ANTIFERTILITY PROPERTIES OF BOVINE PINEAL EXTRACTS: REDUCTION OF OVULATION AND PRE-OVULATORY LUTEINIZING HORMONE IN THE RAT

ABSTRACT 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 LH 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.

SOME ANTIGONADOTROPHIC EFFECTS OF MELATONIN-FREE BOVINE PINEAL EXTRACTS IN RATS

ABSTRACT Studies were made to determine if a substance other than melatonin was present in bovine pineal gland extracts which possessed properties inhibitory to some gonadotrophin-dependent reproductive parameters in rats. Bovine pineal extracts were partially purified by organic solvent extraction or by ultrafiltration and gel-filtration to exclude melatonin. When administered to rats, the extracts inhibited compensatory ovarian hypertrophy, delayed vaginal opening time and reduced the incidence of constant oestrus. Either of the melatonin-free extracts reduced significantly the concentration of serum luteinizing hormone (LH) in long-term castrate male rats. The data suggest that some substance other than melatonin present in bovine pineal glands has a modifying effect on the reproductive parameters observed probably due to its inhibitory effect on LH.

INTERACTIONS OF THE PINEAL AND EXPOSURE TO CONTINUOUS LIGHT ON ORGAN WEIGHTS OF FEMALE RATS

ABSTRACT Either exposure to constant light for 80 days or pinealectomy produced similar changes in the weights of the ovaries and adrenals of female rats. These were not additive when both procedures were employed. Pinealectomy did not share with light-exposure the capacity to induce uterine hypertrophy. Rats exposed to constant light for 56 days had lighter pineals than animals kept in darkness; this decrease was not affected by administration of bovine pineal extracts. The increase in ovarian weight produced in rats by exposure to light for 56 days was prevented by bovine pineal extracts, but these extracts were without effect on the uterine hypertrophy produced under the same conditions. These data suggest that the effect of light upon the weight of the ovary is mediated via the pineal.

The pineal gland and aldosterone

It has recently been suggested that the canine pineal gland secretes a hormone which stimulates the adrenal cortex to release aldosterone. The following experiments were undertaken to determine what effect pinealectomy or administration of bovine pineal extracts has on certain physiologic variables associated with aldosterone activity in rats: a) the relative size of the zona glomerulosa, compared with total adrenal area, was determined planimetrically in 25 female rats treated with pinealectomy, pineal extracts, or both; b) urinary potassium excretion was measured in 4 pinealectomized and 4 control female rats; c) the elective saline intakes, at concentrations ranging from 0 to 3.0%, were measured in 5 male control rats and in 5 animals given 1.0 ml/day of pineal extract. Pinealectomy or pineal extract had no effect on any of these variables, suggesting that the pineal gland does not regulate aldosterone secretion in the rat.