not abolish the permeability effect of the fluid. This, and the finding that hCG is not catabolised during incubation in the fluid, suggests that hCG itself is not transformed to a vasoactive compound in the fluid. These results strongly suggest that luteinising hormones activate a factor(s) in rat testicular fluid which mediates their permeability effect. The putative factor(s) seems to be heat-sensitive with a molecular weight of over 10 000 Da.

Testicular microcirculation in the rat studied by videophotometric capillaroscopy, fluorescence microscopy and laser Doppler flowmetry

Testicular capillary blood flow was studied in rats using laser Doppler flowmetry, in vivo fluorescence microscopy and videophotometric capillaroscopy. All the methods revealed rhythmical oscillations in testicular microcirculation with a periodicity of 4-10 c.p.m. In arterioles, capillaries and small post-capillary vessels, periods of continuous blood flow alternated with periods of no or very low flow. No visible leakage of dextran-150 was observed from the testicular blood vessels. Four, 8 and 16 h after an s.c. injection of 200 IU hCG the blood flow was continuous and there was leakage of dextran-150 from the microvessels to the interstitial tissue. Twenty-four and 32 h after hCG the blood flow pattern was again rhythmical, and at 32 h there was no leakage of dextran-150. This suggests that hCG induces changes in blood flow and transvascular fluid exchange in the testis, perhaps by altering smooth muscle activity at the arteriolar-level.

Paracrine control of the testis

The mammalian testis is under the overall control of pituitary gonadotropins but the utilization of these signals to achieve normal testicular function involves complex local interactions between the Sertoli and germ cells, the Sertoli and peritubular cells, and the Sertoli and Leydig cells as well as local control of the testicular vasculature. These interactions serve two purposes: (1) to coordinate the functions of the three testicular compartments (seminiferous tubules, interstitium and the vasculature); and (2) to control the complex but orderly sequence of events that constitutes the spermatogenic cycle. This process, which involves multiplication, differentiation and translocation of the germ cells is organized into a sequence of stages, each of which is composed of a constant association of germ cells at four or five different stages of development. At each stage of the spermatogenic cycle, different events occur and the function of the Sertoli cells alters, probably in accordance with the changing requirements of the associated germ cells. As yet, our understanding of these many local events is extremely limited, particularly with respect to the identity of the hormones/factors involved in controlling the various processes. Our knowledge of paracrine control mechanisms in the testis is derived mainly from studies of the rat, but as the process of spermatogenesis is essentially the same in most mammals and involves the same sequence of events, then findings in the rat can probably be applied in general, if not in detail, to the human testis; the limited direct information available on the human testis supports this view. As most cases of infertility in men occur despite normal or raised serum gonadotropin levels and are characterized by the production of reduced or normal numbers of sperm, then it seems likely that malfunction of one or more of the intricate paracrine processes within the testis may be involved in the aetiology of idiopathic oligospermia. It is therefore argued that advances in our knowledge of the paracrine control of the testis should have major repercussions on our ability to understand, and eventually treat, idiopathic infertility in men, and also to induce infertility for contraceptive purposes.

Effects of human chorionic gonadotrophin, oestradiol and estromustine on testicular blood flow in hypophysectomized rats

The effects of human chorionic gonadotrophin (hCG), eostradiol benzoate (E2) and estromustine (Eo) on testicular and prostatic blood flow and plasma levels of testosterone were studied in hypophysectomized rats. Daily injections of 5 IU hCG induced a significant increase in testicular blood flow when measured after 8-9 days treatment. This stimulatory effect was inhibited by concomitant injection of E2 (50 micrograms/day) but not by Eo. In contrast, the stimulatory effect of hCG on plasma levels of testosterone was inhibited by administration of E2 as well as by Eo. This inhibition was correlated with decreased blood flow to the prostate. The present study gives further support to the hypothesis the oestrogens have direct effects on the testis and prostate.

Stimulatory effect of an LHRH-agonist on testicular blood flow in hypophysectomized rats

The effect of an LHRH-agonist (A) on testicular blood flow and plasma testosterone levels was studied in adult hypophysectomized rats. Subcutaneous injection of 1 microgram LHRH-agonist 2 or 4 h prior to experiment induced an increase in testicular blood flow. (

CONTROLS

21.1 +/- 2.8 ml/100 g X min; LHRH-A + 2 h: 28.9 +/- 3.3 ml/100 g X min; LHRH-A + 4 h: 32.4 +/- 4.1 ml/100 g X min P less than 0.05; all mean +/- SEM). There was also a significant increase in plasma testosterone levels at 2 h (P less than 0.01) and 4 h (P less than 0.01) after treatment with the LHRH-agonist, with a peak at 2 h.

Testicular blood flow in young and old rats and influence of hCG

To evaluate the influence of age, testicular capillary blood flow (TCBF) was measured, using the microsphere technique, in rats 3 to 24 months old, under basal conditions and after hCG stimulation (10 IU/d for two days). Despite a decline in plasma T levels, testicular capillary blood flow did not decrease with age, and hCG stimulation resulted in similar increases of approximately 50% (P less than 0.01) in testicular capillary blood flow in all age groups. We concluded that the age-associated decrease in testosterone secretion in rats is not the consequence of a decreased testicular blood flow.

Effects of testosterone, estradiol, aromatase inhibitor, gonadotropin and prolactin on the response of mouse testes to acute gonadotropin stimulation

These studies determined the local acute responsiveness of the testis to intratesticular administration of human chorionic gonadotropin (hCG) under basal, stimulated (systemic hCG pre-treated), hypogonadotropic (steroid pre-treatment) and hyperprolactinemic conditions in male mice. In addition, testicular testosterone (T) levels were determined after intratesticular administration of the aromatase inhibitor, 4-hydroxyandrostenedione (4-OHA) or progesterone under basal or hCG-stimulated conditions. Intratesticular administration of 0.025, 0.25, 2.5 or 25 mIU hCG resulted in a dose-dependent (3- to 14-fold) increase in testicular T concentrations in hCG compared to vehicle-injected testes. Systemic (i.p.) pre-treatment with 5 IU hCG 24 h before prevented any further increases in the already elevated (10-fold basal) T levels after direct intratesticular hCG injection. Pretreatment with 250 micrograms testosterone propionate (TP) reduced basal testicular T concentrations, but resulted in increased responsiveness to intratesticular hCG administration. In contrast, estradiol benzoate (EB) pretreatment, which also reduced basal testicular T concentrations, did not affect the testicular responsiveness to hCG. Hyperprolactinemia reduced testicular responsiveness to intratesticular administration of 0.025, 0.25 or 2.5 mIU hCG, but basal levels of testicular T were elevated. One hour after intratesticular injections of an aromatase inhibitor, 4-OHA; (0.25 micrograms) testis, T levels were increased in males pre-treated with 5 IU hCG (i.p.) 24 h earlier. Higher doses of 4-OHA (2.5, 25 or 250 micrograms) resulted in significant, dose-related increases in basal testicular T levels which were attenuated by hCG-pre-treatment. Intratesticular administration of 20 micrograms progesterone increased testicular T concentrations 2.7-fold, but this effect was attenuated (1.5-fold) in hCG-pre-treated mice, suggesting that enzymatic lesions beyond progesterone may be involved in hCG-induced testicular desensitization. These results indicate that testicular responsiveness to hCG depends on the existing levels of gonadotropic stimulation. However, it is evident that estrogens and prolactin also influence the sensitivity of the testis to gonadotropin.