The paracrine role played by interleukin-1 alpha in the testis.

Interleukin-1alpha (IL-1alpha) plays an important role(s) in the regulation of immune and inflammatory responses. The testis is an immunologically privileged organ and the variety of effects exerted by IL-1alpha on this organ have yet to be explored in detail. The aim of the present review is to describe our current view of the paracrine role played by IL-1alpha in testicular physiology. Testicular IL-1alpha is expressed during development, primarily in Sertoli cells, appearing in rats for the first time 20 days after birth. This cytokine is microheterogeneous, consisting of three molecular species with molecular weights of 45, 24 and 17 KDa. The 17 KDa form represents mature IL-1alpha, while the 24-KDa IL-1alpha has been shown by our research group to be an alternately spliced form of the 45-KDa pro-IL-1alpha. IL-1alpha was observed to stimulate the proliferation of immature Sertoli cells with higher efficacy than FSH. IL-1alpha was also found to exert mitogenic effects both on isolated peritubular cells and germ cells. Furthermore, isoforms of IL-1alpha were seen to stimulate basal testosterone production in immature Leydig cells, but not in the corresponding adult cells. This effect involved induction of the steroidogenic acute regulatory (StAR) protein and positively regulation by p38 MAPK. Recently, we have observed positive interactions between IL-1alpha and hormones of the GH/IGF-I system that lead to enhanced androgen production by the Leydig cell. In conclusion, our findings suggest that isoforms of IL-1alpha may serve as paracrine mediators, alone or in concert with other factors, that support proper testicular cell functioning and, thereby, reproduction and fertility.

Melatonin and maturation pace in female three-spined stickleback, Gasterosteus aculeatus.

In many animals sexual maturation is controlled by the photoperiod. In mammals, the photoperiodic message is mediated via melatonin, but it is unclear whether this also applies to fishes. Administration of melatonin via the water on a schedule aimed at mimicking a short nonstimulatory photoperiod cycle has been found not to inhibit maturation in male three-spined sticklebacks, Gasterosteus aculeatus, kept under stimulatory long photoperiods. To study whether melatonin affects maturation pace, adult female sticklebacks kept under stimulatory photoperiodic regimes of Light:Dark (LD) 24:0 h (Exp. 1) or LD 16:8 h (Exp. 2) and 18 degrees were treated with melatonin (0, 20, or 80 microg/L water) via the water for 16 h per day. In addition, females were also kept under a nonstimulatory short photoperiod (LD 8:16). The time at which full maturation was achieved (running roe) was noted and the ovaries of nonovulated fish were studied histologically. Most fish under LD 24:0 and LD 16:8 matured (maturation rates in Exp. 1 and 2, respectively: control, 100 and 86%; low-dose melatonin, 83 and 93%; high-dose melatonin, 90 and 75%), whereas almost all females kept under LD 8:16 remained immature (maturation rates: 0% in Exp. 1 and 3% in Exp. 2). There was no difference in maturation pace, proportion of fish maturing, or relative ovarian weights between controls and melatonin-treated fish kept under LD 16:8. Furthermore, there was no difference in proportion of fish maturing or relative ovarian weights between controls and melatonin-treated fish kept under LD 24:0. However, LD 24:0 controls matured significantly earlier than fish receiving the high melatonin dose. Thus, there was an inhibitory effect of the high melatonin dose on maturation pace under LD 24:0. Nevertheless, this effect was small compared to the inhibitory effect of LD 8:16 treatment, suggesting that at least in this season, the major part of the photoperiodic effects in the stickleback is mediated via mechanisms other than circulating melatonin.

Feedback control of gonadotropins in Atlantic salmon, Salmo salar, male parr.I. Castration effects in rematuring and nonrematuring fish.

Sexual maturation of Atlantic salmon (Salmo salar) male parr is a seasonally recurrent "all or none" response; either a fish matures fully or it does not mature. To study whether gonadal feedback on gonadotropic hormones, GTH I and GTH II, is involved in the control of maturation, previously mature Atlantic salmon male parr were either sham-operated or castrated in spring. They were then sampled during the onset of gonadal growth (late June-early July) or shortly before the breeding season (late September). In autumn, sham-operated males separated into two groups: nonrematuring males with low pituitary and plasma levels of both GTH I and GTH II, and those rematuring with high levels of gonadotropins. Castrated males had low GTH I and GTH II plasma and pituitary levels, similar to those of the nonrematuring fish, suggesting positive feedback mechanisms, separating the sham-operated fish into low and high GTH level groups. In the summer, plasma GTH II was nondetectable in all fish. Pituitary GTH II content was lower in nonrematuring, than in rematuring males and was even lower in castrated fish. In contrast, castration increased pituitary and plasma levels of GTH I in the summer, suggesting a negative feedback at this reproductive stage. There were no significant differences in immunoassayable levels of GTH I in plasma in rematuring and nonrematuring sham-operated males at this time. The control of rematuration is complex and may involve factors other than circulating GTH I levels, possibly with differences in gonadal sensitivity to GTH I.

Melatonin does not prevent long photoperiod stimulation of secondary sexual characters in the male three-spined stickleback Gasterosteus aculeatus.

Breeding in the three-spined stickleback is stimulated by long but not by short photoperiods in many seasons. The aim of the present study was to test the hypothesis that melatonin plays a role in the inhibitory effect of short photoperiod in this species. Adult nonbreeding males were kept either under constant light (Experiment 1) or under a stimulatory long photoperiod (16L 8D, Experiment 2), in water containing 0, 20, or 80 microg/liter melatonin for 16 hr/day for 28 days during the spring. These melatonin treatments were intended to simulate the daily melatonin pattern of a nonstimulatory short photoperiod. In the second experiment, fish were also kept under a nonstimulatory short photoperiod (8L 16D). In the natural breeding season the only germ cells found in the stickleback testes are spermatozoa and spermatogonia, a condition found in many fish under all treatments. In the first experiment, spermatogenesis was not influenced by melatonin. However, testes also containing spermatocytes and spermatids were more common in fish kept under 8L 16D and fish treated with 80 microg/liter melatonin than in 16L 8D controls in Experiment 2. Kidney hypertrophy, an androgen-dependent male secondary sexual characteristic in the stickleback, appeared in most males kept under constant light or 16L 8D and was not influenced by melatonin treatment. In contrast, control males kept under 8L 16D in Experiment 2 did not display kidney hypertrophy. Therefore, the presence of an extended period of elevated melatonin did not prevent the stimulatory effects of long photoperiod on development of this secondary sexual characteristic in the stickleback.