Melatonin effects on prolactin secretion in pituitary-grafted male rats

Neuregulin 1 mitigated prolactin deficiency through enhancing TRPM8 signaling under the influence of melatonin in senescent pituitary lactotrophs

The age-related alterations in pituitary function, including changes in prolactin (PRL) production contributes to the systemic susceptibility to age-related diseases. Our previous research has shown the involvement of Nrg1 in regulating the expression and secretion of PRL. However, the precise role of Nrg1 in mitigating the senescence of pituitary lactotrophs and the underlying mechanisms are yet to be comprehended. Here, data from the GEPIA database was used to evaluate the association between transient receptor potential cation channel subfamily M member 8 (TRPM8) and PRL in normal human pituitary tissues, followed by immunofluorescence verification using a human pituitary tissue microarray. TRPM8 levels showed a significant positive association with PRL expression in normal human pituitary tissues, and both TRPM8 and PRL levels declined during aging, suggesting that TRPM8 may regulate pituitary aging by affecting PRL production. It was also found that treatment with exogenous neuregulin 1 (Nrg1) markedly delayed the senescence of GH3 cells (rat lactotroph cell line) generated by D-galactose (D-gal). In addition, melatonin reduced the levels of senescence-related markers in senescent pituitary cells by promoting Nrg1 / ErbB4 signaling, stimulating PRL expression and secretion. Further investigation showed that Nrg1 attenuated senescence in pituitary cells by increasing TRPM8 expression. Downregulation of TRPM8 activation eliminated Nrg1-mediated amelioration of pituitary cell senescence. These findings demonstrate the critical function of Nrg1 / ErbB signaling in delaying pituitary lactotroph cell senescence and enhancing PRL production via promoting TRPM8 expression under the modulation of melatonin.

Effect of exogenous melatonin on endocrinological profiles, biochemical and antioxidant and oxidative stress profiles in post-partum anestrus Andaman local buffaloes (Bubalus bubalis) in tropical island ecosystem

Andaman local buffalo (ALB) is distributed in Andaman and Nicobar Islands. ALB is non-descriptive and represents admixture of different Indian breeds of buffaloes. ALB is suffering infertility due to anestrus in dry (summer) season. Therefore, this study was conducted to assess the effect of slow release subcutaneous exogenous melatonin (MT) implant on hematological profiles, endocrinological profiles (cortisol and prolactin), biochemical profile (total protein, albumin, globulin, glucose and total cholesterol), antioxidant profiles [total antioxidant capacity (TAC), catalase (CAT), glutathione (GSH) and superoxide dismutase (SOD)] and oxidative stress profile (malondialdehyde; MDA) in anestrus buffalo cows during summer to improve its reproductive efficiency. Experimental buffaloes (5–7 years of age) were selected and divided into two groups, Gr I: Control (n=6) and Gr II: Treatment (n=6; melatonin implant @ 18 mg/50 kg b.wt). Statistical analysis revealed that these experimental profiles differed significantly between treatment and control groups. Blood profiles revealed that anestrus buffalo suffered severe macrocytic hypochromic anemia with increased leukocytosis and MT has improved the health status of reproductive system and whole body systems. Concentration of cortisol and prolactin were lower in MT treated than in control group. Similarly, antioxidant profiles were higher and oxidative stress profile was lower in MT treated group than in control group. Biochemical profiles were increased in MT treated than in untreated buffalos. Study concludes that melatonin had significant beneficial effects in improvement of the antioxidant profiles, minimization of oxidative stress with cascading beneficial effects on hormone, biochemical and hematological profiles, which will improve the cyclicity and fertility rate in anestrus buffalo during summers in humid tropical island ecosystem.

Daily and seasonal rhythmic secretary pattern of endocrinological profiles in mithun bull

