Progesterone, estrogen 및 ortho-novum의 투여로 인한 뇌하수체 및 난소의 형태학적 변화
Morphologic alterations of anterior hypophysis and ovaries of rats induced by progesterone, estrogen and ortho-novum
Population control is an eminent world-wide problem, and various contraceptive measures are being sought to meeting this problem. It is becoming clear that the oral contraceptives will be a choice of method among various contraceptive means.
Currently used oral contraceptives are composed of synthetic progesterone (progestins) and estrogens. The rationale behind the use of these sex hormones for contraception derived from the suggestion of Beard(1897) who thought that corpus luteum of the pregnancy might inhibit ovulation during the course of pregnancy.
Subsequently Makepeace et al., (1937) demonstrated that an extract from the corpus luteum inhibited ovulation in the rabbit, and this effect was later confirmed by Astwood et al. (1939) in the rats, and Pincus et al. (1953) in rabbits. Austin et al. (1956) and Buchholz et al. (1964) found that estrogen also has antiovulatory effect by depression of follicle stimulating and luteinizing hormones. These natural hormones are best effective by parenteral injections, but their anti-ovulatory effects are inconsistent by oral administration.
Colton in 1952 succeeded to synthesize very potent progestational agent, norethynodrel, and this agent was proved to have progestational, estrogenic, pituitary inhibiting, and antiovulatory effects by biological tests (Pincus et al.
1956). Subsequently several new synthetic progestational agents(progestins) developed (Drill 1966). All progestins showed good control of ovulation in successive cycles, but the incidence of spotting and break-through bleeding was high. Therefore, it has since been found necessary to add an estrogen to progestins
being evaluated as oral contraceptives in order to aid in the maintenance of the endometrium.
It has been farily well established in studies on animals and women that the oral contraceptives act to prevent ovulation by inhibiting the secretion of gonadotropins from the pituitary gland (Drill and Saunders 1964, Kupperman 1957). However, it is not clear which of gonadotropins is specially inhibited, and whether the inhibition is brought about by a decreased production or release of the gonadotropins. It is also very recent that characterization of seven different cells in anterior pituitary glands was established.
The present investigation is aimed to study ultrastructural changes of anterior pituitary following the administration of Ortho-Novum, an oral contraceptive, in comparison with the changes induced by progesterone or estrogen alone.
Materials and Methods
Female albino rats weighing around 205 gms were used for the experiments. They are divided into four groups and treated as followings.
Group Ⅰ: Normal control (25 animals)
Group Ⅱ: Progesterone treated
A: 3mg/kg/day (25 animals)
B: 15mg/kg/day (25 animals)
Group Ⅲ: Estrogen treated
A: 0.03mg/kg/day (25 animals)
B: 0.15mg/kg/day (25 animals)
Group Ⅳ: Ortho-Novum treated
A: 0.3mg/kg/day (25 animals)
B: 1.5mg/kg/day (25 animals)
Drugs are given by intramuscular injections at each thigh on alternate day for the period from 15 to 60 days. All animals were fed with commercial diet containing more than 15% of protein. Five animals from each group were killed at the 15th day, 10 animals each at the 30th and 60th days. Pituitaryk thyroid, adrenals and ovaries were removed at necropsy. They were weighed and examind for gross alteration. Then each organs were fixed in 10% neutral formalin. Microsections were made from paraffin block and all sections were stained by hematoxylin-eosin method. Sections of the pituitary glands were also stained by PAS reaction method and PAS orange G method to differentiated gonadotropes and thyrotropes. For electron microscopic examinations, pituitary glands from two to three animals in each group were cut in 1 cu. mm size and fixed in 1% osmium tetraoxide. Sections were cut with glass knife and stained with uranyl acetate and lead hydroxide. Ultrastructural examinations
were made with Hitachii 11 E electron microscope.
Results and Summary
A. Alteration of body weight:
Animals in normal control group showed gradual increase of body weight during the experimental period. Animals treated with progesterone showed enhanced increase of body weight in comparison to normal control animals. However, animals treated with either estrogen or Ortho-Novum showed gradual decrease of the body weight during the experimental period.
B. Changes of the weight of pituitary, thyroid, adrenals, and ovaries:
The weight of the pituitary expressed as gm/100 gms of body weight showed rapid increase following the estrogen treatment, but no significant change was noted following the treatment with either progesterone or Otho-Novum. Weight of the thyroid, adrenals and ovaries did not change notably in all experimental groups.
C. Light microscopic observations:
The most marked changes of anterior pituitary were observed in estrogen treated animals, which showed decrease of gonadotropes and hyperplasia of chromophobe cells. These changes became prominent as the dose and duration of the treatment increased. Similar changes were also noted in progesterone or Ortho-Noveum treated animals but to a lesser degree.
The ovaries showed very prominent changes in all of experimental groups. The changes in the ovaries consisted of degeneration and maturation arrest of the follicles as evidenced by karyorrhectic destruction of granulosa cells of medium or large sized follicles leading to the formation of thin walled cystic follicle with death of the ovum. These changes were most marked in estrogen treated animals and least in progesterone treated animals. The changes in corpus luteum consisted of lack of new corpus luteum formation, vacuolization and necrosis of preexisting corpus luteum. The lack of new corpus luteum was noted in all experimental groups while the vacuolization and necrosis of the pre-existing corpus luteum were noted only in the animals treated with progesterone.
Thyroid and adrenal glands showed no significant histologic alterations.
D. Electron microscopic observations:
Ultrastructural examinations of the anterior lobe of the pituitary glands showed changes in luteotropic hormone secreting cells, follicle stimulating hormone cells, and luteinizing hormone secreting cells. Lu teotropic hormone cells showed decreased granules with dilated endoplasmic reticulum and swelling of the mitochondria. Follicle stimulating hormone cells showed atrophy with decreased granules and poorly developed but dilated endoplasmic reticulum suggesting functional immaturity. The changes of luteinizing hormone cells were mild and characterized by decrease of secretory granules and increase of dens bodies. No significant changes in other types of cells were noted. These changes were observed in all of the experimental groups, but quantitatively most marked in the animals treated with estrogen.