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Summary.Six heifers with normal oestrous cycles were treated i.m. with 100 i.u. oxytocin on 3 consecutive days, commencing on Days 1–6 after oestrus, and the levels of prostaglandin (PG) F in posterior vena cava plasma were compared with pretreatment values. An increase of PGF in response to oxytocin was significantly influenced by day, with the greatest response occurring on Day 3 after oestrus. In an ovariectomized heifer the levels of PGF in posterior vena cava plasma increased 24 h after priming with oestradiol, but no further increase occurred after oxytocin injection. Peak levels of PGF were higher in the plasma of the posterior vena cava than in the jugular vein. Various storage conditions of the blood before centrifugation and freezing (−20°C) produced significant differences in plasma levels of endogenous PGF, but storage experiments with added labelled PGF-2α indicated that the PG was stable in plasma and whole blood.

In mammals suffering from vitamin A deficiency, the testes show various degrees of atrophy associated with a reduction in spermatogenic activity (Moustgaard, 1969). Coward, Howell, Pitt & Thompson (1966) and Palludan (1966a) demonstrated that this effect of vitamin A deficiency is not related to an endocrine deficiency, and Palludan (1966b) in the boar and Ahluwalia & Bieri (1971) in the rat showed that it is due to a direct effect on the process of spermatogenesis. The same investigators observed that in animals whose rate of growth and health were maintained on retinoic acid (vitamin A acid), testicular lesions still occurred. Injections of retinol (vitamin A alcohol), or retinaldehyde (vitamin A aldehyde) made directly into the testes restored spermatogenesis at the site of injection. Little information is available on the levels of endogenous vitamin A in testis

Summary.Prepubertally castrated boars received subcutaneous injections twice weekly, from 13 to 35 weeks of age, of dehydroepiandrosterone (2 mg/5 kg) or oestrone (1 mg/5 kg). Dehydroepiandrosterone did not support the growth and secretory activity of the accessory organs, or induce copulatory behaviour. However, oestrone caused hypertrophy of the prostate, seminal vesicles and bulbourethral glands which was due to an increase in fibrous stromal tissue and not to the secretory epithelium. Oestrone also induced some male mating behaviour patterns in the presence of an oestrous gilt, although penile extrusion and ejaculation did not occur. The morphological and behavioural effects of the steroid treatments were supported by steroid profiles in blood plasma as seen in comparison with androgen and oestrogen values of intact and untreated castrated boars. It is concluded that oestrogen in the intact boar might enhance the secretion of the accessory organs by affecting the neural control of the secretory processes rather than by increasing the amount of secretory epithelium in the glands.

Summary.Bilateral olfactory bulbectomy was carried out on 16 post-pubertal gilts during the winter and spring of 2 consecutive years. Eight bulbectomized gilts in Exp. 1 had 2–7 regular periods of oestrus before becoming anoestrous for > 100 days in the summer and autumn. During November, 3 of these gilts were placed with a boar and became oestrous within 9 days, were mated and established normal pregnancies; the remaining pigs also resumed normal oestrous cycles when transferred to other pens. The following year anoestrus again occurred during the summer in gilts and in sows after weaning. In Exp. 2, 8 bulbectomized gilts remained in the same pens throughout the experiment, 4 were housed with a vasectomized boar and 4 away from boars. As in Exp. 1, the same periods of anoestrus occurred throughout the year, whereas 4 unoperated pigs housed nearby had continuous oestrous cycles.Ovulation without oestrus occurred in some bulbectomized pigs even after gonadotrophin treatment. Prolonged anoestrus in Exp. 1 was associated with nonovulatory levels of plasma oestrogen and low plasma progesterone and LH values. Behavioural, morphological and endocrine data indicate that the effects of bulbectomy on oestrous cycles in post-pubertal gilts are mediated at the hypothalamus. The seasonality of the effects seems likely to be due to bulbectomy unmasking a photoperiodic influence.

Summary.Three groups of 5 prepubertally castrated boars received twice weekly subcutaneous injections from 16 to 28 weeks of age of 5α-dihydrotestosterone propionate (1 mg/kg), oestradiol-17β dipropionate (0·1 mg/kg), or a combination of the two steroids. The pigs were tested each week for sexual behaviour with an oestrogen-treated ovariectomized gilt. 5α-Dihydrotestosterone did not induce copulatory behaviour whereas oestradiol initiated mounting, although this behaviour was not maintained. However, the combined hormonal treatment induced the full pattern of copulation, including ejaculation, in 4/5 pigs. Oestrogen-treated animals also showed champing and salivation. None of the pigs treated with 5α-dihydrotestosterone showed lordosis when exposed to a mature boar. Increases in the size of the penis, the ischioand bulbocavernosus muscles, seminal vesicles and bulbourethral glands were produced by 5α-dihydrotestosterone, and, with the exception of the penis, this hypertrophy was further enhanced by additional treatment with oestradiol. Increases in the weight of the prostate and muscular urethra were due mainly to the effects of oestrogen; this steroid caused extensive development of fibromuscular tissue and also increased mammary teat length. In the submaxillary salivary glands, synergism between 5α-dihydrotestosterone and oestradiol resulted in hypertrophy of the serous cells.

