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1. Goitrogenic action of methallibure (ICI-33828) has been studied in mice gerbil and hedgehog using thyroid weight and histological structure as an index. Liquefaction and vacuolation of thyroid follicles were most prevelant after methallibure administration. 2. The I131 content of the thyroid gland was significantly higher in the methallibure treated groups than in the controls. This denotes a decrease in the rate of discharge of thyroid hormone. 3. Protein bound radioiodine (Pb I131) was low after methallibure administration. 4. Methallibure administration brings about hypertrophy of pituitary thyrotrophs which is also reflected in the increased basophilic cell percentage in gerbil (control: 15.5 percent; methallibure: 22.8 percent). 5. It is concluded that methallibure acts on thyroid function both by a direct effect on the gland as well as by influencing pituitary thyrotrophic activity in enhancing I131 uptake.
Gonadotrophin content in the pituitary gland and blood serum as well as ovarian 32P uptake were studied in response to methallibure treatment in H. fossilis. There was a marked reduction in the gonadotrophic activity of the pituitary gland and blood serum within 3 weeks of methallibure treatment (100 microng/g). A simultaneous significant reduction was also recorded in the ovarian activity of these fish. The fall in ovarian activity caused by methallibure could not be prevented by the administration of LH, FSH or LH+FSH. After cessation of methallibure treatment, LH+FSH (50 microng each) administration restored ovarian activity. It is evident from these results that methallibure alters the secretion of gonadotrophin, and also prevents its action on the ovary.
1. Synergistic action of alpha-chlorohydrin with methallibure (ICI, 33828) on the testicular function of Presbytis entellus entellus Dufresne has been studied. 2. Chronic administration of alpha-chlorohydrin alone (140 mg/day for 40 days) caused testicular lesion resulting in a massive atrophy of the spermatogenic elements. Epididymal epithelium was regressed and the lumen was devoid of spermatozoa. 3. alpha-Chlorohydrin inhibited the synthesis of RNA and sialic acid in the testes and epididymides. Total cholesterol per gram of testis and alkaline phosphatase activity were increased after alpha-chlorohydrin administration. 4. These effects could be achieved with a lower dose of alpha-chlorohydrin (1/4) when administered in combination with a gonadotrophin inhibitor, i. e. ICI, 33828 (Methallibure). Methallibure alone (200 mg/kg: total dose) has no damaging effects on the testes and epididymides. But it altered testicular cholesterol and enzyme activity. 5. In conclusion, an effective inhibition of spermatogenesis could be achieved by synergistic action of the two different drugs i. e. alpha-chlorohydrin and ICI, 33828 (Methallibure).
Methallibure administration caused reduction of gonadal weights in female rats and mice indicative of suppression of pituitary gonadotrophins. In the ovaries of the methallibure treated females, there was a great atresia of the follicles and of the corpora lutea. Methalbure caused atrophic changes in the endometrial lining of the vagina. Uterine horns became thin after methallibure treatment. A significant decrease in protein, RNA and sialic acid concentration in uterus and vagina was observed following methallibure treatment. Uterus of treated animals showed decreased glycogen contents. Histological and biochemical changes in the female genital tract of rats and mice suggested that the drug caused antifertility effect due to its possible antiestrogenic action.
Effects of methallibure (I.C.I. 33828) have been studied on the reproductive organs of female gerbils, Meriones hurrianae. Methallibure administration caused reduction of gonadal weight indicating suppression of pituitary gonadotrophins. In the ovaries of the treated females extensive atresia of follicles and of corpora lutea was observed. In addition methallibure interrupted the sex cycle, and a dioestrous vaginal pattern was retained throughout medication. A significant decrease in the level of RNA, protein and sialic acid in the uterus and vagina and of glycogen in the uterus was found. Histological and biochemical changes in the ovaries and uteri suggest a possible direct antioestrogenic action of the compound.
The effect of methallibure (ICI 33,828) on the pituitary-gonad and the pituitary-thyroid axes of the Indian garden lizard, Calotes veriscolor was studied. Following administration of methallibure B2 (FSH) and B3 (ICSH) cells of the pars distalis exhibited significant alterations with concomitant changes in the seminiferous tubules, and in the interstitial cells and epididymis respectively. B1 (TSH) cells exhibited conspicuous hypertrophy and degranulation which was reflected in dramatic changes in thyroid morphology. The caudally localized acidophilic A1 (PRL) cells also showed hypertrophy, hyperplasia and intense granulation. The rostrally located A2 (STH) acidophils and the B4 (ACTH) cells were unaffected by the treatment. The possible model of action of this drug is discussed in the light of available literature.
Methallibure treatment is as effective as hypophysectomy in reducing thyroid activity in H. fossilis. Sex steroids (TP and EB) administration restored thyroid activity in methallibure-treated females to normal level, but failed to elicit any response in males. This drug seems to block TSH secretion and thyroid hormone synthesis in H. fossilis.
Daily administration of 10 mg of Methallibure (ICI 33,828) for 6 days to male castrate rats resulted in significant depression of serum radioimmunoassayable luteinizing hormone (LH). Subsequent challenge with 100 ng of synthetic luteinizing hormone-releasing hormone (LHRH) showed these rats to release sufficient pituitary LH to achieve plasma levels equal to those of LHRH treated castrate controls. Although an effect at the level of the pituitary remains to be conclusively ruled out, these results suggest that the predominant in vivo effect of Methallibure in the castrate male rat is to suppress pituitary LH release due to diminished secretion of LHRH by the hypothalamus.
Methallibure treatment of mature Cyprinus carpio causes a marked reduction in the steroidogenesis, as indicated by the fall in 3beta-HSD activity in the gonads. Significance of these results is discussed.
The effect of methallibure on ovary of H. fossilis was studied. Intraperitoneal administration of methalibure (100 microgram/g body weight) once a week for 4 weeks was very effective in suppressing the gametogenic and endocrine activities of ovary. The regressed condition of ovary was also apparent in GSI (2.84 to 1.09) readings. This decreased state of activity was further confirmed by reduced ovarian 32P uptake (28.00 to 18.10). The results obtained after the administration of the above compound on ovary were similar to those of surgical hypophysectomy.
Variations in the prolactin content of the pituitary gland in response to different treatments were studied in a freshwater catfish, H. fossilis. One week of saline (1% NaCl medium) treatment reduced the pituitary prolactin content but enhanced the serum prolactin level showing release of prolactin from the pituitary gland. Two weeks of saline treatment reduced pituitary as well as serum prolactin content presumably a result of reduced prolactin synthesis in the pituitary gland. This reduction of synthetic activity in this species is probably due to a drop in prolactin requirement. All the antithyroid durgs tested as well as L-thyroxine decreased the pituitary prolactin content. Methallibure administration induced the release of prolactin from the pituitary as evidenced by the lowered prolactin level in this gland and a simultaneous increase in the prolactin content of the serum.
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