Domenico Conte

Arachidonic acid and its metabolites effects on testosterone production by rat Leydig cells

Arachidonic acid (AA) seems to play an important role in testicular steroidogenesis, although controversial data exist in the literature. In the present study AA induced a dose related increase of testosterone (T) formation and, at the highest dose, stimulated the production of prostaglandin E2 (PGE2), leukotrienes B4 (LTB4) and C4 (LTC4) by purified rat Leydig cells. The contemporary addition of the prostaglandin synthesis blocker, indomethacin (IND), and AA further increased T formation, decreased PGE2 levels and did not modify LTB4 and LTC4 concentrations. The addition of a lipoxygenase inhibitor, nordihydroguaiaretic acid (NDGA, 5 μM), did not influence the stimulatory effect of AA on T and PGE2 formation while it decreasedthe output of LTB4 and LTC4. When 20 μM NDGA was used in addition to AA the expected reduction of leukotrienes release was observed together with a surprising impairment of T and PGE2 secretion. PGE2 and PGF2alpha did not modify basal T production but reduced HCG-stimulated T secretion at the 10nM dose. When 5–12-and 15-HETE were tested an enhancement of basal T formation was observed at the 10nM dose. 5-HETE (10nM) stimulated HCG-induced T production. LTA4, LTB4 and LTE4 did not influence basal T output while LTC4 and LTD4 inhibited it. LTC4 (10nM) induced a decrease of HCG-stimulated T production. These findings suggest that: 1) exogenous AA stimulates T secretion; 2) conversion of AA to cycloxygenated and lipoxygenated metabolites is not required for its steroidogenic effect; 3) cycloxygenated and lipoxygenatedcompounds play a diverse modulatory role on testicular steroidogenesis.

Pituitary adenylate cyclase-activating polypeptide regulates rat Leydig cell function in vitro

The present study was designed to evaluate the effects of both pituitary adenylate cyclase-activating polypeptide (PACAP)-27 and PACAP-38 on testosterone, cAMP and prostaglandin E2 (PGE2) production by purified rat Leyding cells. Because PACAP-38 shares homology with vasoactive intestinal peptide (VIP), the effects of VIP and both PACAP and VIP receptor antagonists on testicular steroidogenesis were also examined. PACAP-38 potentiated testosterone response to a low effective dose of human chorionic gonadotropin (hCG), while PACAP-27 was without effect. Furthermore, PACAP-38 amplified testosterone response to a wide concentration range of hCG until the submaximal dose. VIP evoked a dose-dependent increase of both basal and hCG-induced testosterone production. PACAP potentiation of steroidogenesis was nullified in the presence of a PACAP antagonist, but was not modified by a VIP antagonist. Moreover, while VIP antagonist blunted testosterone response to VIP, PACAP antagonist was without effect. Increasing concentrations of PACAP-38 evoked a dose-response enhancement of both cAMP and PGE2 production. However, this fatty acid is not involved in PACAP activity, as a prostaglandin blocker indomethacin did not modify the effect of PACAP on steroidogenesis. Taken together these findings: (i) demonstrate that PACAP-38 is able to activate both cAMP- and phosphatidylinositol-dependent mechanisms in Leydig cells; (ii) indicate that the peptide exerts an amplificatory action on testicular steroidogenesis stimulated by hCG and that this activity is receptor-mediated, as it is prevented by a PACAP receptor antagonist; (iii) predict the existence of specific PACAP receptors (type 1 binding sites) on Leydig cells.

Acetylsalicylic acid inhibits the pituitary response to exercise-related stress in humans.

PURPOSE Prostaglandins (PGs) modulate the activity of the hypothalamus-pituitary axis, and pituitary hormones are largely involved in the physiological responses to exercise. The purpose of this study was to analyze the effects of acetylsalicylic acid (ASA), an inhibitor of PGs synthesis, in the pituitary responses to physical stress in humans. METHODS Adrenocorticotropin (ACTH), beta-endorphin, cortisol, growth hormone (GH), and prolactin (PRL) responses to exercise were evaluated after administration of either placebo or ASA. Blood samples for hormone evaluations before (-30, -15, and 0 pre) and after (0 post, +15, +30, +45, +60, and +90 min) a 30-min treadmill exercise (75% of .VO(2max)) were taken from 12 male athletes during two exercise trials. One tablet of ASA (800 mg), or placebo, was administered two times daily for 3 d before and on the morning of each exercise-test. RESULTS The results clearly show that, compared with placebo, ASA ingestion significantly blunted the increased serum ACTH, beta-endorphin, cortisol, and GH levels before exercise (anticipatory response) and was associated with reduced cortisol concentrations after exercise. Furthermore, although no differences in the GH response to exercise were shown, a significantly reduced total PRL response to stress condition was observed after ASA. CONCLUSION ASA influences ACTH, beta-endorphin, cortisol, GH, and PRL responses to exercise-related stress in humans (preexercise activation/exercise-linked response). Even though it is not possible to exclude direct action for ASA, our data indirectly confirm a role of PGs in these responses. We have to further evaluate the nature of the preexercise endocrine activation and, because of the large use of anti-inflammatory drugs in athletes, whether the interaction between ASA and hormones might positively or negatively influence health status, performance, and/or recovery.

