Selective effect of methoxyindoles on the lymphocyte proliferation and melatonin binding to activated human lymphoid cells

Three pineal methoxyindoles (melatonin (Mel), 5-methoxytryptamine (5-MTA) and 5-methoxytryptophol (5-MTO)) were studied for their ability to influence the proliferative response of human peripheral blood lymphocytes (PBL) and tonsillar lymphocytes (TL) following activation with concanavalin A (ConA) in vitro. The ConA-stimulated DNA synthesis was affected in a different dose-dependent mode by the methoxyindoles tested. Melatonin and 5-MTO inhibited and 5-MTA increased the ConA-induced [3H]thymidine incorporation in PBL and TL. The initial screening for 2-[125I]iodomelatonin binding using a single point assay revealed significantly increased specific binding to PBL and TL after 72-h stimulation with ConA as compared to the non-activated cell cultures. Coincubation of separate lymphocyte cultures with ConA and Mel or 5-MTO resulted in inhibition of the specific 2-[125I]iodomelatonin binding (85% and 74%, respectively). The specific binding determined in the presence of 5-MTA did not differ from control values. Series of saturation and competition experiments were performed to examine the binding characteristics of ConA-stimulated lymphocytes for 2-[125I]iodomelatonin. The radioligand labelled binding sites of high affinity (Kd = 0.14 +/- 0.03 nM) and low capacity (Bmax = 6.8 +/- 1.5 fM/mg protein). Competitive studies with a variety of indoles determined the following order of relative potency for inhibition of 2-[125I]iodomelatonin binding in TL: 2-iodomelatonin > melatonin > > 5-methoxytryptophol. 5-Methoxytryptamine did not show displacement potency for the labelled ligand. Collectively, our data suggest that pineal hormones might be directly involved in the regulation of the T-lymphoproliferative response of human lymphoid cells. We show the availability of melatonin receptors, which seem to be an intrinsic characteristic of activated human lymphocyte populations. While the effects of Mel and 5-MTO can be linked to the binding sites described, it is unlikely that serotonin agonists like 5-MTA may act through the same sites to influence the mitogen-stimulated lymphocyte proliferation.

Circadian patterns of melatonin, corticosterone, and progesterone in male rats subjected to chronic stress: effect of constant illumination

Plasma and pineal melatonin and plasma corticosterone and progesterone concentrations have been shown to be altered by several types of stressors. This study was designed to define the circadian patterns of the hormones mentioned above in rats subjected to chronic stress and to investigate the influence of constant illumination. The results revealed that melatonin and corticosterone circadian patterns deteriorated and their plasma concentrations were significantly elevated. The constant illumination (2,500 lux) during the dark period (from 2000 to 0600) was not able to suppress melatonin production in stressed animals, while the plasma content of corticosterone was decreased at the end of experimental period compared to control rats. Plasma levels of progesterone were increased in stressed animals as well. Constant illumination, however, provoked also an increase of progesterone secretion in controls. Statistical comparisons between hormonal secretory patterns showed that melatonin and corticosterone correlated negatively in controls (r = -0.58, P less than 0.05) during the nighttime. However, in stressed animals correlation was observed only between melatonin and progesterone secretion during the light and dark period (r = -0.43, P less than 0.05). Surprisingly, the correlation during the nighttime in rats subjected to constant illumination was negative (r = -0.60, P less than 0.02) compared to positive correlation (r = 0.60, P less than 0.02) in rats kept under normal lighting regimen. These results suggest that melatonin release is affected by stress and, possibly, under these circumstances, interacts with adrenal steroid secretion.

In vitro effects of substance P and arginine-vasopressin on testosterone production in Leydig cells of short and long photoperiodic hamsters

The aim of the present study was to determine the interaction between substance P (SP) and arginine-vasopressin (AVP) on basal and LH-stimulated testosterone production by Leydig cells isolated from hamsters kept under long or short days (LD-hamsters, SD-hamsters, respectively). SP inhibited the testosterone production of Leydig cells, its effect being more pronounced in the case of LH-stimulated steroidogenesis in LD-hamsters. Similarly, the addition of AVP to the culture medium resulted in a diminution of basal, as well as LH-stimulated testosterone secretions. When Leydig cells were co-incubated with SP (10(-7) M) and AVP (10(-7) M), a strong inhibition of the testosterone production by 50-60% was established in LD-animals. However, even within the experimental circumstances in SD-hamsters, the modulation of testosterone production by SP and AVP was evident. The reported results suggest that there is an interference of two regulatory pathways, namely photoperiodic dependence and paracrine control of testicular steroidogenesis in hamsters.

