EFFECT OF TAMOXIFEN ON PITUITARY VASOPRESSIN LEVEL
AbstractBackground: Estrogens modulate the release of Arginine Vasopressin (AVP). There is an increased level of AVP in plasma and pituitary under osterogen hormones. Methods: Ten rats were experimental and ten were controls. The ten experimental rats were injected tamoxifen daily subcutaneously for three days in does of 1 mg/kg body weight in 0.1 ml vegetable oil base. The ten control rats were given 0.1 ml of vegetable oil vehicle only subcutaneously. On the morning of the fourth day all the twenty rats were decapitated. Blood was centrifuged at 2500 rev/min for 15 min at 40C. Plasma was stored at –20oC for assay of AVP. Pituitary gland was removed and homogenized in a test tube containing 1 ml of 0.2 molar acetic acid & stored at –20oC for analysis of pituitary AVP. Uteri of all rats were removed by careful dissection & weighed. Results: Uterine weight and plasma AVP levels were decreased but the pituitary AVP level was unaffected. Conclusion:Under Tamoxifen (anti-estrogen) effect the plasma vasopressin decreased but the level in the posterior was not affected. The effect of osterogen on Hypothalamo Pituitary axis (HPA is measurable in the hypothalamus therefore probably anti-oestrogenic effect would operate more at hypothalamic level rather than posterior pituitary. This needs further investigation at the Hypothalamus level.Key Words: Vasopressin, Tamoxifen, Pituitary
Butcher RL, Collins WE, Fugo NW. Plasma concentrations of LH, FSH, prolactin, progesterone and oestradiol throughout the 4-day oestrous cycle of the rat. Endocrinology 1974;94:1704-7.
De Vries GJ, Buijs RM, Sluiter AA. Gonadal hormone action on the morphology of the vaspressinergic innervation of the adult rat brain. Brain Research 1984;298:141-5.
Durr JA, Stamoutsos BA, Lindheimer MD.Journal of Clinical Investigation 1981;68: 337-46
Crowley WA, Donohue TL, George GM, Jacobowitz DM. Changes in pituitary oxytocin and vasopressin during the oes-trous cycle and after ovarian hormones: Evidence for medi-ation by norepinephrine. Life Sciences 1978;23:2579-86.
Skowsky WR, Swan L, Smith P. Effects of sex steroid hormones on arginine vasopressin inintact and castrated male and female rats. Endocrinology 1979;104:105-106.
Swabb DF, Jongkind OF. The hypothalamic neurosecretory activity during the estrous cycle, pregnancy, parturition and persistent estrous after gonadectomy in the rat. Neuroendocrinology 1970;6:133-145.
Barron WM, Schreiber J, Lindheimer MD. Effect of ovarian sex steroids on osmoregulation and vasopressin secretion in the rat. Endocrine Metab. American Journal of Physiology 1986;250: E352-E361.
Rhodes CH, Morrell JI, Pfaff DW. Distribution of estrogen-concentration neurophysin-containing magnocellular neurons in the rat hypothalamus as demonstrated by a technique com-bining steroid autoradiography and immuno-histochemistry in the same tissue. Neuroendocrinology 1981;33,18-23
Sar M, Stumpf WE. Simultaneous localization of Hestradiol and neurophysin I or orginine vasopressin in hypothalamic neurons demonstrated by a combined technique
Negoro HS, Visessuwan S, Holland RC. Reflex activation of paraventricular nucleus units during the reproductive cycle and in ovaariectomized rats treated with oestroges or progesterone. J Endocrinol 1973;59:559-67
Grant LD, Stumpf WE. Hormone uptake sites in relation to central nervous sysem biogenic amine systems. In: Anatomical Neuroendocrinology. Basel: Karger 1975.
Heritage AS, Stumpf WE, Sar M, Grant LD. Brainstem catecholamine neurons are target sites for sex steroid hormones. Science 1980;207:1377-9.
Husain, M. K, Manger WM, Rock TW, Weiss RJ, Frantz AG. “Vasopressin release due to manual restraint in the rat: role of body compression and comparison with other stressful stimuli”. Endocrinology 1979;104:641-4.
Watches DC, Swann RW, Birkett SD, Porter DG, Pickering BT. Characterization of oxytoein, vasopressin and neurophysin from the bovine corpus luteum. Endocrinology 1983;113:693-8.
Barnafi L, Croxatto H. Vasopressin and oxytocic activities in the posterior lobe of the pituitary gland of male and female rats following adrenalectomy and gonadectomy. Acta Endorinologicu 1966;52, 3-6.
Khan MA, Khan MA, Aslam M. Food intake and water retention over the oestrus cycle of the rat treated with difluormethylornithine (DFMO). 1995
Arima H, Kondo K, Murase T, Yokoi H, Iwasaki Y, Saito H, Oiso Y. Regulation of vasopressin synthesis and release by area postrema in rats. Endocrinology 1998;139(4):1481-6.
Wood CE, Saoud CJ, Stoner TA, Keller-Wood M. Estrogen and androgen influence hypothalamic AVP and CRF concentrations in fetal and adult sheep. Regul Pept. 2001;98(1-2):63-8.
Hartley DE, Dickson SL, Forsling ML. Plasma vasopressin concentrations and Fos protein expression in the supraoptic nucleus following osmotic stimulation or hypovolaemia in the ovariectomized rat: effect of oestradiol replacement. J Neuroendocrinol. 2004;16(3):191-7.