Abstract
The pars tuberalis of the hypophysis of the Djungarian hamster, Phodopus sungorus, was investigated with regard to secretory activity by applying the tannic acid-Ringer perfusion technique. Two groups were maintained under long photoperiods (16 h light: 8 h dark) or short photoperiods (8 h light: 16 h dark), respectively. Perfusion with tannic acid showed that specific pars tuberalis cells release some of their secretory granules as indicated by typical exocytotic figures. The percentage of cells displaying exocytotic activity was significantly higher in the pars tuberalis of hamsters kept under long photoperiods. The number of exocytotic figures per single cell was not increased. These results provide further evidence for a secretory activity of the pars tuberalis and support the hypothesis of its involvement as a mediator between photoperiodic stimuli and the endocrine system.
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References
Buma PR, Nieuwenhuys R (1988) Ultrastructural characterization of exocytotic release sites in different layers of the median eminence of the rat. Cell Tissue Res 252:107–114
Champney TH (1990) Propanolol blockade of short photoperiod-induced gonadal regression: modification by melatonin injections or implants. J Pineal Res 9:75–83
Dellmann HD, Stoeckel ME, Hindelang-Gertner C, Porte A, Stutinsky F (1974) A comparative ultrastructural study of the pars tuberalis of various mammals, the chicken and the newt. Cell Tissue Res 148:313–329
Forsberg M, Madej A (1990) Effects of melatonin implants on plasma concentrations of testosterone, thyroxine and prolactin in the male silver fox (Vulpes vulpes). J Reprod Fertil 89:351–358
Hegarty CM, Jonassen JA, Bittmann EL (1990) Pituitary hormone gene expression in male golden hamsters: interactions between photoperiod and testosterone. J Neuroendocrinol 2:567–573
Hoffmann K (1982) The effect of brief light pulses on the photoperiodic reaction in the Djungarian hamster Phodopus sungorus. J Comp Physiol 148:529–534
Laitinen JT, Saavedra JM (1990) Characterization of melatonin receptors in the rat suprachiasmatic nuclei: modulation of affinity with cations and guanine nucleotides. Endocrinology 126:2110–2115
Morgan DJ, Lawson W, Davidson G, Howell HE (1989) Guanine nucleotides regulate the affinity of melatonin receptors on the ovine pars tuberalis. Neuroendocrinology 50:359
Pelletier J, Castro B, Roblot G, Wylde R, Reviers MM de (1990) Characterization of melatonin receptors in the ram pars tuberalis: influence of light. Acta Endocrinol 123:557–562
Rose J, Stormshak F, Oldfield J, Adair J (1985) The effect of photoperiod and melatonin on serum prolactin levels. J Pineal Res 2:13–19
Rütten A, Hewing M, Wittkowski W (1988) Seasonal ultrastructural changes of the hypophysial pars tuberalis in the hedgehog (Erinaceus europaeus L.) Acta Anat (Basel) 133:217–223
Stankov B, Cozzi B, Lucini V, Fumagalli P, Scaglione F, Fraschini F (1991) Characterization and mapping of melatonin receptors in the brain of three mammalian species: rabbit, horse and sheep. Neuroendocrinology 53:214–221
Steger RW, Bartke A (1991) Temporal sequence of neuroendocrine events associated with the transfer of male golden hamsters from a stimulatory to a nonstimulatory photoperiod. Biol Reprod 44:76–82
Steger RW, Dennis C, Van Abbema A, Gay-Primel E (1990) Alterations in hypothalamic serotonin metabolism in male hamsters with photoperiod-induced testicular regression. Brain Res 514:11–14
Stoeckel ME, Porte A (1984) Fine structure and development of the pars tuberalis in mammals. In: Motta PM (ed) Ultrastructure of endocrine cells and tissues. Nijhoff, Boston, pp 29–38
Vriend J, Richardson BA, Vaughan MK, Johnson LY, Reiter RJ (1982) Effects of melatonin on thyroid physiology of female hamsters. Neuroendocrinology 35:79–85
Weaver DR, Reppert SM (1990) Melatonin receptors are present in the ferret pars tuberalis and the pars distalis, but not in brain. Endocrinology 127:2607–2609
Williams LM, Morgan PJ (1988) Demonstration of melatonin-binding sites of the pars tuberalis of the rat. J Endocrinol 119:R1-R3
Wittkowski W, Hewing M, Hoffmann K, Bergmann M, Fechner J (1984) Influence of photoperiod on the ultrastructure of the hypophysial pars tuberalis of the Djungarian hamster, Phodopus sungorus. Cell Tissue Res 238:213–216
Wittkowski W, Bergmann M, Hoffmann K, Pera F (1988) Photoperiod-dependent changes in TSH-like immunoreactivity of cells in the hypophysial pars tuberalis of the Djungarian hamster, Phodopus sungorus. Cell Tissue Res 251:183–187
Wittkowski W, Schulze-Bonhage A, Böckers T (1992) The pars tuberalis of the hypophysis: a modulator of the pars distalis? Acta Endocrinol (Copenh) 126:285–290
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Merks, T., Schulze-Bonhage, A. & Wittkowski, W. Photoperiod-dependent changes in exocytotic activity in the hypophyseal pars tuberalis of the Djungarian hamster, Phodopus sungorus . Cell Tissue Res 273, 287–291 (1993). https://doi.org/10.1007/BF00312830
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DOI: https://doi.org/10.1007/BF00312830