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A. HOWE and A. J. THODY

SUMMARY

The changes in the content of melanocyte-stimulating hormone (MSH) and histology of the neuro-intermediate (n.i.) lobe were followed in rats which drank 2% sodium chloride for periods from 1–15 days.

The pars intermedia showed a biphasic response. During the initial phase of 1–4 days there was a rapid rise in the MSH content, by 153% in the first day, falling back to control level by 4 days. These fluctuations were paralleled by an increase in the normally small numbers of Type 2 cells and at the same time numerous Type I cells showed hypertrophy and degranulation.

After 4 days on saline there was a second rise in the MSH content, which was still evident at 15 days; during this second period the number of Type 2 cells declined to normal levels. The degranulated Type 1 cells also disappeared, most of Type 1 being smaller in size and intensely PAS-positive.

After the ingestion of saline it apparently takes several days before the pars intermedia adapts to a new level of activity.

The likely significance of these changes and the possibility of a relationship between the pars intermedia and the neurohypophysis are discussed.

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A. HOWE and A. J. THODY

SUMMARY

The adenohypophysis of the pig was examined histochemically for the presence of 11 oxidative enzymes, namely: 1.1.1.27 l-lactate: NAD oxidoreductase, 1.1.1.30 d-3-hydroxybutyrate: NAD oxidoreductase, 1.1.1.37 l-malate: NAD oxidoreductase, 1.1.1.41 threo-d s-isocitrate: NAD oxidoreductase (decarboxylating), 1.1.1.42 threo-d s-isocitrate: NADP oxidoreductase (decarboxylating), 1.1.1.49 d-glucose-6-phosphate: NADP oxidoreductase, 1.1.99.5 l-glycerol-3-phosphate: (acceptor) oxidoreductase, 1.3.99.1 succinate: (acceptor) oxidoreductase, 1.4.1.2 l-glutamate: NAD oxidoreductase (deaminating), 1.6.99.1 reduced-NADP: (acceptor) oxidoreductase, 1.6.99.3 reduced-NAD: (acceptor) oxidoreductase.

With the exception of 1.1.1.30 d-3-hydroxybutyrate: NAD oxidoreductase, activity was found throughout the adenohypophysis for all these enzymes. A comparison was made with the activity for these enzymes in liver.

In the adenohypophysis, the pars tuberalis exhibited the highest activity for all enzymes, generally equal to or greater than that shown by the liver. The pars intermedia and the pars anterior showed similar activity for these enzymes, in general of a lower order than that given by the liver. The pattern of enzyme distribution in the pars intermedia is described; high activity for 1.1.1.37 l-malate: NAD oxidoreductase, 1.1.1.27 l-lactate: NAD oxidoreductase, 1.6.99.3 reduced-NAD: (acceptor) oxidoreductase, 1.6.99.1 reduced-NADP: (acceptor) oxidoreductase was shown by cells lining cysts and the pituitary cleft.

The findings are discussed in relation to the possible association of these enzymes with secretory function.

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A. J. THODY and S. SHUSTER

The anterior pituitary has an important role in the control of sebaceous gland activity. This effect is mediated in part by thyrotrophic hormone (TSH) and adrenocorticotrophic hormone (ACTH) through their actions on the thyroid and adrenal glands respectively (Thody & Shuster, 1970a, 1971, 1972a). Ablation and replacement experiments suggest that the gonads also have a major influence (Thody & Shuster, 1970a, b), but although there is evidence that gonadotrophins will stimulate sebaceous glands in the human male (Strauss & Pochi, 1963) no data are available from experimental animals. We therefore decided to examine the effect of gonadotrophins on sebum secretion in the rat.

Male Wistar rats were hypophysectomized when 8–9 weeks old and 4 weeks later received either 0·9 units human menopausal gonadotrophin (Humegon)/day or no treatment. Humegon was dissolved in 0·9% NaCl solution and subcutaneous injections were given daily for a period of 2 weeks. At

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A. J. THODY and S. SHUSTER

SUMMARY

Thyroidectomy of intact and castrated rats produced significant reductions in their rates of sebum secretion. Replacement therapy with thyroxine (T4) increased the rate of sebum secretion of the castrated-thyroidectomized rats. Treatment with testosterone propionate also stimulated sebum secretion in castrated-thyroidectomized rats. When given together these two hormones had an additive effect on the rate of sebum secretion.

Thyrotrophic hormone (TSH) stimulated sebum secretion in castrated-hypophysectomized, but not in thyroidectomized rats.

It is concluded that TSH affects sebum secretion through its action on the thyroid, presumably by stimulation of T4 secretion.

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A. J. THODY and S. SHUSTER

It is generally believed that the activity of the sebaceous glands depends to a large extent on the gonads. The pituitary also appears to be involved in the physiology of these glands (Ebling, Ebling & Skinner, 1969; Nikkari & Valavaara, 1969; Thody & Shuster, 1970). The relationship between the pituitary and the sebaceous glands may be exerted via growth hormone and prolactin for Ebling et al. (1969) have shown that these pituitary hormones facilitate the effect of testosterone on sebum secretion. This present study was carried out to see whether the pituitary influence on sebum secretion is also mediated through the thyroid and adrenal glands.