Mithun (Bos frontalis) is a unique domestic free-range bovine species available in North Eastern hilly (NEH) regions of India and is reared for its protein rich meat. Mithun suffers severe non-cyclical population fluctuations; however, it is not yet declared as endangered species. Mithun follows some sort of seasonality based on the calving trend and semen production, although it is a perennial breeder. However, there is need to study the rhythmic changes of endocrine profiles to understand the hormone flow pattern in mithun to select the suitable time for blood collection to assess the exact endocrine profiles and to select the suitable time for natural breeding or semen collection by artificial methods for further research, conservation and propagation of its germplasm. Therefore, the present study was designed to evaluate the reproductive as well as metabolic endocrinological profiles in 24:00 h in intact adult mithun bulls during different seasons (winter, spring, summer and autumn) to know the rhythmic changes and flow pattern of the endocrinological profiles to improve its reproductive efficiency. Experimental mithun bulls (n = 6; age: 5-6 years; body condition score: 5-6 out of 10, classified as good) were selected for the study. Endocrinological profiles, follicle stimulating hormone (FSH), luteinizing hormone/interstitial cell stimulating hormone (LH/ICSH), testosterone, cortisol, thyroxine (T4), insulin like growth factor-1 (IGF-1), prolactin and melatonin (MT) were estimated at 04:00 h interval for one whole day in four seasons. The analysis was completed in two different ways as different times of collection (08:00, 12:00, 16:00, 20:00, 24:00 and 04:00 h) and day (08:00 to 16:00 h) & night time (20:00 to 04:00 h) collections. Repeated measures ANOVA analysis revealed that the bulls in winter and spring had significantly (p < 0.05) higher FSH, LH, testosterone, T4, IGF-1 and MT than those in summer whereas the bulls in summer had significantly higher cortisol and prolactin than those in winter and spring seasons. Similarly FSH, LH, testosterone, T4, IGF-1 and MT were significantly (p < 0.05) higher in night than in day time collections whereas cortisol and prolactin were significantly (p < 0.05) higher in day than in night time collections in different seasons. Correlation analysis revealed that FSH, LH, testosterone, T4, IGF-1 and MT had significant (p < 0.05) positive correlation with each other whereas these had significant (p < 0.05) negative correlation with cortisol and prolactin. The study concludes that season and time of blood collection had significant effect on the endocrinological profiles in mithun bulls. Estimation of FSH, LH, testosterone, T4, IGF-1 and MT during night time and cortisol and prolactin during day time was more appropriate to get correct value of the endocrinological profiles. Spring and winter have significantly greater beneficial effects than summer on reproduction and artificial breeding programs in mithun species in the semi-intensive management in the present location.

Prenatal melatonin exposure influences the maturation of gonadotropin and prolactin estradiol-benzoate feedback system

Gonadotropin and prolactin response to estrogen feedback in female rat offspring of control and melatonin treated (150 microg/100 g BW) mother rats during pregnancy (MEL-offspring) were studied at these periods: infantile, prepubertal and pubertal. In controls negative or absent LH feedback developed after estradiol benzoate (EB) injection up to 30 days of age indicating that the onset of puberty had not occurred. The positive feedback was established from day 33 on. However, in MEL-offspring the first activation of gonadotropin secretion during afternoon, 31 h after EB, was observed at 25 days of age, representing the first neuroendocrine sign of the onset of puberty. This positive response disappeared on day 30 in MEL-offspring. At 33 days of age, the LH positive response to EB was found in both groups, indicating a more advanced sexual development. In controls, this response increased at 35 days of age while in MEL-offspring it was highly depressed. FSH secretion in response to EB showed a negative feedback effect from infantile to the end of prepubertal period in both groups. The positive feedback was observed earlier in MEL-offspring (at 33 days of age) than in controls (at 35 days of age), but at this age it was absent in MEL-offspring. A positive prolactin response to EB at all ages in controls was observed. The typical pulsatility with higher values in the afternoon appeared by the first time at 30 days of age. However, in MEL-offspring no pulsatile response was observed throughout any age. These data suggest that prenatal melatonin administration altered gonadotropin and prolactin response to EB inducing precocious sensitivity during prepubertal period but depressed response during the pubertal period.

Effect of melatonin on serum cholesterol and phospholipid levels, and on prolactin, thyroid-stimulating hormone and thyroid hormone levels, in hyperprolactinemic rats

The effects of melatonin treatment and pituitary transplants on serum total and free cholesterol levels, cholesterol esterification index, phospholipid levels and prolactin, thyroid-stimulating hormone (TSH), thyroxine (T4) and triiodothyronine (T3) levels were examined in rats. Male rats were grafted an anterior pituitary under the kidney capsule or were sham-operated on day 30th of life. Thirty days later, the rats received 4 daily s.c. injections of melatonin (25, 50 or 100 microg/rat) or vehicle, 2 h before lights off, and were killed 15 h after the last injection, and after a 24-hour fasting period. In pituitary-grafted rats, a decrease in serum free cholesterol with unmodified total cholesterol levels, and thus an augmented cholesterol esterification index, occurred. Pituitary-grafted rats showed also an increase in serum phospholipids. In control, but not in pituitary-grafted rats, melatonin injection decreased free cholesterol without modifying total cholesterol levels. Melatonin treatment (50 microg/day or greater) normalized the augmented serum phospholipid levels found in pituitary-grafted rats and increased serum phospholipids in control rats. Melatonin injection also reduced the high serum prolactin and T3 levels found in pituitary-grafted rats, and decreased T4 concentration in control rats. Neither melatonin nor pituitary grafts modified serum TSH concentration. The results demonstrate that melatonin counteracts in part lipid disturbances of hyperprolactinemic rats and lowers free plasma cholesterol and augmented serum phospholipids in control rats.