Increase of nocturnal melatonin levels in hemodialyzed patients after parathyroidectomy: a pilot study

In hemodialyzed patients hormonal disturbances are known to occur. However, melatonin levels have not been completely studied. The aim of the study was to find whether changes in calcaemia affect melatonin secretion. For this reason we followed the nocturnal serum concentrations of melatonin and parathyroid hormone (PTH) in 9 hemodialyzed patients (6 women and 3 men, aged 37-65 years) both before and 1-3 months after parathyroidectomy at 6 p.m., 9 p.m., 11 p.m., 2 a.m., 5 a.m. and 7 a.m. At 6 p.m. blood samples to evaluate the levels of calcium and phosphate were also collected. Parathyroidectomy resulted in an increase in nocturnal melatonin levels. As expected, the parathyroidectomy was followed by considerable PTH decrease. PTH showed no nocturnal variation before or after parathyroidectomy. Calcium levels significantly decreased after the operation while phosphate levels increased. In summary, in hemodialyzed patients with hyperparathyroidism, parathyroidectomy significantly increases the nocturnal secretion of melatonin. Relationships between the pineal gland and parathyroid glands have yet to be elucidated.

Congenital anorchism: diagnostic and therapeutic aspects

Eight patients with congenital anorchism were examined and treated. Plasma LH, FSH, and testosterone concentrations and the saliva testosterone level were measured by RIA in 3 patients. The results showed a 2.75 times increase in LH level, a 1.66 times increase in FSH level, and hardly measurable serum and saliva testosterone amounts. A dynamic provocating test was applied in 4 patients by Pregnyl (2000 and 4000 IU) and the results showed absence of the gonads. The semen quality control manifested a low volume of ejaculate and aspermia. Scyntiscanning of 6 patients demonstrated no functional testicular parenchyma. Substitute androgen therapy in patients with diagnosed anorchism gave good results, which suggests that this treatment is appropriate and promising. Implantation of testiculo-prostheses by using silicon alloplastic material corrects the cosmetic defect and overcomes the physiological barrier caused by the biological inferiority complex.

hCG stimulation test for diagnosis of androgen deficiency

A diagnostic-stimulation test with hCG (Pregnyl, Organon) was developed for demonstration of latent testicular deficit. The test was worked out on clinically healthy men and was used to diagnose cases of anorchidism and cryptorchidism. This stimulation test may be applied in clinical andrology as a noninvasive and highly sensitive method.

Assessment of circulating agglutinating anti-sperm antibodies in buffalo cows with unexplained infertility and an attempt to identify buffalo sperm isoantigens

The presence of circulating agglutinating anti-sperm antibodies as cause for unexplained infertility of artificially inseminated buffalo cows was assessed. An attempt to identify buffalo sperm isoantigens was also made. The following methods were applied for that purpose: the tray agglutination test (TAT), SDS-polyacrylamide gel electrophoresis, and immunoblotting. The results obtained showed that three of 90 sera from buffalo cows with unexplained infertility were positive in TAT (3.3%) and their titers were low. A total of 27 spermatozoal polypeptides reacted positively with the IgG-isoantibodies of one of the sperm agglutinating sera in immunoblotting. Of the control sera 12 also revealed individual variations in the number of positive fractions on the blots. On the basis of comparing the blot with the positive sperm agglutinating serum to the blots of the positive controls, two buffalo sperm isoantigens were identified, with the respective molecular weights of 40 kDa and 120 kDa. In conclusion, circulating agglutinating anti-sperm antibodies are very rarely detected in buffalo cows with unexplained infertility after several artificial inseminations.

Lack of melatonin response to acute administration of nifedipine and diltiazem in healthy men

Calcium antagonists have been shown to influence some endocrinological processes in mammals. The use of calcium channel blockers in clinical practice is well documented. The current study monitored nocturnal melatonin, prolactin, and cortisol levels in 19 healthy volunteers before and after administration of calcium channel blockers. The effect of nifedipine was tested in 9 subjects, while diltiazem was administered in 10 men. The nocturnal profile of the given parameters was studied between 23:00 and 05:00 h. At midnight (zero time), the participants were given placebo, nifedipine (in a sublingual dose of 20 mg) or diltiazem (in a single dose of 90 mg). The hypothesis that calcium channel blockers decrease nocturnal melatonin secretion has not been confirmed. The mean nocturnal levels of melatonin between 01:00 and 05:00 h were: 78.1+/-8.8 (control study) vs. 82.4+/-10.2 ng/l (nifedipine study) and 73.0+/-5.3 ng/l (control study) vs. 75.1+/-5.1 ng/l (diltiazem study). In conclusion, the calcium channel blockers used in this study do not alter the nocturnal melatonin secretory process in healthy men.

Albumin microsphere as a drug delivery system for dexamethasone: pharmacokinetics in sheep, residue amount in cows and distribution in rats

The aim of this study was to evaluate the potential use of albumin microspheres as a drug delivery system to provide sustained release of dexamethasone in vivo. Pharmacokinetic studies were carried out in sheep and tissue distribution in rats given dexamethasone in two injectable forms--water suspension of dexamethasone associated with albumin microspheres and water-ethanol solution of dexamethasone. When dexamethasone was associated with albumin microspheres the amount of free dexamethasone, available for absorption did not reach the high values typical of the pattern of release of dexamethasone from water-ethanol solution. The time of withdrawal in lactating cows after i.m. administration of DXM-AM was found to be 5 days. The release of dexamethasone from the albumin microspheres was accomplished gradually thus allowing sustained levels of the corticosteroid to be maintained for several days in blood plasma, milk, liver, kidney and muscles.