Aspirin inhibits androgen response to chorionic gonadotropin in humans

Eicosanoids play an important role in the regulation of the hypothalamic-pituitary axis; less clear is their role in testicular steroidogenesis. To evaluate the involvement of cyclooxygenase metabolites, such as prostaglandins, in the regulation of human testicular steroidogenesis, we examined the effects of a prostaglandin-blocker, aspirin, on plasma testosterone, pregnenolone, progesterone, 17OH-progesterone, androstenedione, dehydroepiandrosterone, and 17β-estradiol response to human chorionic gonadotropin (hCG) in normal male volunteers in a placebo-controlled, single-blinded study. To test the efficacy of aspirin, seminal prostaglandin E2 levels were also determined. hCG stimulation increased peripheral levels of testosterone, 17OH-progesterone, androstenedione, dehydroepiandrosterone, and 17β-estradiol, without affecting circulating pregnenolone and progesterone values. Aspirin significantly lowered seminal prostaglandin E2levels, whereas it did not modify steroid concentrations not exposed to exogenous hCG. Moreover, the drug significantly reduced the response of testosterone, 17OH-progesterone, androstenedione, and dehydroepiandrosterone to hCG, as assessed by the mean integrated area under the curve, whereas it did not influence 17β-estradiol response. In conclusion, aspirin treatment inhibits androgen response to chorionic gonadotropin stimulation in normal humans. The action of aspirin is probably mediated via an effective arachidonate cyclooxygenase block.Eicosanoids play an important role in the regulation of the hypothalamic-pituitary axis; less clear is their role in testicular steroidogenesis. To evaluate the involvement of cyclooxygenase metabolites, such as prostaglandins, in the regulation of human testicular steroidogenesis, we examined the effects of a prostaglandin-blocker, aspirin, on plasma testosterone, pregnenolone, progesterone, 17OH-progesterone, androstenedione, dehydroepiandrosterone, and 17beta-estradiol response to human chorionic gonadotropin (hCG) in normal male volunteers in a placebo-controlled, single-blinded study. To test the efficacy of aspirin, seminal prostaglandin E(2) levels were also determined. hCG stimulation increased peripheral levels of testosterone, 17OH-progesterone, androstenedione, dehydroepiandrosterone, and 17beta-estradiol, without affecting circulating pregnenolone and progesterone values. Aspirin significantly lowered seminal prostaglandin E(2) levels, whereas it did not modify steroid concentrations not exposed to exogenous hCG. Moreover, the drug significantly reduced the response of testosterone, 17OH-progesterone, androstenedione, and dehydroepiandrosterone to hCG, as assessed by the mean integrated area under the curve, whereas it did not influence 17beta-estradiol response. In conclusion, aspirin treatment inhibits androgen response to chorionic gonadotropin stimulation in normal humans. The action of aspirin is probably mediated via an effective arachidonate cyclooxygenase block.

STIMULATORY ACTION OF ENDOTHELIN-1 ON RAT LEYDIG CELLS: INVOLVEMENT OF ENDOTHELIN-A SUBTYPE RECEPTOR AND PHOSPHOLIPASE A2-ARACHIDONATE METABOLISM SYSTEM

In a previous report we have observed that endothelin-1 (ET-1) is able to stimulate testosterone (T) production by rat Leydig cells revealing an interaction with human chorionic gonadotropin (hCG). The present study was designed to further characterize the stimulatory action of ET on testicular steroidogenesis, to evaluate which subtype of ET receptors is involved in this activity and to examine the role of phospholipase A2 (PLA2)-arachidonate metabolism system in ET-1 transduction mechanism. To this purpose we investigated: i) the interaction of ET-1 with another secretagogue of T, like luteinizing hormone releasing hormone (LHRH); ii) the interference of ET(A) and ET(B) receptor antagonists (BQ-123 and BQ-788, respectively) and of inhibitors of PLA2 (quinacrine) and arachidonate lipoxygenase pathway (nordihydroguaiaretic acid:NDGA) on ET-1-induced T and PGE2 secretion from purified rat Leydig cells. Data obtained indicate that ET-1 amplified T and PGE2 response to LHRH and this secretagogue in turn potentiated testicular steroidogenesis stimulated by endothelin. The ET(A) antagonist, BQ-123, inhibited in a dose-related fashion ET-1-induced T production whereas ET(B) antagonist, BQ-788, failed to affect T response to the peptide. Furthermore, ET(A) antagonist inhibited the stimulatory effect of ET-1 on hCG- or LHRH-induced T secretion and it was able to exert a dose-dependent inhibition of ET-1-stimulated PGE2 output. Moreover, a PLA2 inhibitor quinacrine inhibited the stimulatory action of ET-1 on T production and suppressed basal and ET-1-induced PGE2 release whilst a lipoxygenase blocker NDGA did not modify T response to the peptide. Taken together these findings i) indicate additivity of effects between ET-1 and LHRH in stimulating T and PGE2 production; ii) confirm that ET(A) subtype receptors mediate the stimulatory action of ET-1 on rat Leydig cells; iii) strongly suggest that PLA2-arachidonate metabolism system is involved in endothelin transduction mechanism.