The rate of sebum secretion was measured (Archibald & Shuster, 1969) in 12- to 15-week-old rats which had received one of the following treatments: castration, castration and adrenalectomy, castration and thyroidectomy, castration and hypophysectomy, or no treatment (intact controls). Castration was carried out when the

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A. J. THODY and S. SHUSTER

Department of Dermatology, University of Newcastle upon Tyne, Newcastle upon Tyne, NE1 4LP

(Received 15 October 1976)

In 1972 we suggested that α-melanocyte-stimulating hormone (α-MSH) had a physiological role as a sebotrophic hormone in the rat (Thody & Shuster, 1972) and it now appears that α-MSH is the previously suspected but unidentified sebotrophic hormone (Thody & Shuster, 1973; Shuster & Thody, 1974).

Since previous studies have mainly been concerned with exogenous MSH we examined the effect on sebum secretion of changes in endogenous MSH secretion induced by drugs.

Adult Wistar rats were housed in a light and temperature-controlled room and maintained on tap water and Oxoid breeding diet. The following treatments were carried out for 2 weeks after which time sebum secretion was measured by the method of Archibald & Shuster (1970). (i) Trifluoperazine (Smith, Kline & French) (0·5 mg/day) was administered intraperitoneally in 0·9% saline to male rats twice

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A. J. THODY and S. SHUSTER

Removal of the pituitary gland from the rat produces a decrease in the rate of sebum secretion (Nikkari & Valavaara, 1969; Ebling, Ebling & Skinner, 1969; Thody & Shuster, 1970 a). However, it is not established which pituitary hormones are involved in the control of sebaceous gland activity. In this study we have examined the effect of a new pituitary hormone, β-lipotrophin (β-LPH) (Birk, & Li, 1964; Li, 1968), on the rate of sebum secretion in the rat.

Female Wistar rats were ovariectomized when 5–6 weeks old and hypophysectomized at 7–8 weeks of age. Two weeks later the rats were divided into two groups and received either no hormone treatment (controls) or 0·1 mg β-LPH/day. The injections were given subcutaneously and continued for 2 weeks. At the end of this time the rate of sebum secretion was measured by the method of Archibald & Shuster (1970).

In this method the

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A. J. THODY and S. SHUSTER

SUMMARY

Testosterone propionate (TP) was administered to female rats at 3 and 6 days of age. When adult the sebum secretion rate of these rats was significantly increased, although the response to TP was normal.

Neonatal androgen treatment had no effect on the preputial gland weight of adult female rats. On the other hand ovarian weight was reduced.

After ovariectomy of normal adult rats there was an increase in sebum secretion to a level comparable to that found in adult rats given TP as neonates. By contrast there was no change in sebum secretion after ovariectomy of adult rats given TP as neonates and the rate of sebum secretion in these rats was comparable to that in ovariectomized normal adults.

It is suggested that after neonatal androgen treatment the normal inhibition of the sebaceous glands by the ovaries was abolished and consequently the rate of secretion was increased. Thus the endocrine state in early life may have a lasting effect on sebaceous gland activity in the adult.

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A. J. THODY and S. SHUSTER

SUMMARY

Adult male rats which had been castrated prepuberally secreted less sebum than intact rats. When hypophysectomy followed castration there was a further decrease in sebum secretion. Treatment of the castrated and hypophysectomized castrated rats with testosterone propionate produced a large and comparable increase in the sebum secretion of both groups. Testosterone propionate also caused a marked increase in the preputial gland weight of the castrated rats, although a much smaller response occurred after hypophysectomy. The effect of hypophysectomy on the response of the sebaceous and preputial glands to testosterone is discussed.

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A. J. THODY and H. DIJKSTRA

Sexually experienced male rats were used to test for whole body and preputial gland odours of female rats. The male rats clearly preferred whole body odours of intact female rats to those of preputialectomized female rats. The male rats also preferred the odour of preputial gland tissue of intact female rats to that of ovariectomized female rats and were especially attracted to the preputial gland odours of female rats in pro-oestrus and oestrus. The preputial gland odours of ovariectomized rats that had received oestradiol benzoate for 7 days were attractive to male rats, although similar treatment with progesterone was ineffective. However, a single injection of progesterone given 72 h after a single injection of oestradiol benzoate not only made ovariectomized rats receptive, but also made their preputial gland odours attractive to male rats.

The results suggest that the preputial gland of the female rat is responsible for odours that serve to attract sexually experienced male rats. Ovarian steroids, as well as controlling receptivity in the female rat, would also appear to control the production of sex attractants in the preputial gland. There was no relationship between the size of the preputial glands and their ability to attract male rats which suggests that preputial gland growth and production of sex attractants are not under the same hormonal control.