The effect of pineal extracts on hormone-induced rat uterine contractility.

Abstract

Crude pineal extracts are apparently capable of exerting both a stimulatory and an inhibitory effect on the reproductive system of laboratory animals. The two active influences were separated as far as possible by means of TCA extraction (Reiss, Davis, Sideman, Mauer & Plichta, 1963) and the general methods of preparing the various cattle pineal fractions, used in the present study, were described. The inhibitory activity was found mainly in the supernatant fluid while the precipitate contained a stimulatory substance. The present paper reports on the activity of a few of these pineal fractions on rat uterine contractility induced in vitro by acetylcholine, pitocin and serotonin. Melatonin inhibited serotonin-induced rat uterine contractions (Hertz-Eshel & Rahamimoff, 1965) as well as pitocin-induced uterine contractions of women and mice (Davis, McGowan & Uroskie, in preparation). Oxytocic activity was isolated from bovine pineal gland (Milcu, Pavel & Neacsu, 1963). The effect of pineal amines on various types of mammalian smooth muscle has received consideration (Wurtman, Axelrod & Kelly, 1968). Uteri from adult Sprague Dawley rats (250 g) were suspended in 30 ml aerated de Jalon solution at 29-5° C and a single uterine contraction was induced by administering either one of three standards : 2 μg acetylcholine, 10 mu pitocin or 2 μg ofserotonin. The pineal extract was given in combination with the standard between two standard-induced contractions. The freezedried bovine pineal powders used were: TCA extract (Dowex, pH 7-4) ; super¬ natant of the original boiled residue from a simple aqueous extract; aqueous supernatant in a dialysing bag. Study 1 (Text-fig. 1). Trichloroacetic acid extract (0-1, 0-5 or 1-0 mg) was injected into the muscle bath simultaneously with serotonin (2 μg) or pitocin (10 mu) and exposed to the uterine horn for 3 min. For comparison, serotonin