Changes in serum prolactin following binding and constant light exposure.

The effects of blinding and constant light exposure for 5 weeks on serum concentrations of prolactin were studied in male rats. Neither treatment had any effect on body, pineal, pituitary, testis, or seminal vesicle weights. Serum prolactin was not significantly altered by constant light exposure, but was significantly elevated by blinding. These data provide further support that prolactin secretion is elevated by blinding. It is suggested that prolactin may be partially responsible for the lack of significant gonadal atrophy following blinding in male rats.

Inhibitory properties of a bovine pineal tripeptide, threonylseryllysine, on serum follicle-stimulating hormone.

Administration of the bovine pineal peptide threonylseryllysine (TSL) to unilaterally ovariectomized (UO) mice as a single intraperitoneal injection on the day of UO reduced the 5-day compensatory ovarian hypertrophy. The same dose of TSL (175 ng/animal) significantly (p less than 0.01) reduced serum follicle stimulating hormone (FSH) in UO mice 24 h after surgery and administration of the peptide. In other experiments, adult male rats were anesthetized with urethane and given an intravenous injection of luteinizing hormone releasing hormone (LRH) followed by TSL in doses ranging from 1.5 to 1,500 ng/animal. TSL significantly delayed (p less than 0.05) the 15- and 30-min surge of serum FSH observed in control animals after 120 or 180 min in 3 of the 4 doses used (1.5, 15 and 1,500 ng/animal). In the animals receiving 150 ng TSL the LRH-induced FSH surge was delayed (p less than 0.05) until 30 min. The results indicate that the pineal tripeptide may inhibit or modify FSH secretion in the mouse and rat.

Isolation, purification and amino acid sequence of a tripeptide from bovine pineal tissue displaying antigonadotropic properties.

Studies were performed to isolate peptides displaying antigonadotropic properties from bovine pineal tissue. Inhibition of compensatory ovarian hypertrophy in adult mice was used as an index of activity to guide the purification of a bovine pineal extract in order to isolate these antigonadal peptides. Defatted bovine pineal glands were extracted with acetic acid and further purified by cation-exchange chromatography, gel filtration and paper electrophoresis. The electrophoretogram revealed sixteen ninhydrin spots, of which four were antigonadotropic. One of these fractions was subjected to paper chromatography which yielded two antigonadal fractions. Amino acid analysis of each of these fractions indicated that one was in pure form and the sequence was found to be threonylserinyllysine. The other fraction was heterogeneous, but contained no lysine. Analysis of the amino acid content of the other antigonadal fractions obtained after electrophoresis indicated the possibility that other peptides were present, but did not suggest the presence of arginine vasotocin.

Neurotransmitter regulation of arginine vasotocin release from rat pineal glands in vitro.

Studies were performed to determine the effects of neurotransmitters on arginine vasotocin (AVT) release in vitro. Rat pineal glands were incubated with 10(-8)M or 10(-6)M norepinephrine (NE), dopamine (DA), serotonin (5HT), and acetylcholine (ACH) for eight h after which the concentrations of AVT in the media were determined by radioimmunoassay. With the exception of ACH, none of the neurotransmitters had a significant effect on AVT release. ACH significantly (P less than 0.05) elevated AVT release in vitro at the 10(-6)M concentration but not at the 10(-8)M concentration. The data indicate that ACH may play a role in the regulation of rat pineal gland secretion of AVT in vitro.

Interaction of arginine vasotocin and norepinephrine upon pineal indoleamine synthesis in vitro.

The interaction of arginine vasotocin (AVT) and norepinephrine (NE) upon pineal gland indoleamine synthesis was investigated. Rat pineal glands were incubated for 10 h in Krebs--Ringer bicarbonate plus 2 mg/ml glucose, 1 mg/ml bovine serum albumin, [14C]tryptophan, NE (10(-6) M), and log doses of AVT ranging from 100 ng to 10 microgram. Incubation media were extracted for [14C]serotonin while the other [14C]indoleamines, melatonin, hydroxyindoleacetic acid (HIAA), methoxyindoleacetic acid (MIAA), N-acetylserotonin (NAS), hydroxytryptophol (HTOL), and methoxytryptophol (MTOH) were separated by thin-layer chromatography. Serotonin metabolism was decreased by 0.1 microgram AVT and NAS decreased by 1.0 microgram AVT. Melatonin synthesis was decreased by both 0.1 and 1.0 microgram AVT. AVT also decreased the conversion of [14C]serotonin to MIAA and to HTOL. The data indicates that AVT decreased NE-stimulated pineal indoleamine synthesis in vitro and further suggests that AVT may participate in the intracellular regulation of melatonin synthesis.

Antifertility properties of bovine pineal extracts: reduction of ovulation and pre-ovulatory luteinizing hormone in the rat.

Bovine pineal glands were extracted with acetic acid and partially purified on Sephadex G-25. Three fractions, F3, F4 and F5, were each administered to cycling female rats for 4, 2 or 1 day prior to ovulation to determine their effects on fertility, ovulation and the pro-oestrous surge of luteinizing hormone (LH). The incidence of pregnancy and the mean number of foetuses were reduced in animals after treatment with F3 or F4 but not in those treated with F5. Each of the F3 and F4 fractions significantly reduced the mean number of ova shed and the pre-ovulatory concentration of serum LH. The F5 fraction caused a moderate reduction of the pro-oestrous rise of serum LY but had no significant effect on ovulation. The data suggest that fertility in rats can be reduced by more than one substance of low molecular weight present in bovine pineal extracts through a modifying effect on LH secretion and subsequent ovulation.

Reduction of serum LH and testosterone in male rats by a partially purified bovine pineal extract.

PIP: The reduction of serum luteinizing hormone (LH) and testosterone in male rats by a partially purified bovine pineal extract is reported. Defatted bovine pineal glands were extracted with acetic acid and further purified on Sephadex G-25 to yield 3 antigonadotropic fractions designated at F3, F4, and F5. Each fraction was administered to young mature male rats at either 5 or 10 gm eq (equivalent to starting wet weight of tissue) dose levels daily for 5 days. The animals were necropsied 24 hours after the last injection. None of the fractions had an effect on accessory gland weight, however 5 or 10 gm eq of F4 significantly reduced testicular weight (p less than .025 and p less than .05, respectively) and 10 g eq of F4 and F5 significantly reduced anterior pituitary weight (p less than .05 and p less than .01, respectively). Serum LH was significantly lowered (p less than .05) by 10 gm eq of either F3, F4, or F5. Serum testosterone was reduced significantly only in those receiving 5 gm eq (p less than .05) or 10 gm eq (p less than .01) of F4. These data provide furhter evidence that some substances other than melatonin in bovine pineal are antigonadotropic.^ieng