Summary.The pheromone binding protein 'pheromaxein' which binds the pheromonal 16-androstene steroids in the saliva of the male pig (boar), was degraded and lost its binding activity in saliva incubated in air for 72 h at 21°C and 37°C. However, pheromaxein and its binding activity were retained in saliva incubated for 168 h at 4°C. When the 3H-labelled pheromones 5α-androst-16-en-3α-ol (3α-androstenol), 5α-androst-16-en-3-one (5α-androstenone) and 5α-androst-16-en-3β-ol (3β-androstenol) were incubated with boar saliva for 168 h at 21°C, 3α-androstenol was primarily converted to 5α-androstenone and 5α-androstenone to 3β-adrostenol; 3β-androstenol was unchanged. Evidence was obtained for microorganisms being responsible for these steroid transformations.

Summary.Day-6 rabbit blastocysts were incubated with 3H-labelled neutral steroids. Pregnenolone metabolism was insignificant, but progesterone was extensively metabolized to 5β-pregnanedione (5β-pregnane-3,20-dione) and 5β-pregnanolone (5β-pregnan-3β-ol-20-one). Some dehydroepiandrosterone (DHA) was converted to 5-androstene-3β,17β-diol; androstenedione and testosterone were interconverted, and both 4-ene steroids were metabolized to 5α-reduced compounds. There was no evidence for oestrogen synthesis from progesterone or androgens. Exogenous cofactors had no significant effect on the course of steroid metabolism. Oestradiol and oestrone were determined in blastocysts, and high levels of oestrogen were found in blastocysts from superovulating rabbits. Injection of [3H]oestradiol into pregnant rabbits gave rise to radioactivity associated primarily with oestradiol in uterine tissue, uterine flushings and blastocysts.It is concluded (1) that the capacity of the Day-6 rabbit blastocyst to metabolize progesterone and androgen may be utilized in vivoto protect the blastocyst from excess maternal progesterone, and to involve androgens in an anabolic role, and (2) that blastocyst oestrogen may be partly of maternal origin.

Summary.Prepubertally castrated boars received subcutaneous injections twice weekly, from 12 to 38 weeks of age, of testosterone or 5-androstenediol (5-androstene-3β,17β-diol) (2 mg/5 kg), or each of these steroids in combination with oestrone (1 mg/5 kg). All steroid treatments induced growth and secretory activity of the accessory organs. The prostate was maintained best by testosterone, and the seminal vesicles by 5-androstenediol. No specific effects of oestrone on these organs were found. Champing of excess saliva was induced in all treated pigs when they were introduced to an oestrous gilt, but only boars receiving testosterone displayed intense mating behaviour including mounting and, in 3 animals, ejaculation; no specific effects of oestrone on behaviour were seen. Low normal levels of unconjugated androgen, and normal to high levels of unconjugated oestrogen were circulating in the treated pigs. There was evidence that peripheral metabolism of exogenous steroids had occurred: 5-androstenediol to testosterone, these two androgens to oestrogen, and sulphation of oestrogen. The sulphate conjugates of dehydroepiandrosterone, 5-androstenediol and oestrone predominated in the peripheral plasma of mature intact boars. Concentrations of 3α-androstenol (5α-androst-16-en-3α-ol) in the submaxillary glands of androgen-treated pigs were similar to those in untreated castrates, thus indicating that androgens are probably not precursors of the pheromonal 16-androstene steroids in vivo.

Summary.Bilateral olfactory bulb ablation was carried out surgically on 8 prepubertal Large White boars when they were 10–12 weeks of age. Between 26 weeks and slaughter at 47–49 weeks of age, androgen was determined in peripheral blood plasma of bulbectomized and unoperated control animals. The pigs were exposed to oestrous female pigs to observe mating behaviour, and to alien boars to observe aggressive behaviour. Saliva produced during behaviour tests was extracted with diethyl ether and levels of the pheromonal 16-androstene steroids in the extracts were determined by a colorimetric assay. After slaughter the testes, accessory organs and submaxillary glands were weighed, and pieces of tissue together with olfactory epithelium were processed for light microscopy; fructose and zinc were determined in the seminal vesicles. The results showed that, contrary to findings in some rodents, prepubertal bilateral bulbectomy in the male pig had no significant effect on mating or aggressive behaviour, or testicular function in so far as complete spermatogenesis was present and normal levels of androgen and pheromone were maintained together with the integrity of the accessory organs. However, in keeping with findings in other species, the height of the olfactory epithelium was generally reduced in the bulbectomized pigs.

