Effects of ovariectomy, estrogen and pregnancy on mammalian hair color.

The effect of ovariectomy, estrogen and pregnancy on hair color has been studied in mature all red and all black guinea pigs. Hair samples were obtained from the scalp and anterior abdominal wall of each animal before and during the course of each experiment. Control samples of hair were also removed from the same areas of a group of untreated animals. The hairs were mounted on slides and hair color counts were performed. Subjective color comparisons between hair samples were also made. The results showed that ovariectomy, estrogen and pregnancy have no definite effect on hair color. This lack of response of the follicular melanocytes to the procedures in the present experiments is in marked contrast to the responses obtained previously with the epidermal melariocytes; the latter are inhibited by ovariectomy and strongly stimulated by estrogen and pregnancy. The significance of this independent activity of morphologically identical pigment cells is discussed. It is well known that the sex hormones can influence pigmentation of the skin. Recently it has been demonstrated that ovariectomy inhibits the process of melanogenesis in the skin, while estrogen stimulates it (1, 2). It is also known that during pregnancy skin pigmentation in certain areas of the body becomes greatly increased and it is believed that estrogen and progesterone, probably assisted by the melanocyte stimulating hormones of the pitui— tary, are responsible (3, 4, 5). Despite the morphological similarities between the melanocyte systems of the hair follicle and the epidermis, it is possible that the two cell groups respond differently to hormonal stimulation. Their independent action is clearly seen in the white haired Negro and the dark haired Caucasian. The object of the present work is to establish whether ovariectomy, estrogen and pregnancy can influence follicular melanocytes in the same mamier as they influence epidermal malanocytes. MATERIALS AND METHODS Thirty-three mature virgin female guinea pigs were used. They were either all red or all black in color but the animals were not genetically pure Received March 28, 1969; accepted for publication July 17, 1969. * From the Department of Anatomy, New Jersey College of Medicine and Dentistry, Jersey City, N. J. 07304. Present address: Department of Anatomy, Yale University, New Haven, Conn. strains. The guinea pigs were divided into three groups as follows: GROUP 1 (Control experiment) consisted of six all red and six all black animals. Hair samples were taken from the scalp and anterior abdominal wall of each animal by clipping. The hair was cut close to the skin with standard electric clippers. A group of undisturbed hairs from each clipping was mounted on a slide under a coverslip as described previously (6). Thereafter additional samples were removed from exactly the same areas at monthly intervals for 3 months. GROUP 2. (Ovariectomy and estrogen experiment) consisted of six all red and six all black animals. Hair samples were taken from the scalp and anterior abdominal wall of each animal as described above. Each animal was then ovariectomized. One month later a second sample of hair was removed from the same areas. The guinea pigs then each received intramuscularly once daily for a month 0.1 mgm. estradiol benzoate in ethyl oleate. At the end of the hormone treatment a third and final hair sample was taken from exactly the same areas noted above. GROUP 3. (Pregnancy experiment) consisted of six all red and three all black animals. At estrus, when the vaginal membrane disappeared, hair samples were taken from the scalp and anterior abdominal wall of each animal. Each animal was then placed in a cage with a male guinea pig for 48 hours. The male animal was then removed and the female left isolated for the remainder of the experiment. By this means it was possible to accurately date the onset of pregnancy. A second hair sample was taken from the same areas one month later. At six weeks, it was possible by abdominal palpation to determine whether the animal was pregnant. If fertilization had not taken place the animal was discarded and replaced. A third hair sample