Role of seminal prostaglandins in male fertility. I. Relationship of prostaglandin E and 19-OH prostaglandin E with seminal parameters

Prostaglandin (PG)E and 19-OH PGE, now considered to be the most important of the human seminal prostaglandins, were assayed in infertile and normal men. In the 15 volunteers PGE and 19-OH PGE levels were 23-89 μg/ml and 36-106 μg/ml, respectively. In the 4 groups of infertile patients in whom either PGE or 19-OH PGE levels were increased or decreased with respect to normal, sperm concentration and motility were significantly reduced. The negative effects of low levels of seminal prostaglandins on sperm concentration and motility might be correlated respectively with decreased adenylcyclase and testicular androgen activity. The negative effects of high levels of prostaglandins on the seminal fluid might be due either to an inhibition in testicular DNA synthesis or to a decreased sensitivity of the receptors to high titers of prostaglandins.

Galanin stimulates steroidogenesis in rat leydig cells

The present study was designed to evaluate whether galanin could play a role in the regulation of testicular steroidogenesis. To this purpose, using purified rat Leydig cells, we examined the effects of galanin on basal and hCG- or LHRH-induced testosterone production and the interference of a specific galanin receptor antagonist, galantide, on galanin activity. Moreover, since it has been shown that galanin-induced stimulation of LHRH secretion appears to involve the release of prostaglandin E2 (PGE2) as intracellular mediator, we evaluated also the effect of galanin on Leydig cells PGE2 output and the interference of indomethacin, a cycloxygenase blocker, on its activity. Furthermore, the effect of nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, was also examined. Data obtained indicate that galanin amplified testosterone response to hCG or LHRH whilst galantide prevented its potentiating activity. Moreover, galanin stimulated PGE2 output though this fatty acid is not involved in galanin activity on Leydig cells as indomethacin failed to affect its amplification of testosterone production. The possible involvement of leukotrienes should also be excluded as NDGA did not modify galanin action. In summary, the present study indicates that galanin potentiates acute gonadotropin or LHRH steroidogenic action on Leydig cells and that this activity is specific and receptor-mediated as it is prevented by a specific receptor antagonist.

Role of seminal prostaglandins in male fertility. II. Effects of prostaglandin synthesis inhibition on spermatogenesis in man

The effect of prostaglandin biosynthesis inhibition has been studied in two groups of infertile Oligozoospermic patients with high or normal-low seminal prostaglandin (PG) levels. PGE and 19-OH PGE were assayed by means of a gaschromatographic method and the most important seminal parameters (volume, concentration, motility and morphology of spermatozoa) were evaluated in basal conditions and at the end of indomethacin treatment, at a daily oral dose of 100 mg for thirty days. Adropin prostaglandin levels following indomethacin was observed in both groups of patients but only in the group with high concentrations of prostanoid derivates the prostaglandin inhibition was correlated with a significant improvement in sperm count and motility.

Failure to stimulate melatonin synthesis in the rat pineal gland with an adenosine analog

Recent studies indicate the presence of adenosine binding sites in rat pinealocytes and an effect of their activation on pineal serotonin metabolism. However, controversial data exist, and reports suggest that the role of adenosine in pineal physiology is complex. On this basis, we evaluated the effects of an adenosine analog (N-ethyl-carboxamido-adenosine: NECA) on in vitro and in vivo melatonin production in the rat pineal gland. In the in vitro protocol, pineals were incubated with NECA (0.5 mM, 1 mM, or 2.5 mM) or isoproterenol (ISO: 10(-6)M) for 4 hr. In the in vivo experiments, animals were given NECA (1 mg/kg IP), ISO (0.5 mg/kg IP) or 1 ml saline diluent and sacrificed 2 hr later. The samples were assayed for pineal N-acetyltransferase (NAT) activity and melatonin concentrations. ISO caused the expected marked rise in NAT activity and melatonin levels in both protocols. NECA was ineffective in causing any modification of the parameters measured. We conclude that the adenosine analog NECA may not be involved in the activation of melatonin production. These data contrast with others in which NECA administration resulted in an increase in melatonin levels. The participation, if any, of the purinergic system in the physiology of the pineal gland is still far from being characterized.

ACTH 1–17 and sexual behavior

SummaryThe influence of the administration of ACTH 1–17 on the sexual behavior has been studied in a group of male patients affected by psychogenic impotence, i.e. without any detectable organic reason for such disturbance. The administration of the drug led to a notable increase in the sexual performance of the patients. By the way, all the hormonal parameters taken into account (gonadotropins, sexual steroids, adrenal steroids, etc.), were not affected by the treatment. The AA, conclude therefore that the beneficial effect of the ACTH 1–17 on the sexual behavior was due to a direct action on the CNS and was not hormone-mediated.