Five true hermaphrodite pigs and two male pseudohermaphrodite pigs were studied. A 38XX sex chromosome constitution was found in peripheral leucocytes of three true hermaphrodites and in one male pseudohermaphrodite; XX/XY mixoploidy was present in the leucocytes of the remaining male pseudohermaphrodite. The occurrence of C19steroids, including 16-androstenes, in the testicular tissue and submaxillary gland of intersex pigs was of a similar pattern to that found previously in mature boars, and masculinization of the genital tract was related to the amount of testicular tissue present. It is postulated that in the absence of germ cells in the testicular tissue of intersex pigs the Sertoli cells may be involved in the metabolism of dehydroepiandrosterone to 5-androstenediol, a possible testosterone precursor in the pig. The high levels of 16-androstenes found in the submaxillary gland of intersex pigs indicates that these steroids are responsible for `boar taint' in these animals. In contrast to the boar, no consistent relationship was found between the occurrence of C19steroids and the degree of masculinization of the submaxillary gland; it is postulated that the predominantly female genetic constitution may have affected the response of the salivary gland to androgen.

After extraction from the testes of boars of different ages, C19steroids including 16-androstenes were determined by gas-liquid chromatography. Similarly, 16-androstenes were determined in the submaxillary glands of these boars. A high concentration of testosterone was found in the testes of 84-day-old fetuses, and this might be significant in the differentiation of male behaviour. The amount of testosterone exceeded that of androstenedione during postnatal development, and dehydroepiandrosterone and 5-androstenediol as free and sulphates were found in high concentrations particularly in postpubertal boars, suggesting that the 5-ene pathway for the synthesis of testosterone might be important. There was a change in the predominance of individual 16-androstenes in the testis during development, which closely paralleled the sequence for the biosynthesis of these compounds proposed from previous studies in vitro.Whereas the amount of 5α-androst-16-en-3β-ol exceeded that of 5α-androst-16-en-3α-ol in postpubertal testes, 5α-androst-16-en-3α-ol was predominant in the submaxillary glands at all ages. The high concentration of 16-androstenes found in the mature boar, are discussed in relation to their release as pheromones and as factors responsible for taint in boar meat.

The growth of the pituitary and of the reproductive tract of Suffolk rams from birth to 168 days of age has been studied. Pituitary icshand fshconcentrations were determined by bio-assay. The pattern of testicular androgen production has been examined using chemical and histological techniques and the relationship to spermatogenesis studied. Pituitary gonadotrophin content increased sharply from 42 days of age but was only weakly correlated with other parameters measured. The androstenedione : testosterone ratio was at its narrowest at birth; however, testosterone was the predominant androgen from birth onwards. Androgen concentration fluctuated but the total content increased with increase in testicular weight. Fructose was present in the seminal vesicles from birth and citric acid from 14 days; citric acid concentration was about one-tenth that of fructose. There was a significant correlation between testicular androgen content and the fructose and citric acid concentration and content of the seminal vesicles. Seminiferous tubule diameter was significantly correlated with most of the parameters measured. Testicular weight increased sharply from 42 days of age. Androgen production was present at birth and preceded spermatogenesis which began when testis weight exceeded 10 g, which was after 56 days of age. Spermatozoa were present in the seminiferous tubules at 112 days of age.

A biochemical sexual dimorphism exists in the submaxillary gland of the pig. Patterson (1968) identified 5α-androst-16-en-3α-ol and 5α-androst-16-en-3-one in the submaxillary gland of boars but found none in the female pig. Booth (1972) isolated testosterone and 5α-dihydrotestosterone from the submaxillary glands of boars only. These observations suggest that the submaxillary gland of the boar, like that of the male mouse (Berkman & Kronman, 1970), may be a target organ for androgen. In the mouse, hypertrophy of the granular serous tubules in the submaxillary gland is known to occur under the influence of androgen (Berkman & Kronman, 1970) and the possibility that a similar situation might exist in the pig was therefore examined. In addition, the activity of Δ5-3 β-hydroxysteroid dehydrogenase in the gland was studied histochemically.Submaxillary glands were removed from nineteen Large White X Essex pigs of different ages, and weighed within 30 min of slaughter (see