Melatonin does not affect in vitro secretion of testosterone in white-footed mouse testis

Seasonal Changes in Testes Vascularisation in the Domestic Cat (Felis domesticus): Evaluation of Microvasculature, Angiogenic Activity, and Endothelial Cell Expression

Some male seasonal breeders undergo testicular growth and regression throughout the year. The objective of this study was to understand the effect of seasonality on: (i) microvasculature of cat testes; (ii) angiogenic activity in testicular tissue in vitro; and (iii) testicular endothelial cells expression throughout the year. Testicular vascular areas increased in March and April, June and July, being the highest in November and December. Testes tissue differently stimulated in vitro angiogenic activity, according to seasonality, being more evident in February, and November and December. Even though CD143 expression was higher in December, smaller peaks were present in April and July. As changes in angiogenesis may play a role on testes vascular growth and regression during the breeding and non-breeding seasons, data suggest that testicular vascularisation in cats is increased in three photoperiod windows of time, November/December, March/April and June/July. This increase in testicular vascularisation might be related to higher seasonal sexual activity in cats, which is in agreement with the fact that most queens give birth at the beginning of the year, between May and July, and in September.

Photoperiod-induced differential expression of angiogenesis genes in testes of adult Peromyscus leucopus

Non-pathological angiogenesis in adults is rare and is largely thought to be restricted to wound healing and female reproductive cycles. Adult male rodents, however, display seasonal angiogenesis to support seasonal changes in reproductive tissue morphology. Non-tropical rodents use photoperiod (day length) to determine the time of year. During short days, the reproductive system undergoes involution and mating behaviours stop, adaptations which presumably allow energy resources to be shifted to processes necessary for winter survival. We compared the patterns of gene expression involved in angiogenesis in testes of white-footed mice (Peromyscus leucopus) following 7, 14, 21 or 34 weeks of long or short day lengths. Short days decreased body mass, reproductive tract mass and seminiferous tubule diameter. Potential genes involved in seasonal angiogenesis were screened by hybridizing testicular RNA from each group to angiogenesis-specific microarrays. Genes that were ≥6-fold different between long- and short-day testes (i.e. hypoxia-inducible factor 1α(Hif1α), plasminogen activator inhibitor 1 (Serpine1), transforming growth factor β receptor 3 (Tgfβr3) and tumour necrosis factor (Tnf)) were sequenced and expression differences were compared throughout gonadal regression and recrudescence using quantitative RT-PCR. Our results suggest that short days trigger expression ofHif1α,Serpine1, andTgfβr3to inhibit angiogenesis or promote apoptosis during testicular regression, and also trigger expression ofTnfto promote angiogenesis during testicular recrudescence.

The effects of melatonin on sperm motility in vitro in Wistar rats

The effects of physiological concentrations of melatonin on motility of spermatozoa from Wistar rats were assessed in vitro. Melatonin had dose-dependent negative effects on sperm forward progression, the quality of sperm motility and on a sperm motility index. Some, but not all of these effects were due to ethanol (0.5% final concentration) which was used as a solvent for melatonin. Addition of ethanol to the incubation medium altered the pH, and increased pH had a significant negative effect on all aspects of sperm motility. Finally, the overlay of oil, which is a routine part of many sperm culture systems, had an ameliorating effect that was probably because of the lipophilic nature of melatonin.

Inhibitory effects of melatonin on testosterone but not on androstenedione production during winter in the vespertilionid bat, Scotophilus heathi

The possible effects of melatonin on testosterone and androstenedione production in vitro by testes of wild-caught bats, Scotophilus heathi, during different reproductive phases were investigated. Bats were captured during reproductive quiescent (April-August), recrudescent (September-October), breeding (November-February), and winter dormancy (late December-January) phases. Testes were incubated in media-199 for 2 h at 37 degrees C with luteinizing hormone (LH) and with or without melatonin. Melatonin had no effect on LH-induced testosterone (T) or androstenedione (A) production during the quiescent, recrudescent, and breeding phases. However, it significantly (P < 0.05) suppressed LH-induced T production but had no effect on A during winter dormancy. Testicular 17 beta-hydroxy steroid dehydrogenase (17 beta-HSD) activity was then measured in the testes from bats trapped during quiescence, breeding, and winter dormancy. Interestingly, melatonin along with LH caused suppression of 17 beta-HSD activities (3.56 +/- 0.03 unit/min/mg protein) when compared with levels of LH treated testes (7.10 +/- 1.15 unit/min/mg protein) during winter dormancy, while it had no significant effect on 17 beta-HSD activity during quiescence and breeding phases. These results suggest that in S. heathi, melatonin during winter dormancy suppresses LH-induced T production by the testes via the suppression of 17 beta-HSD activity. This may be the reason for the decline in testicular activity during winter dormancy.