Presence of neurophysins I and II in the human pineal gland: comparison with the content of neurohypophyseal hormones

Effects of melatonin on water metabolism and renal function in male Syrian hamsters (Mesocricetus auratus)

The pineal indoleamine, melatonin, has been shown to influence many physiological systems within the mammalian body. Few studies, however, have examined the influence of melatonin on renal function. This study investigated the effects of melatonin on water metabolism and renal function. Young adult male Syrian hamsters were maintained on a long photoperiod (LD 14:10) in metabolic cages. The animals received daily (1700) injections of either control vehicle or 25 micrograms of melatonin for 85 consecutive days. Melatonin administration resulted in significant increases in water consumption and urine production. Water budgets were also significantly influenced by melatonin, as were urinary osmolality, urinary sodium, and potassium concentrations, but urinary calcium concentrations were essentially unaltered. When excretion rates for sodium, potassium, and calcium were calculated, no differences were observed between the vehicle control and melatonin-treated groups. Injections of melatonin also significantly decreased plasma antidiuretic hormone (ADH). These results demonstrate that afternoon injections of melatonin can alter renal function, which may involve direct (i.e., on ADH secretion and/or thirst mechanisms) or indirect (i.e., behavioral) effects.

A day/night rhythm of vasopressin and oxytocin in rat retina, pineal and harderian gland

Arginine vasopressin (AVP), oxytocin (OT) and neurophysins (Np) have been found in the pineal gland and the retina of the rat. Because the retina, pineal gland and Harderian gland (HG) serve analogous functions, we undertook a study to determine the presence of these peptides in these three organs of rats. They were detected by two specific methods: HPLC and specific radioimmunoassays. For Np, total neurophysins (NpT) were measured. To determine a 24 hr rhythm, the animals were maintained under a light/dark cycle of 12 hr/12 hr for 3 weeks. The pineal glands, retinae and HG were collected. Day/night rhythms of AVP, OT and NpT were demonstrated in the retina and HG; but the pineal gland had only AVP rhythm. A significant decrease in the rhythms at 4 a.m. was demonstrated in the retina and HG. The 24 hr variation of AVP in the retina seemed parallel to that of the HG.

Distribution in the macaque pineal of nerve fibers containing immunoreactive substance P, vasopressin, oxytocin, and neurophysins

The distribution of nerve fibers containing immunoreactive substance P (SP), estrogen-stimulated neurophysin (ESN), nicotine-stimulated neurophysin (NSN), oxytocin (OT), and vasopressin (VP) was examined in the epithalamic area of adult male and female macaques. Perfused or immersion-fixed epithalamic tissues, sectioned, and mounted on glass slides were processed through the avidin-biotin immunofluorescence method. Fibers containing immunoreactive SP were observed in the pineal organ along the periphery, in the perivascular space, and dispersed between the pinealocytes. Fibers were often observed in the pineal stalk region, and the habenular nuclei had high concentration of immunoreactive SP. Immunoreactive ESN fibers were observed in the stria medullaris, in the lateral habenula, in the pineal stalk, and in the pineal organ. Within the pineal, fibers containing ESN were present in the perivascular space, often concentrated in the walls of blood vessels, but also dispersed between pineal cells. Fibers containing OT, NSN, and VP were also present in the macaque pineal, but in lower quantities compared with fibers containing ESN. These studies show that the pineal of subhuman primates contain nerve fibers (ESN, NSN, VP, OT) of possibly hypothalamic origin. It also has a rich supply of SP fibers, which might be of habenula origin, peripheral parasympathetic ganglia origin, or both. The functional significance of these peptidergic nerve fibers remains to be determined. However, there are indications that they might be involved in regulation of blood flow and release of secretory products from the pinealocytes.

The pineal gland: anatomy, physiology, and clinical significance

Since the discovery of melatonin approximately 25 years ago, there has been intense study regarding the details of the structure and function of the pineal gland. This work is reviewed, with particular emphasis on those aspects of importance to human physiology and disease.

Arginine vasotocin in ovine fetal blood, urine, and amniotic fluid

Arginine vasotocin ([8-arginine]-oxytocin) (AVT), the primary antidiuretic principle in submammalian vertebrates, has been reported to be present in mammalian pituitary and pineal glands. Although the most phyletically ubiquitous of the known neurohypophysial peptides, AVT is still not recognized as a mammalian hormone. We examined plasma, urine, and amniotic fluid from fetal lambs by radioimmunoassay (RIA) for evidence of AVT to assess the possibility of its being such a hormone. Measureable quantities of AVT-like immunoreactivity (irAVT) were observed in fetal plasma (2.4 +/- 0.2 pg/ml), urine (1.4 +/- 0.2 pg/ml), and amniotic fluid (1.9 +/- 0.2 pg/ml). Since the AVT antiserum shows minimal cross-reactivity with arginine vasopressin (AVP) and oxytocin (OT), measurements of AVP and OT concentrations in the same biological fluids also were conducted with specific antisera. The results suggest that the irAVT was not accountable on the basis of cross-reaction. To further verify the identity of the irAVT, a high pressure liquid chromatography system using RIA as a means of detection was developed. This system is sufficiently sensitive to allow the separation and quantitation of picogram quantities of the synthetic peptides AVT, AVP, and OT. In this system, the irAVT in fetal plasma, urine, and amniotic fluid appeared as a single peak coeluting with synthetic AVT. These results indicate that AVT is present in ovine fetal plasma and support the view that the fetus secretes this peptide. The physiological significance of circulating AVT remains to be defined.

Secretion of neurophysins by the ovary in sheep

Measurements of venoarterial concentration differences across the ovary in anesthetized sheep have demonstrated that the ovary secretes ovine neurophysin I/II (oNP I/II) and that this process is stimulated by the prostaglandin F2 alpha analogue, cloprostenol. A parallel increase in the secretion of oxytocin (OT) was observed in response to cloprostenol, and the mean molar ratio of oNP I/II to OT secreted was 1.2. There was no detectable ovarian secretion of oNP III. Secretion of oNP I/II and OT was absent after hysterectomy. The data support other evidence indicating that the corpus luteum synthesizes OT, and confirm that the neurophysin associated with OT in the sheep is oNP I/II.

Presence of vasopressin, oxytocin and neurophysin in the retina of mammals, effect of light and darkness, comparison with the neuropeptide content of the neurohypophysis and the pineal gland

Arginine vasopressin (AVP) and oxytocin (OT) as well as their CNS carrier neurophysins (Np) have been found in the pineal gland. In view of the analogy between the pineal gland and the retina, the contents of these neuropeptides in rat, human and bovine retinae were determined. AVP, OT and Np were detected by specific radioimmunoassay (RIA) and their presence confirmed by RIA measurements (1) in rat and human retinae on HPLC fractions and (2) by the detection of the C-terminal portion of the precursor to AVP and its associated Np = propressophysin (CPP). The AVP and OT content in the retina of the rat was modified by light: AVP and OT content was smaller at 2 a.m. than at 2 p.m., but was increased by a 7 day constant exposure to darkness. In contrast, pituitary content was decreased after 7 days of constant darkness. If one optic nerve was cut we observed a decrease in retinal AVP content compared to the contralateral side and a decrease in pituitary AVP content. Our data clearly demonstrated the presence of AVP, OT and Np in the retina and their variation induced by light. It is probable that these peptides are of central origin.